WikiVet English - User contributions [en]

Veterinary Education Online

2024-08-30T08:40:50Z

Roytwv:

__NOTOC__
<templatestyles src="Main Page/styles.css" />
<div id="mp-topbanner" class="mp-bordered">
<div id="mp-welcomecount">
<div id="mp-welcome">Welcome to [[Main Page|WikiVet]],</div>
<div id="mp-free">Free [[WikiVet Introduction|veterinary encyclopedia]]. [[Frequently_Asked_Questions#How_do_I_edit_content|Submissions welcome]]<br>and are reviewed by renowned veterinary professionals.</div>
<div id="articlecount">[[Special:Statistics|{{NUMBEROFARTICLES}}]] articles in English</div>
</div>
<ul id="mp-portals">
<li>[[CPD Events]]</li>
<li class="portal-vmid">[[Discipline]]s</li>
<li class="portal-vbot">[[Learning Resources|Learning]]</li>
<li class="portal-hmid">[[Lectures]]</li>
<li class="portal-hmid portal-vmid">[[Podcasts]]</li>
<li class="portal-hmid portal-vbot">[[Species]]</li>
<li class="portal-hright">[[System]]</li>
<li class="portal-hright portal-vmid">[https://thewebinarvet.com/videos?utm_source=wikivet&utm_medium=referral&utm_campaign=webinars Webinars]</li>
<li class="portal-hright portal-vbot">[[Video]]s</li>
</ul>
</div>

<div class="MainPageBG" style="border:1px solid #5B9DA7; background:#f5faff; color:#000; padding:0 14px 8px; margin-top:7px;">
== Join the Veterinary Student Room Community ==

This Student Room is dedicated to veterinary students from all over the world. Whether you’re in your first year or preparing for your final exams, this is your place to connect, learn, and grow. Here’s what you can do:

* '''Ask for Help''': If you’re stuck on a topic or need advice on study techniques, just ask!
* '''Share Resources''': Exchange notes, study guides, and useful links with fellow students.
* '''Get Career Advice''': Seek guidance on internships, job applications, and career paths.
* '''Connect with Peers''': Make friends, form study groups, and support each other through your studies.

Your journey through veterinary school is challenging but incredibly rewarding. We’re here to help you succeed and make the most of your student experience. Brought to you by The Webinar Vet.

'''<big><u>[https://thewebinarvet.com/community Join the Student Room]</u></big>'''

== Explore Over 3,000 Veterinary Webinars ==

Elevate your veterinary expertise with The Webinar Vet. Explore over 30 specialised veterinary fields, including:

''<small>Anaesthesia and Analgesia, Antimicrobial Resistance, Behaviour, Cardiology, Clinical Anatomy, Clinical Pathology, Dentistry, Dermatology, Diagnostic Imaging, Emergency and Critical Care, Endocrinology, Gastroenterology and Nutrition, Herd Health, Infection Control and Biosecurity, Internal Medicine, Neurology, Oncology, Ophthalmology, Orthopaedics, Parasitology, Personal Development and Wellbeing, Pharmacology, Rehabilitation and Physiotherapy, Respiratory, Soft Tissue Surgery, Surgery, Sustainability, Urogenital and Reproduction, Welfare and Ethics, Wound Management, and Youngstock.</small>''

Sign up today to take advantage of our discounted student membership, giving you unlimited access to expert knowledge across all these areas.

'''<big><u>[https://thewebinarvet.com/videos?utm_source=wikivet&utm_medium=referral&utm_campaign=videos View Webinars]</u></big>'''

== Upcoming Veterinary Events ==

Explore our comprehensive selection of online veterinary events, including live webinars and on-demand sessions. Enhance your professional skills and knowledge at your convenience.

'''<big><u>[https://thewebinarvet.com/events?utm_source=wikivet&utm_medium=referral&utm_campaign=events View Veterinary Events]</u></big>'''

== Veterinary Courses ==

Unlock your potential with our comprehensive veterinary courses designed to help you excel in your field. Whether you're looking to deepen your knowledge or expand your skillset, our expert-led courses cover a wide range of topics to support your professional growth.

'''<big><u>[https://thewebinarvet.com/courses?utm_source=wikivet&utm_medium=referral&utm_campaign=courses Veterinary Courses]</u></big>'''

== Veterinary Podcasts ==

Tune in to the #1 veterinary podcast in Europe, where we explore the latest insights, trends, and expert advice across the veterinary world. With new episodes released every week, there's always something fresh to discover.

'''<big><u>[https://thewebinarvet.com/videos/category/podcast Visit VETchat]</u></big>'''

</div>

[[es:Página Principal]]
[[fr:Accueil]]

Veterinary Education Online

2024-08-27T12:19:41Z

Roytwv:

__NOTOC__
<templatestyles src="Main Page/styles.css" />
<div id="mp-topbanner" class="mp-bordered">
<div id="mp-welcomecount">
<div id="mp-welcome">Welcome to [[Main Page|WikiVet]],</div>
<div id="mp-free">Free [[WikiVet Introduction|veterinary encyclopedia]]. [[Frequently_Asked_Questions#How_do_I_edit_content|Submissions welcome]]<br>and are reviewed by renowned veterinary professionals.</div>
<div id="articlecount">[[Special:Statistics|{{NUMBEROFARTICLES}}]] articles in English</div>
</div>
<ul id="mp-portals">
<li>[[CPD Events]]</li>
<li class="portal-vmid">[[Discipline]]s</li>
<li class="portal-vbot">[[Learning Resources|Learning]]</li>
<li class="portal-hmid">[[Lectures]]</li>
<li class="portal-hmid portal-vmid">[[Podcasts]]</li>
<li class="portal-hmid portal-vbot">[[Species]]</li>
<li class="portal-hright">[[System]]</li>
<li class="portal-hright portal-vmid">[https://thewebinarvet.com/videos?utm_source=wikivet&utm_medium=referral&utm_campaign=webinars Webinars]</li>
<li class="portal-hright portal-vbot">[[Video]]s</li>
</ul>
</div>

<div class="MainPageBG" style="border:1px solid #5B9DA7; background:#f5faff; color:#000; padding:0 14px 8px; margin-top:7px;">
== Join the Veterinary Student Room Community ==

This Student Room is dedicated to veterinary students from all over the world. Whether you’re in your first year or preparing for your final exams, this is your place to connect, learn, and grow. Here’s what you can do:

* '''Ask for Help''': If you’re stuck on a topic or need advice on study techniques, just ask!
* '''Share Resources''': Exchange notes, study guides, and useful links with fellow students.
* '''Get Career Advice''': Seek guidance on internships, job applications, and career paths.
* '''Connect with Peers''': Make friends, form study groups, and support each other through your studies.

Your journey through veterinary school is challenging but incredibly rewarding. We’re here to help you succeed and make the most of your student experience. Brought to you by The Webinar Vet.

'''[https://community.thewebinarvet.com/c/student-room/ <big><u>Join the Student Room</u></big>]'''

== Explore Over 3,000 Veterinary Webinars ==

Elevate your veterinary expertise with The Webinar Vet. Explore over 30 specialised veterinary fields, including:

''<small>Anaesthesia and Analgesia, Antimicrobial Resistance, Behaviour, Cardiology, Clinical Anatomy, Clinical Pathology, Dentistry, Dermatology, Diagnostic Imaging, Emergency and Critical Care, Endocrinology, Gastroenterology and Nutrition, Herd Health, Infection Control and Biosecurity, Internal Medicine, Neurology, Oncology, Ophthalmology, Orthopaedics, Parasitology, Personal Development and Wellbeing, Pharmacology, Rehabilitation and Physiotherapy, Respiratory, Soft Tissue Surgery, Surgery, Sustainability, Urogenital and Reproduction, Welfare and Ethics, Wound Management, and Youngstock.</small>''

Sign up today to take advantage of our discounted student membership, giving you unlimited access to expert knowledge across all these areas.

'''<big><u>[https://thewebinarvet.com/videos?utm_source=wikivet&utm_medium=referral&utm_campaign=videos View Webinars]</u></big>'''

== Upcoming Veterinary Events ==

Explore our comprehensive selection of online veterinary events, including live webinars and on-demand sessions. Enhance your professional skills and knowledge at your convenience.

'''<big><u>[https://thewebinarvet.com/events?utm_source=wikivet&utm_medium=referral&utm_campaign=events View Veterinary Events]</u></big>'''

== Veterinary Courses ==

Unlock your potential with our comprehensive veterinary courses designed to help you excel in your field. Whether you're looking to deepen your knowledge or expand your skillset, our expert-led courses cover a wide range of topics to support your professional growth.

'''<big><u>[https://thewebinarvet.com/courses?utm_source=wikivet&utm_medium=referral&utm_campaign=courses Veterinary Courses]</u></big>'''

== Veterinary Podcasts ==

Tune in to the #1 veterinary podcast in Europe, where we explore the latest insights, trends, and expert advice across the veterinary world. With new episodes released every week, there's always something fresh to discover.

'''<big><u>[https://thewebinarvet.com/videos/category/podcast Visit VETchat]</u></big>'''

</div>

[[es:Página Principal]]
[[fr:Accueil]]

Veterinary Education Online

2024-05-21T16:09:04Z

Roytwv:

Veterinary Education Online

2024-04-02T08:59:29Z

Roytwv: Modeus Webinar

__NOTOC__
<templatestyles src="Main Page/styles.css" />
<div id="mp-topbanner" class="mp-bordered">
<div id="mp-welcomecount">
<div id="mp-welcome">Welcome to [[Main Page|WikiVet]],</div>
<div id="mp-free">Free [[WikiVet Introduction|veterinary encyclopedia]]. [[Frequently_Asked_Questions#How_do_I_edit_content|Submissions welcome]]<br>and are reviewed by renowned veterinary professionals.</div>
<div id="articlecount">[[Special:Statistics|{{NUMBEROFARTICLES}}]] articles in English</div>
</div>
<ul id="mp-portals">
<li>[[CPD Events]]</li>
<li class="portal-vmid">[[Discipline]]s</li>
<li class="portal-vbot">[[Learning Resources|Learning]]</li>
<li class="portal-hmid">[[Lectures]]</li>
<li class="portal-hmid portal-vmid">[[Podcasts]]</li>
<li class="portal-hmid portal-vbot">[[Species]]</li>
<li class="portal-hright">[[System]]</li>
<li class="portal-hright portal-vmid">[https://thewebinarvet.com/videos?utm_source=wikivet&utm_medium=referral&utm_campaign=webinars Webinars]</li>
<li class="portal-hright portal-vbot">[[Video]]s</li>
</ul>
</div>

<div class="MainPageBG" style="border:1px solid #5B9DA7; background:#f5faff; color:#000; padding:0 14px 8px; margin-top:7px;">[[File:Burgess Excel - 1405.jpg|alt=Virtual Veterinary Conference 2024|left|thumb|300x300px|[https://thewebinarvet.com/webinars/revolutionising-controlled-drug-management-in-veterinary-practice?utm_source=wikivet&utm_medium=referral&utm_campaign=homepage]]]

== Register for FREE: Revolutionising controlled drug management in veterinary practice ==

Join our free webinar for key insights into managing controlled drugs in the veterinary industry. We'll cover the challenges of drug misuse, the limitations of paper registers, and how digital solutions like Vet S8 software can revolutionize compliance and efficiency. Learn about the importance of controlled drug recording and discover software that enhances governance over traditional methods. An interactive Q&A session will conclude the event, offering personalized advice.

'''[https://thewebinarvet.com/webinars/revolutionising-controlled-drug-management-in-veterinary-practice?utm_source=wikivet&utm_medium=referral&utm_campaign=homepage Register for FREE today!]'''

[[File:Start Your 7-Day Free Trial.jpg|alt=The Webinar Vet Free Trial|left|thumb]]

== Access 2,500 Veterinary CE Videos | Start Your 7-Day Risk Free Trial ==

Introducing The Webinar Vet, the groundbreaking CE platform that's revolutionizing the veterinary industry! Are you looking to maintain your CE progress effortlessly? The Webinar Vet has got your back. Seeking an easy way to download your CE certificates? Absolutely, that's covered too.

The Webinar Vet offers webinars and podcasts that are not just informative but also compatible across various devices. Whether you're on a tablet, smartphone, or computer, you can start watching on one device and continue seamlessly on another, ensuring you never miss a critical detail during transitions.

There's more to discover! The Webinar Vet's webinars are enriched with detailed synopses, release notes, and some even include interactive Q&A sessions. This ensures you gain the most from your CE experience. With new webinars and podcasts introduced weekly by leading experts, you're guaranteed a continuous stream of up-to-date veterinary knowledge.

[https://thewebinarvet.com/memberships?utm_source=wikivet&utm_medium=referral&utm_campaign=homepage '''Start Your 7-Day Free Trial Today!''']

</div>

[[es:Página Principal]]
[[fr:Accueil]]

File:Burgess Excel - 1405.jpg

2024-04-02T08:55:41Z

Roytwv:

Burgess Excel Webinar

Veterinary Education Online

2023-12-18T12:32:03Z

Roytwv:

__NOTOC__
<templatestyles src="Main Page/styles.css" />
<div id="mp-topbanner" class="mp-bordered">
<div id="mp-welcomecount">
<div id="mp-welcome">Welcome to [[Main Page|WikiVet]],</div>
<div id="mp-free">Free [[WikiVet Introduction|veterinary encyclopedia]]. [[Frequently_Asked_Questions#How_do_I_edit_content|Submissions welcome]]<br>and are reviewed by renowned veterinary professionals.</div>
<div id="articlecount">[[Special:Statistics|{{NUMBEROFARTICLES}}]] articles in English</div>
</div>
<ul id="mp-portals">
<li>[[CPD Events]]</li>
<li class="portal-vmid">[[Discipline]]s</li>
<li class="portal-vbot">[[Learning Resources|Learning]]</li>
<li class="portal-hmid">[[Lectures]]</li>
<li class="portal-hmid portal-vmid">[[Podcasts]]</li>
<li class="portal-hmid portal-vbot">[[Species]]</li>
<li class="portal-hright">[[System]]</li>
<li class="portal-hright portal-vmid">[https://thewebinarvet.com/videos?utm_source=wikivet&utm_medium=referral&utm_campaign=webinars Webinars]</li>
<li class="portal-hright portal-vbot">[[Video]]s</li>
</ul>
</div>

<div class="MainPageBG" style="border:1px solid #5B9DA7; background:#f5faff; color:#000; padding:0 14px 8px; margin-top:7px;">[[File:Vvc24-wiki.jpg|alt=Virtual Veterinary Conference 2024|left|thumb|300x300px]]

== Register for FREE: Virtual Veterinary Conference 2024 ==

Embark on an enticing journey through pet healthcare, exploring intriguing guinea pig diseases, practical strategies for cat-friendly clinics, and interactive ophthalmology cases. Deep-dive into neurological emergencies through dynamic case videos. Discover rabbit urinary tract diseases, decode the behaviour of confrontational cats, understand the rising trend of ocular disease in brachycephalic dogs, and tackle the challenge of spinal pain in young dogs.

A compelling exploration tailored for vets from anywhere in the world, primed to spark your curiosity and reignite your passion for animal care.

''Also known as: Virtual Congress, VC24, VVC24, and Virtual Congress 2024.''

[https://thewebinarvet.com/events/virtual-veterinary-congress-2024?utm_source=wikivet&utm_medium=referral&utm_campaign=homepage '''Register for FREE today!''']

[[File:Start Your 7-Day Free Trial.jpg|alt=The Webinar Vet Free Trial|left|thumb]]

== Access 2,500 Veterinary CE Videos | Start Your 7-Day Risk Free Trial ==

Introducing The Webinar Vet, the groundbreaking CE platform that's revolutionizing the veterinary industry! Are you looking to maintain your CE progress effortlessly? The Webinar Vet has got your back. Seeking an easy way to download your CE certificates? Absolutely, that's covered too.

The Webinar Vet offers webinars and podcasts that are not just informative but also compatible across various devices. Whether you're on a tablet, smartphone, or computer, you can start watching on one device and continue seamlessly on another, ensuring you never miss a critical detail during transitions.

There's more to discover! The Webinar Vet's webinars are enriched with detailed synopses, release notes, and some even include interactive Q&A sessions. This ensures you gain the most from your CE experience. With new webinars and podcasts introduced weekly by leading experts, you're guaranteed a continuous stream of up-to-date veterinary knowledge.

[https://thewebinarvet.com/memberships?utm_source=wikivet&utm_medium=referral&utm_campaign=homepage '''Start Your 7-Day Free Trial Today!''']

</div>

[[es:Página Principal]]
[[fr:Accueil]]

CPD Events

2023-12-18T12:29:04Z

Roytwv: /* Virtual Congress 2024 */

== Virtual Events brought to you by The Webinar Vet ==
We are proud to help the veterinary community access CPD/CE conferences and events online from all over the world.

All of the following events are available to view online, either live, or as webinar recordings you can view at your own convenience.

=== '''[https://thewebinarvet.com/events/virtual-veterinary-congress-2024?utm_source=wikivet&utm_medium=referral&utm_campaign=vc2024 Virtual Veterinary Congress 2024 | 5th-9th February 2024]''' ===
Embark on an enticing journey through pet healthcare, exploring intriguing guinea pig diseases, practical strategies for cat-friendly clinics, and interactive ophthalmology cases. Deep-dive into neurological emergencies through dynamic case videos. Discover rabbit urinary tract diseases, decode the behaviour of confrontational cats, understand the rising trend of ocular disease in brachycephalic dogs, and tackle the challenge of spinal pain in young dogs.

A compelling exploration tailored for vets from anywhere in the world, primed to spark your curiosity and reignite your passion for animal care.

'''[https://thewebinarvet.com/events/virtual-veterinary-congress-2024?utm_source=wikivet&utm_medium=referral&utm_campaign=events Register For Free Today!]'''

Veterinary Education Online

2023-12-18T12:26:21Z

Roytwv:

__NOTOC__
<templatestyles src="Main Page/styles.css" />
<div id="mp-topbanner" class="mp-bordered">
<div id="mp-welcomecount">
<div id="mp-welcome">Welcome to [[Main Page|WikiVet]],</div>
<div id="mp-free">Free [[WikiVet Introduction|veterinary encyclopedia]]. [[Frequently_Asked_Questions#How_do_I_edit_content|Submissions welcome]]<br>and are reviewed by renowned veterinary professionals.</div>
<div id="articlecount">[[Special:Statistics|{{NUMBEROFARTICLES}}]] articles in English</div>
</div>
<ul id="mp-portals">
<li>[[CPD Events]]</li>
<li class="portal-vmid">[[Discipline]]s</li>
<li class="portal-vbot">[[Learning Resources|Learning]]</li>
<li class="portal-hmid">[[Lectures]]</li>
<li class="portal-hmid portal-vmid">[[Podcasts]]</li>
<li class="portal-hmid portal-vbot">[[Species]]</li>
<li class="portal-hright">[[System]]</li>
<li class="portal-hright portal-vmid">[https://www.thewebinarvet.com/?utm_source=wikivet&utm_medium=webinar_hp_link Webinars]</li>
<li class="portal-hright portal-vbot">[[Video]]s</li>
</ul>
</div>

<div class="MainPageBG" style="border:1px solid #5B9DA7; background:#f5faff; color:#000; padding:0 14px 8px; margin-top:7px;">[[File:Vvc24-wiki.jpg|alt=Virtual Veterinary Conference 2024|left|thumb|300x300px]]

== Register for FREE: Virtual Veterinary Conference 2024 ==

Embark on an enticing journey through pet healthcare, exploring intriguing guinea pig diseases, practical strategies for cat-friendly clinics, and interactive ophthalmology cases. Deep-dive into neurological emergencies through dynamic case videos. Discover rabbit urinary tract diseases, decode the behaviour of confrontational cats, understand the rising trend of ocular disease in brachycephalic dogs, and tackle the challenge of spinal pain in young dogs.

A compelling exploration tailored for vets from anywhere in the world, primed to spark your curiosity and reignite your passion for animal care.

''Also known as: Virtual Congress, VC24, VVC24, and Virtual Congress 2024.''

[https://thewebinarvet.com/events/virtual-veterinary-congress-2024?utm_source=wikivet&utm_medium=referral&utm_campaign=homepage '''Register for FREE today!''']

[[File:Start Your 7-Day Free Trial.jpg|alt=The Webinar Vet Free Trial|left|thumb]]

== Access 2,500 Veterinary CE Videos | Start Your 7-Day Risk Free Trial ==

Introducing The Webinar Vet, the groundbreaking CE platform that's revolutionizing the veterinary industry! Are you looking to maintain your CE progress effortlessly? The Webinar Vet has got your back. Seeking an easy way to download your CE certificates? Absolutely, that's covered too.

The Webinar Vet offers webinars and podcasts that are not just informative but also compatible across various devices. Whether you're on a tablet, smartphone, or computer, you can start watching on one device and continue seamlessly on another, ensuring you never miss a critical detail during transitions.

There's more to discover! The Webinar Vet's webinars are enriched with detailed synopses, release notes, and some even include interactive Q&A sessions. This ensures you gain the most from your CE experience. With new webinars and podcasts introduced weekly by leading experts, you're guaranteed a continuous stream of up-to-date veterinary knowledge.

[https://thewebinarvet.com/memberships?utm_source=wikivet&utm_medium=referral&utm_campaign=homepage '''Start Your 7-Day Free Trial Today!''']

</div>

[[es:Página Principal]]
[[fr:Accueil]]

Veterinary Education Online

2023-12-18T12:24:49Z

Roytwv:

__NOTOC__
<templatestyles src="Main Page/styles.css" />
<div id="mp-topbanner" class="mp-bordered">
<div id="mp-welcomecount">
<div id="mp-welcome">Welcome to [[Main Page|WikiVet]],</div>
<div id="mp-free">Free [[WikiVet Introduction|veterinary encyclopedia]]. [[Frequently_Asked_Questions#How_do_I_edit_content|Submissions welcome]]<br>and are reviewed by renowned veterinary professionals.</div>
<div id="articlecount">[[Special:Statistics|{{NUMBEROFARTICLES}}]] articles in English</div>
</div>
<ul id="mp-portals">
<li>[[CPD Events]]</li>
<li class="portal-vmid">[[Discipline]]s</li>
<li class="portal-vbot">[[Learning Resources|Learning]]</li>
<li class="portal-hmid">[[Lectures]]</li>
<li class="portal-hmid portal-vmid">[[Podcasts]]</li>
<li class="portal-hmid portal-vbot">[[Species]]</li>
<li class="portal-hright">[[System]]</li>
<li class="portal-hright portal-vmid">[https://www.thewebinarvet.com/?utm_source=wikivet&utm_medium=webinar_hp_link Webinars]</li>
<li class="portal-hright portal-vbot">[[Video]]s</li>
</ul>
</div>

<div class="MainPageBG" style="border:1px solid #5B9DA7; background:#f5faff; color:#000; padding:0 14px 8px; margin-top:7px;">[[File:Vvc24-wiki.jpg|alt=Virtual Veterinary Conference 2024|left|thumb|300x300px]]

== Register for FREE: Virtual Veterinary Conference 2024 ==

Embark on an enticing journey through pet healthcare, exploring intriguing guinea pig diseases, practical strategies for cat-friendly clinics, and interactive ophthalmology cases. Deep-dive into neurological emergencies through dynamic case videos. Discover rabbit urinary tract diseases, decode the behaviour of confrontational cats, understand the rising trend of ocular disease in brachycephalic dogs, and tackle the challenge of spinal pain in young dogs.

A compelling exploration tailored for vets from anywhere in the world, primed to spark your curiosity and reignite your passion for animal care.

''Also known as: Virtual Congress, VC24, VVC24, and Virtual Congress 2024.''

[https://thewebinarvet.com/events/virtual-veterinary-congress-2024?utm_source=wikivet&utm_medium=referral&utm_campaign=homepage '''Register for FREE today!''']

[[File:Start Your 7-Day Free Trial.jpg|alt=The Webinar Vet Free Trial|left|thumb]]

== Access 2,500 Veterinary CE Videos | Start Your 7-Day Risk Free Trial ==

Introducing The Webinar Vet, the groundbreaking CE platform that's revolutionizing the veterinary industry! Are you looking to maintain your CE progress effortlessly? The Webinar Vet has got your back. Seeking an easy way to download your CE certificates? Absolutely, that's covered too.

The Webinar Vet offers webinars and podcasts that are not just informative but also compatible across various devices. Whether you're on a tablet, smartphone, or computer, you can start watching on one device and continue seamlessly on another, ensuring you never miss a critical detail during transitions.

There's more to discover! The Webinar Vet's webinars are enriched with detailed synopses, release notes, and some even include interactive Q&A sessions. This ensures you gain the most from your CE experience. With new webinars and podcasts introduced weekly by leading experts, you're guaranteed a continuous stream of up-to-date veterinary knowledge.

[https://thewebinarvet.com/memberships?utm_source=wikivet&utm_medium=referral&utm_campaign=homepage '''Start Your 7-Day Free Trial Today!''']

[[File:VetChat Logo.png|left|alt=|thumb]]
==VETchat Podcast==
Looking for on-the-go content on all things veterinary? VETchat by The Webinar Vet brings you exclusive discussions with members all across the veterinary profession. From hot topical debates to mini CPD/CE lessons, we cover just about everything! Join us weekly to learn, be inspired, and be entertained.
[https://thewebinarvet.com/videos/category/podcast?utm_source=wikivet&utm_medium=referral&utm_campaign=homepage '''Listen to all episodes''']

</div>

[[es:Página Principal]]
[[fr:Accueil]]

Veterinary Education Online

2023-12-18T12:23:13Z

Roytwv:

__NOTOC__
<templatestyles src="Main Page/styles.css" />
<div id="mp-topbanner" class="mp-bordered">
<div id="mp-welcomecount">
<div id="mp-welcome">Welcome to [[Main Page|WikiVet]],</div>
<div id="mp-free">Free [[WikiVet Introduction|veterinary encyclopedia]]. [[Frequently_Asked_Questions#How_do_I_edit_content|Submissions welcome]]<br>and are reviewed by renowned veterinary professionals.</div>
<div id="articlecount">[[Special:Statistics|{{NUMBEROFARTICLES}}]] articles in English</div>
</div>
<ul id="mp-portals">
<li>[[CPD Events]]</li>
<li class="portal-vmid">[[Discipline]]s</li>
<li class="portal-vbot">[[Learning Resources|Learning]]</li>
<li class="portal-hmid">[[Lectures]]</li>
<li class="portal-hmid portal-vmid">[[Podcasts]]</li>
<li class="portal-hmid portal-vbot">[[Species]]</li>
<li class="portal-hright">[[System]]</li>
<li class="portal-hright portal-vmid">[https://www.thewebinarvet.com/?utm_source=wikivet&utm_medium=webinar_hp_link Webinars]</li>
<li class="portal-hright portal-vbot">[[Video]]s</li>
</ul>
</div>

<div class="MainPageBG" style="border:1px solid #5B9DA7; background:#f5faff; color:#000; padding:0 14px 8px; margin-top:7px;">[[File:Vvc24-wiki.jpg|alt=Virtual Veterinary Conference 2024|left|thumb|300x300px]]

== Register for FREE: Virtual Veterinary Conference 2024 ==

Embark on an enticing journey through pet healthcare, exploring intriguing guinea pig diseases, practical strategies for cat-friendly clinics, and interactive ophthalmology cases. Deep-dive into neurological emergencies through dynamic case videos. Discover rabbit urinary tract diseases, decode the behaviour of confrontational cats, understand the rising trend of ocular disease in brachycephalic dogs, and tackle the challenge of spinal pain in young dogs.

A compelling exploration tailored for vets from anywhere in the world, primed to spark your curiosity and reignite your passion for animal care.

''Also known as: Virtual Congress, VC24, VVC24, and Virtual Congress 2024.''

[https://thewebinarvet.com/events/virtual-veterinary-congress-2024?utm_source=wikivet&utm_medium=referral&utm_campaign=homepage '''Register for FREE today!''']

[[File:Start Your 7-Day Free Trial.jpg|alt=The Webinar Vet Free Trial|left|thumb]]

== Access 2,500 Veterinary CE Videos | Start Your 7-Day Risk Free Trial ==

Introducing The Webinar Vet, the groundbreaking CE platform that's revolutionizing the veterinary industry! Are you looking to maintain your CE progress effortlessly? The Webinar Vet has got your back. Seeking an easy way to download your CE certificates? Absolutely, that's covered too.

The Webinar Vet offers webinars and podcasts that are not just informative but also compatible across various devices. Whether you're on a tablet, smartphone, or computer, you can start watching on one device and continue seamlessly on another, ensuring you never miss a critical detail during transitions.

There's more to discover! The Webinar Vet's webinars are enriched with detailed synopses, release notes, and some even include interactive Q&A sessions. This ensures you gain the most from your CE experience. With new webinars and podcasts introduced weekly by leading experts, you're guaranteed a continuous stream of up-to-date veterinary knowledge.

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[[File:VetChat Logo.png|left|alt=|thumb]]
==VETchat Podcast==
Looking for on-the-go content on all things veterinary? VETchat by The Webinar Vet brings you exclusive discussions with members all across the veterinary profession. From hot topical debates to mini CPD/CE lessons, we cover just about everything! Join us weekly to learn, be inspired, and be entertained.
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Veterinary Education Online

2023-12-18T12:22:08Z

Roytwv: Homepage update

__NOTOC__
<templatestyles src="Main Page/styles.css" />
<div id="mp-topbanner" class="mp-bordered">
<div id="mp-welcomecount">
<div id="mp-welcome">Welcome to [[Main Page|WikiVet]],</div>
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</div>
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<li>[[CPD Events]]</li>
<li class="portal-vmid">[[Discipline]]s</li>
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== Register for FREE: Virtual Veterinary Conference 2024 ==

Embark on an enticing journey through pet healthcare, exploring intriguing guinea pig diseases, practical strategies for cat-friendly clinics, and interactive ophthalmology cases. Deep-dive into neurological emergencies through dynamic case videos. Discover rabbit urinary tract diseases, decode the behaviour of confrontational cats, understand the rising trend of ocular disease in brachycephalic dogs, and tackle the challenge of spinal pain in young dogs.

A compelling exploration tailored for vets from anywhere in the world, primed to spark your curiosity and reignite your passion for animal care.

''Also known as: Virtual Congress, VC24, VVC24, and Virtual Congress 2024.''

[https://thewebinarvet.com/events/virtual-veterinary-congress-2024?utm_source=wikivet&utm_medium=referral&utm_campaign=homepage '''Register for FREE today!''']

[[File:Start Your 7-Day Free Trial.jpg|alt=The Webinar Vet Free Trial|left|thumb]]

== Access 2,500 Veterinary CE Videos | Start Your 7-Day Risk Free Trial ==

Introducing The Webinar Vet, the groundbreaking CE platform that's revolutionizing the veterinary industry! Are you looking to maintain your CE progress effortlessly? The Webinar Vet has got your back. Seeking an easy way to download your CE certificates? Absolutely, that's covered too.

The Webinar Vet offers webinars and podcasts that are not just informative but also compatible across various devices. Whether you're on a tablet, smartphone, or computer, you can start watching on one device and continue seamlessly on another, ensuring you never miss a critical detail during transitions.

There's more to discover! The Webinar Vet's webinars are enriched with detailed synopses, release notes, and some even include interactive Q&A sessions. This ensures you gain the most from your CE experience. With new webinars and podcasts introduced weekly by leading experts, you're guaranteed a continuous stream of up-to-date veterinary knowledge.

[https://thewebinarvet.com/memberships?utm_source=wikivet&utm_medium=referral&utm_campaign=homepage '''Start Your 7-Day Free Trial Today!''']

[[File:VetChat Logo.png|left|alt=|thumb]]
==VETchat Podcast==
Looking for on-the-go content on all things veterinary? VETchat by The Webinar Vet brings you exclusive discussions with members all across the veterinary profession. From hot topical debates to mini CPD/CE lessons, we cover just about everything! Join us weekly to learn, be inspired, and be entertained.
[https://thewebinarvet.com/videos/category/podcast?utm_source=wikivet&utm_medium=referral&utm_campaign=homepage '''Listen to all episodes''']

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File:Start Your 7-Day Free Trial.jpg

2023-12-18T12:19:55Z

Roytwv:

The Webinar Vet Free Trial

File:Vvc24-wiki.jpg

2023-12-18T12:02:34Z

Roytwv:

Virtual Veterinary Conference 2024

CPD Events

2023-08-29T07:42:59Z

Roytwv:

== Virtual Events brought to you by The Webinar Vet ==
We are proud to help the veterinary community access CPD/CE conferences and events online from all over the world.

All of the following events are available to view online, either live, or as webinar recordings you can view at your own convenience.

=== '''[https://thewebinarvet.com/events/virtual-veterinary-congress-2024?utm_source=wikivet&utm_medium=referral&utm_campaign=vc2024 Virtual Congress 2024]''' ===
Embark on an enticing journey through pet healthcare, exploring intriguing guinea pig diseases, practical strategies for cat-friendly clinics, and interactive ophthalmology cases. Deep-dive into neurological emergencies through dynamic case videos. Discover rabbit urinary tract diseases, decode the behaviour of confrontational cats, understand the rising trend of ocular disease in brachycephalic dogs, and tackle the challenge of spinal pain in young dogs.

A compelling exploration tailored for vets from anywhere in the world, primed to spark your curiosity and reignite your passion for animal care.

[https://www.thewebinarvet.com/pages/save-the-date-virtual-congress-2022/?utm_source=wikivet&utm_medium=referral&utm_campaign=vc2022 Save Your Seat]

Vetstream

2023-06-13T10:34:40Z

Roytwv: Changed redirect target from Https://en.wikivet.net/ to Veterinary Education Online

#REDIRECT [[Veterinary Education Online]]
#REDIRECT [[Https://en.wikivet.net/]]'''FREE''' access to Vetstream for all WikiVet '''registered student users'''. Select from '''[[Canis]], [[Felis]], [[Equis]] or [[Lapis]]''' content.
<br><br>
[[File:Vetlexicon advert button.png|right|350px|link=https://en.wikivet.net/Vetstream]]

[[File:Canis-title-logo.gif|left|75px|link=https://en.wikivet.net/Canis]]<br><br>

[[File:Felis-title-logo.gif|left|75px|link=https://en.wikivet.net/Felis]]<br><br>

[[File:Equis-title-logo.gif|left|75px|link=https://en.wikivet.net/Equis]]<br><br>

[[File:Lapis-title-logo.gif|left|75px|link=https://en.wikivet.net/Lapis]]<br><br>
----

'''Free Student Access'''

WikiVet student users can now access '''[https://www.vetstream.com/home?u=wikivetstudent Vetstream]''' free of charge. This provides students with a major new clinical educational and reference resource which will be invaluable to veterinary studies as well as clinical practice.

'''Recent Graduate Subsidised Rates'''

For recent graduates, we have also secured a special deal so that existing WikiVet users will get a reduction in subscription rates. Graduates in their first year of practice will get a 66% discount whilst second year graduates get a 33% discount.

'''Institutional Access'''
Veterinary schools who sign up for an institutional licence also stand to benefit - of importance to WikiVet is the fact that institutions from developing nations will benefit from preferential terms in line with their economic development. Please contact Vetstream directly for information about your school can benefit from an institutional licence.

'''More Information'''

Finally, it is important to note that access to WikiVet content will remain completely free. However, we do receive a commission for users who decide to register with Vetstream So we hope that you find that free access to Vetstream is useful to you and that when you graduate you will be encouraged to subscribe and help subsidise access to WikiVet for future generations of students.

Visit '''[[Vetstream Information]]''' for more information about the partnership between Vetstream and WikiVet.

[[Category:Delete]]
__NOINDEX__

Vetstream

2023-06-13T10:33:01Z

Roytwv: Changed redirect target from / to Https://en.wikivet.net/

#REDIRECT [[Https://en.wikivet.net/]]'''FREE''' access to Vetstream for all WikiVet '''registered student users'''. Select from '''[[Canis]], [[Felis]], [[Equis]] or [[Lapis]]''' content.
<br><br>
[[File:Vetlexicon advert button.png|right|350px|link=https://en.wikivet.net/Vetstream]]

[[File:Canis-title-logo.gif|left|75px|link=https://en.wikivet.net/Canis]]<br><br>

[[File:Felis-title-logo.gif|left|75px|link=https://en.wikivet.net/Felis]]<br><br>

[[File:Equis-title-logo.gif|left|75px|link=https://en.wikivet.net/Equis]]<br><br>

[[File:Lapis-title-logo.gif|left|75px|link=https://en.wikivet.net/Lapis]]<br><br>
----

'''Free Student Access'''

WikiVet student users can now access '''[https://www.vetstream.com/home?u=wikivetstudent Vetstream]''' free of charge. This provides students with a major new clinical educational and reference resource which will be invaluable to veterinary studies as well as clinical practice.

'''Recent Graduate Subsidised Rates'''

For recent graduates, we have also secured a special deal so that existing WikiVet users will get a reduction in subscription rates. Graduates in their first year of practice will get a 66% discount whilst second year graduates get a 33% discount.

'''Institutional Access'''
Veterinary schools who sign up for an institutional licence also stand to benefit - of importance to WikiVet is the fact that institutions from developing nations will benefit from preferential terms in line with their economic development. Please contact Vetstream directly for information about your school can benefit from an institutional licence.

'''More Information'''

Finally, it is important to note that access to WikiVet content will remain completely free. However, we do receive a commission for users who decide to register with Vetstream So we hope that you find that free access to Vetstream is useful to you and that when you graduate you will be encouraged to subscribe and help subsidise access to WikiVet for future generations of students.

Visit '''[[Vetstream Information]]''' for more information about the partnership between Vetstream and WikiVet.

[[Category:Delete]]
__NOINDEX__

Vetstream

2023-06-13T10:32:19Z

Roytwv: redirect to HP

#REDIRECT [[/]]'''FREE''' access to Vetstream for all WikiVet '''registered student users'''. Select from '''[[Canis]], [[Felis]], [[Equis]] or [[Lapis]]''' content.
<br><br>
[[File:Vetlexicon advert button.png|right|350px|link=https://en.wikivet.net/Vetstream]]

[[File:Canis-title-logo.gif|left|75px|link=https://en.wikivet.net/Canis]]<br><br>

[[File:Felis-title-logo.gif|left|75px|link=https://en.wikivet.net/Felis]]<br><br>

[[File:Equis-title-logo.gif|left|75px|link=https://en.wikivet.net/Equis]]<br><br>

[[File:Lapis-title-logo.gif|left|75px|link=https://en.wikivet.net/Lapis]]<br><br>
----

'''Free Student Access'''

WikiVet student users can now access '''[https://www.vetstream.com/home?u=wikivetstudent Vetstream]''' free of charge. This provides students with a major new clinical educational and reference resource which will be invaluable to veterinary studies as well as clinical practice.

'''Recent Graduate Subsidised Rates'''

For recent graduates, we have also secured a special deal so that existing WikiVet users will get a reduction in subscription rates. Graduates in their first year of practice will get a 66% discount whilst second year graduates get a 33% discount.

'''Institutional Access'''
Veterinary schools who sign up for an institutional licence also stand to benefit - of importance to WikiVet is the fact that institutions from developing nations will benefit from preferential terms in line with their economic development. Please contact Vetstream directly for information about your school can benefit from an institutional licence.

'''More Information'''

Finally, it is important to note that access to WikiVet content will remain completely free. However, we do receive a commission for users who decide to register with Vetstream So we hope that you find that free access to Vetstream is useful to you and that when you graduate you will be encouraged to subscribe and help subsidise access to WikiVet for future generations of students.

Visit '''[[Vetstream Information]]''' for more information about the partnership between Vetstream and WikiVet.

[[Category:Delete]]
__NOINDEX__

Vetstream

2023-06-13T10:30:19Z

Roytwv: Protected "Vetstream" ([Edit=Allow only administrators] (indefinite) [Move=Allow only administrators] (indefinite))

'''FREE''' access to Vetstream for all WikiVet '''registered student users'''. Select from '''[[Canis]], [[Felis]], [[Equis]] or [[Lapis]]''' content.
<br><br>
[[File:Vetlexicon advert button.png|right|350px|link=https://en.wikivet.net/Vetstream]]

[[File:Canis-title-logo.gif|left|75px|link=https://en.wikivet.net/Canis]]<br><br>

[[File:Felis-title-logo.gif|left|75px|link=https://en.wikivet.net/Felis]]<br><br>

[[File:Equis-title-logo.gif|left|75px|link=https://en.wikivet.net/Equis]]<br><br>

[[File:Lapis-title-logo.gif|left|75px|link=https://en.wikivet.net/Lapis]]<br><br>
----

'''Free Student Access'''

WikiVet student users can now access '''[https://www.vetstream.com/home?u=wikivetstudent Vetstream]''' free of charge. This provides students with a major new clinical educational and reference resource which will be invaluable to veterinary studies as well as clinical practice.

'''Recent Graduate Subsidised Rates'''

For recent graduates, we have also secured a special deal so that existing WikiVet users will get a reduction in subscription rates. Graduates in their first year of practice will get a 66% discount whilst second year graduates get a 33% discount.

'''Institutional Access'''
Veterinary schools who sign up for an institutional licence also stand to benefit - of importance to WikiVet is the fact that institutions from developing nations will benefit from preferential terms in line with their economic development. Please contact Vetstream directly for information about your school can benefit from an institutional licence.

'''More Information'''

Finally, it is important to note that access to WikiVet content will remain completely free. However, we do receive a commission for users who decide to register with Vetstream So we hope that you find that free access to Vetstream is useful to you and that when you graduate you will be encouraged to subscribe and help subsidise access to WikiVet for future generations of students.

Visit '''[[Vetstream Information]]''' for more information about the partnership between Vetstream and WikiVet.

[[Category:Delete]]

Rumen - Anatomy & Physiology

2022-11-02T14:05:54Z

Roytwv:

{{OpenPagesTop}}
[[Image:Rumen Topography Sheep.jpg|thumb|right|250px|Rumen Topography (Sheep) - Copyright RVC 2008]]

==Introduction==

The rumen is the first chamber of the ruminant stomach. It is the largest chamber and has regular contractions to move food around for digestion, eliminate gases through [[Eructation|eructation]] and send food particles back to the mouth for [[Mastication|remastication]]. The rumen breaks down food particles through mechanical digestion and fermentation with the help of symbiotic microbes. [[Volatile Fatty Acids|Volatile fatty acids]] are the main product of ruminant digestion.

==Structure==

[[Image:Rumen Anatomy Sheep.jpg|thumb|right|250px|Rumen Anatomy (Sheep) - Copyright RVC 2008]]
Grooves correspond with thickened smooth muscle pillars on the inside of the rumen. '''Ruminal pillars''' divide the dorsal and ventral ruminal sacs. '''Coronary pillars''' divide the caudal blind sacs. The '''cranial pillar''' divides the dorsal and cranial sacs. It is covered by the greater omentum. The rumen is 38-40°C, anaerobic and has a pH of 6.7. It is buffered and has a large holding capacity. Water intake lowers the ruminal temperature so bacteria are tolerant to temperature changes towards the lower end of the scale. Objects are often lodged in the rumino-reticular fold. When the rumen contracts, the object can be pushed through the [[Reticulum - Anatomy & Physiology|reticulum]] wall into the [[Heart Structure - Anatomy & Physiology#Pericardium|pericardium]] and [[Heart - Anatomy & Physiology|heart]].

The rumen is laterally compressed and extends from the cardia at the level of the 8th rib to the pelvic inlet. The serosa covers the entire rumen except dorsally where the rumen attaches to the abdominal roof allowing more freedom for ruminal movement and expansion. Ruminal contractions can be felt for in the left paralumbar fossa. 1-2 contractions should be felt per minute. The opening at the cardia into both the rumen and [[Reticulum - Anatomy & Physiology|reticulum]] is called the reticular groove (see [[Oesophageal Groove|oesophageal groove]]).

==Function==

The rumen is involved in waste removal. Simpler products of digestion are assimilated directly, others continue down the digestive tract for further digestion. It mixes food and moves it forwards through the stomach chambers. Sensors in the rumen can determine the coarseness of the food. Coarse, tough feed needs stronger and more frequent ruminal contractions. The '''vagus nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN X]]) is needed for control of stomach movements. The reflex control is through sensory receptors in the medulla.

See [[Rumination|rumination]] and [[Eructation|eructation]].

==Ruminoreticular contraction==

[[Image:Contractions of the ruminoreticulum diagram.jpg|thumb|right|250px|Diagram of the contractions of the ruminoreticulum - Copyright RVC 2008]]

The contractions have two main functions:
:Primary contraction mixes food by a ruminoreticuluar mixing cycle. There are 2 contractions of the reticulum (2nd most powerful) which continue over the [[Rumen - Anatomy & Physiology|rumen]]. Ingesta flows from the reticulum to cranial rumenal sac and then to reticulum (or ventral sac). It occurs every 60 seconds.

:The secondary contraction lets gas out (see [[Eructation|eructation]]). Ingesta flows from the ventral blind sac to the dorsal blind sac then to dorsal sac (eructation) and to the ventral sac.

==Vasculature==

The rumen receives blood from the '''celiac artery''' which branches into the '''right''' and '''left ruminal arteries'''.

==Innervation==

The rumen is innervated by the '''dorsal vagus''' nerve ([[Cranial Nerves - Anatomy & Physiology|CN X]]) (most important) and '''ventral vagus''' ([[Cranial Nerves - Anatomy & Physiology|CN X]]) nerve.

==Lymphatics==

The caudal '''mediastinal lymph node''' enlargement puts pressure on the dorsal vagus effecting ruminal contractions. There are numerous small lymph nodes scattered in the ruminal grooves. The lymph drains to larger atrial nodes between the cardia and the [[Omasum - Anatomy & Physiology|omasum]], then to the cistera chyli.

==Rumen Microbes==

The rumen has a variety of microbes that can utilise many substrates. The dominance of different bacterial species depends on pH. Ergo, microbial populations are not constant. Microbes digest cellulose and hemi-cellulose and provide a source of all amino acids. Microbes also synthesise vitamins (especially the B vitamins).

==Rumen Microbial Population==

'''Bacteria'''
There are over 2000 species, 99.5% are obligate anaerobes.

'''Protozoa'''
Large, unicellular organisms that prey on bacteria. Numbers are affected by diet.

'''Fungi'''
Digest fibre. Numbers present are usually low.

'''Common Rumen Microbes'''
{| style="width:75%; height:200px" border="1"

!'''Species'''
!'''Type'''
!'''pH'''
|-
| '''''Ruminococcus flavefauens'''''
| Fibre
| 6.15
|-
| '''''Fibrobacter succinogens'''''
| Fibre
| 6
|-
| '''''Megashpaera eisdeni'''''
| Lactate user
| 4.9
|-
| '''''Streptococcus bovis'''''
| Lactate producer
| 4.55
|}

==Histology==

[[Image:Rumen Histology Sheep.jpg|thumb|right|250px|Rumen Histology (Sheep) - Copyright RVC 2008]]
The rumen has a '''keratinised stratified squamous epithelium'''. It is non-glandular and has no '''lamina muscularis'''.

There are two thick layers of '''tunica muscularis''', the inner circular and the outer longitudinal. The interior surface of the rumen forms numerous papillae. The papillae can be long and foliated or short and pointed. They are up to 6mm in length. Animals fed on rough grass or in the dry season have longer papillae, whereas animals fed on digestible feed or in the wet season have shorter papillae (1-2mm in length). There are fewer papillae present dorsally. They increase the surface area for [[Volatile Fatty Acids|volatile fatty acid]] absorption. The upper keratinised layer of papillae also protects the rumen against abrasion. The deeper layers of papillae metabolise the [[Volatile Fatty Acids|volatile fatty acids]].

==Species Differences==

===Small Ruminants===

Sheep and goats have a larger ventral ruminal sac than dorsal ruminal sac. The cranial mesenteric artery and celiac artery come off the same root.

===Bovine===

The cranial mesenteric artery and celiac artery are close in the cow. Dairy cows have a rumen pH of 5.5 due to more digestible feed.
<br />
<br />

==Links==

'''Click here for information on [[Reticulum - Anatomy & Physiology|the Reticulum - Anatomy & Physiology]]'''

'''Click here for information on [[Omasum - Anatomy & Physiology|the Omasum - Anatomy & Physiology]]'''

'''Click here for information on [[Abomasum - Anatomy & Physiology|the Abomasum- Anatomy & Physiology]]'''
<br><br>
{{Learning
|flashcards = [[Rumen Flashcards]]
|videos = [http://stream2.rvc.ac.uk/Anatomy/bovine/Pot0052.mp4 Lateral view of the Abdomen of a young Ruminant]<br>[http://stream2.rvc.ac.uk/Anatomy/bovine/pot0175.mp4 Sections of the Ruminant Stomach]<br>[http://stream2.rvc.ac.uk/Frean/sheep/LeftSideTopography.mp4 Left sided topography of the Ovine Abdomen and Thorax]<br>[http://stream2.rvc.ac.uk/Frean/sheep/RightSideTopography.mp4 Right sided topography of the Ovine Abdomen]<br>[http://stream2.rvc.ac.uk/Frean/sheep/RuminantStomachStructure.mp4 Structure of the ruminant forestomachs]
|OVAM = [http://www.onlineveterinaryanatomy.net/content/sheep-rumen-external-aspect Sheep Rumen (external aspect)]
}}

==Webinars==
<rss max="10" filterout="nutrition" highlight="cattle cow cows">https://www.thewebinarvet.com/gastroenterology-and-nutrition/webinars/feed</rss>

[[Category:Stomach - Anatomy & Physiology]]
[[Category:A&P Done]]
[[Category:Alimentary Anatomy - Cattle]]

Rumen - Anatomy & Physiology

2022-11-02T14:04:16Z

Roytwv:

{{OpenPagesTop}}
[[Image:Rumen Topography Sheep.jpg|thumb|right|250px|Rumen Topography (Sheep) - Copyright RVC 2008]]

==Introduction==

The rumen is the first chamber of the ruminant stomach. It is the largest chamber and has regular contractions to move food around for digestion, eliminate gases through [[Eructation|eructation]] and send food particles back to the mouth for [[Mastication|remastication]]. The rumen breaks down food particles through mechanical digestion and fermentation with the help of symbiotic microbes. [[Volatile Fatty Acids|Volatile fatty acids]] are the main product of ruminant digestion.

==Structure==

[[Image:Rumen Anatomy Sheep.jpg|thumb|right|250px|Rumen Anatomy (Sheep) - Copyright RVC 2008]]
Grooves correspond with thickened smooth muscle pillars on the inside of the rumen. '''Ruminal pillars''' divide the dorsal and ventral ruminal sacs. '''Coronary pillars''' divide the caudal blind sacs. The '''cranial pillar''' divides the dorsal and cranial sacs. It is covered by the greater omentum. The rumen is 38-40°C, anaerobic and has a pH of 6.7. It is buffered and has a large holding capacity. Water intake lowers the ruminal temperature so bacteria are tolerant to temperature changes towards the lower end of the scale. Objects are often lodged in the rumino-reticular fold. When the rumen contracts, the object can be pushed through the [[Reticulum - Anatomy & Physiology|reticulum]] wall into the [[Heart Structure - Anatomy & Physiology#Pericardium|pericardium]] and [[Heart - Anatomy & Physiology|heart]].

The rumen is laterally compressed and extends from the cardia at the level of the 8th rib to the pelvic inlet. The serosa covers the entire rumen except dorsally where the rumen attaches to the abdominal roof allowing more freedom for ruminal movement and expansion. Ruminal contractions can be felt for in the left paralumbar fossa. 1-2 contractions should be felt per minute. The opening at the cardia into both the rumen and [[Reticulum - Anatomy & Physiology|reticulum]] is called the reticular groove (see [[Oesophageal Groove|oesophageal groove]]).

==Function==

The rumen is involved in waste removal. Simpler products of digestion are assimilated directly, others continue down the digestive tract for further digestion. It mixes food and moves it forwards through the stomach chambers. Sensors in the rumen can determine the coarseness of the food. Coarse, tough feed needs stronger and more frequent ruminal contractions. The '''vagus nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN X]]) is needed for control of stomach movements. The reflex control is through sensory receptors in the medulla.

See [[Rumination|rumination]] and [[Eructation|eructation]].

==Ruminoreticular contraction==

[[Image:Contractions of the ruminoreticulum diagram.jpg|thumb|right|250px|Diagram of the contractions of the ruminoreticulum - Copyright RVC 2008]]

The contractions have two main functions:
:Primary contraction mixes food by a ruminoreticuluar mixing cycle. There are 2 contractions of the reticulum (2nd most powerful) which continue over the [[Rumen - Anatomy & Physiology|rumen]]. Ingesta flows from the reticulum to cranial rumenal sac and then to reticulum (or ventral sac). It occurs every 60 seconds.

:The secondary contraction lets gas out (see [[Eructation|eructation]]). Ingesta flows from the ventral blind sac to the dorsal blind sac then to dorsal sac (eructation) and to the ventral sac.

==Vasculature==

The rumen receives blood from the '''celiac artery''' which branches into the '''right''' and '''left ruminal arteries'''.

==Innervation==

The rumen is innervated by the '''dorsal vagus''' nerve ([[Cranial Nerves - Anatomy & Physiology|CN X]]) (most important) and '''ventral vagus''' ([[Cranial Nerves - Anatomy & Physiology|CN X]]) nerve.

==Lymphatics==

The caudal '''mediastinal lymph node''' enlargement puts pressure on the dorsal vagus effecting ruminal contractions. There are numerous small lymph nodes scattered in the ruminal grooves. The lymph drains to larger atrial nodes between the cardia and the [[Omasum - Anatomy & Physiology|omasum]], then to the cistera chyli.

==Rumen Microbes==

The rumen has a variety of microbes that can utilise many substrates. The dominance of different bacterial species depends on pH. Ergo, microbial populations are not constant. Microbes digest cellulose and hemi-cellulose and provide a source of all amino acids. Microbes also synthesise vitamins (especially the B vitamins).

==Rumen Microbial Population==

'''Bacteria'''
There are over 2000 species, 99.5% are obligate anaerobes.

'''Protozoa'''
Large, unicellular organisms that prey on bacteria. Numbers are affected by diet.

'''Fungi'''
Digest fibre. Numbers present are usually low.

'''Common Rumen Microbes'''
{| style="width:75%; height:200px" border="1"

!'''Species'''
!'''Type'''
!'''pH'''
|-
| '''''Ruminococcus flavefauens'''''
| Fibre
| 6.15
|-
| '''''Fibrobacter succinogens'''''
| Fibre
| 6
|-
| '''''Megashpaera eisdeni'''''
| Lactate user
| 4.9
|-
| '''''Streptococcus bovis'''''
| Lactate producer
| 4.55
|}

==Histology==

[[Image:Rumen Histology Sheep.jpg|thumb|right|250px|Rumen Histology (Sheep) - Copyright RVC 2008]]
The rumen has a '''keratinised stratified squamous epithelium'''. It is non-glandular and has no '''lamina muscularis'''.

There are two thick layers of '''tunica muscularis''', the inner circular and the outer longitudinal. The interior surface of the rumen forms numerous papillae. The papillae can be long and foliated or short and pointed. They are up to 6mm in length. Animals fed on rough grass or in the dry season have longer papillae, whereas animals fed on digestible feed or in the wet season have shorter papillae (1-2mm in length). There are fewer papillae present dorsally. They increase the surface area for [[Volatile Fatty Acids|volatile fatty acid]] absorption. The upper keratinised layer of papillae also protects the rumen against abrasion. The deeper layers of papillae metabolise the [[Volatile Fatty Acids|volatile fatty acids]].

==Species Differences==

===Small Ruminants===

Sheep and goats have a larger ventral ruminal sac than dorsal ruminal sac. The cranial mesenteric artery and celiac artery come off the same root.

===Bovine===

The cranial mesenteric artery and celiac artery are close in the cow. Dairy cows have a rumen pH of 5.5 due to more digestible feed.
<br />
<br />

==Links==

'''Click here for information on [[Reticulum - Anatomy & Physiology|the Reticulum - Anatomy & Physiology]]'''

'''Click here for information on [[Omasum - Anatomy & Physiology|the Omasum - Anatomy & Physiology]]'''

'''Click here for information on [[Abomasum - Anatomy & Physiology|the Abomasum- Anatomy & Physiology]]'''
<br><br>
{{Learning
|flashcards = [[Rumen Flashcards]]
|videos = [http://stream2.rvc.ac.uk/Anatomy/bovine/Pot0052.mp4 Lateral view of the Abdomen of a young Ruminant]<br>[http://stream2.rvc.ac.uk/Anatomy/bovine/pot0175.mp4 Sections of the Ruminant Stomach]<br>[http://stream2.rvc.ac.uk/Frean/sheep/LeftSideTopography.mp4 Left sided topography of the Ovine Abdomen and Thorax]<br>[http://stream2.rvc.ac.uk/Frean/sheep/RightSideTopography.mp4 Right sided topography of the Ovine Abdomen]<br>[http://stream2.rvc.ac.uk/Frean/sheep/RuminantStomachStructure.mp4 Structure of the ruminant forestomachs]
|OVAM = [http://www.onlineveterinaryanatomy.net/content/sheep-rumen-external-aspect Sheep Rumen (external aspect)]
}}

==Webinars==
<rss max="10" highlight="cattle cow cows">https://www.thewebinarvet.com/gastroenterology-and-nutrition/webinars/feed</rss>

[[Category:Stomach - Anatomy & Physiology]]
[[Category:A&P Done]]
[[Category:Alimentary Anatomy - Cattle]]

Rumen - Anatomy & Physiology

2022-11-02T13:58:11Z

Roytwv:

{{OpenPagesTop}}
[[Image:Rumen Topography Sheep.jpg|thumb|right|250px|Rumen Topography (Sheep) - Copyright RVC 2008]]

==Introduction==

The rumen is the first chamber of the ruminant stomach. It is the largest chamber and has regular contractions to move food around for digestion, eliminate gases through [[Eructation|eructation]] and send food particles back to the mouth for [[Mastication|remastication]]. The rumen breaks down food particles through mechanical digestion and fermentation with the help of symbiotic microbes. [[Volatile Fatty Acids|Volatile fatty acids]] are the main product of ruminant digestion.

==Structure==

[[Image:Rumen Anatomy Sheep.jpg|thumb|right|250px|Rumen Anatomy (Sheep) - Copyright RVC 2008]]
Grooves correspond with thickened smooth muscle pillars on the inside of the rumen. '''Ruminal pillars''' divide the dorsal and ventral ruminal sacs. '''Coronary pillars''' divide the caudal blind sacs. The '''cranial pillar''' divides the dorsal and cranial sacs. It is covered by the greater omentum. The rumen is 38-40°C, anaerobic and has a pH of 6.7. It is buffered and has a large holding capacity. Water intake lowers the ruminal temperature so bacteria are tolerant to temperature changes towards the lower end of the scale. Objects are often lodged in the rumino-reticular fold. When the rumen contracts, the object can be pushed through the [[Reticulum - Anatomy & Physiology|reticulum]] wall into the [[Heart Structure - Anatomy & Physiology#Pericardium|pericardium]] and [[Heart - Anatomy & Physiology|heart]].

The rumen is laterally compressed and extends from the cardia at the level of the 8th rib to the pelvic inlet. The serosa covers the entire rumen except dorsally where the rumen attaches to the abdominal roof allowing more freedom for ruminal movement and expansion. Ruminal contractions can be felt for in the left paralumbar fossa. 1-2 contractions should be felt per minute. The opening at the cardia into both the rumen and [[Reticulum - Anatomy & Physiology|reticulum]] is called the reticular groove (see [[Oesophageal Groove|oesophageal groove]]).

==Function==

The rumen is involved in waste removal. Simpler products of digestion are assimilated directly, others continue down the digestive tract for further digestion. It mixes food and moves it forwards through the stomach chambers. Sensors in the rumen can determine the coarseness of the food. Coarse, tough feed needs stronger and more frequent ruminal contractions. The '''vagus nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN X]]) is needed for control of stomach movements. The reflex control is through sensory receptors in the medulla.

See [[Rumination|rumination]] and [[Eructation|eructation]].

==Ruminoreticular contraction==

[[Image:Contractions of the ruminoreticulum diagram.jpg|thumb|right|250px|Diagram of the contractions of the ruminoreticulum - Copyright RVC 2008]]

The contractions have two main functions:
:Primary contraction mixes food by a ruminoreticuluar mixing cycle. There are 2 contractions of the reticulum (2nd most powerful) which continue over the [[Rumen - Anatomy & Physiology|rumen]]. Ingesta flows from the reticulum to cranial rumenal sac and then to reticulum (or ventral sac). It occurs every 60 seconds.

:The secondary contraction lets gas out (see [[Eructation|eructation]]). Ingesta flows from the ventral blind sac to the dorsal blind sac then to dorsal sac (eructation) and to the ventral sac.

==Vasculature==

The rumen receives blood from the '''celiac artery''' which branches into the '''right''' and '''left ruminal arteries'''.

==Innervation==

The rumen is innervated by the '''dorsal vagus''' nerve ([[Cranial Nerves - Anatomy & Physiology|CN X]]) (most important) and '''ventral vagus''' ([[Cranial Nerves - Anatomy & Physiology|CN X]]) nerve.

==Lymphatics==

The caudal '''mediastinal lymph node''' enlargement puts pressure on the dorsal vagus effecting ruminal contractions. There are numerous small lymph nodes scattered in the ruminal grooves. The lymph drains to larger atrial nodes between the cardia and the [[Omasum - Anatomy & Physiology|omasum]], then to the cistera chyli.

==Rumen Microbes==

The rumen has a variety of microbes that can utilise many substrates. The dominance of different bacterial species depends on pH. Ergo, microbial populations are not constant. Microbes digest cellulose and hemi-cellulose and provide a source of all amino acids. Microbes also synthesise vitamins (especially the B vitamins).

==Rumen Microbial Population==

'''Bacteria'''
There are over 2000 species, 99.5% are obligate anaerobes.

'''Protozoa'''
Large, unicellular organisms that prey on bacteria. Numbers are affected by diet.

'''Fungi'''
Digest fibre. Numbers present are usually low.

'''Common Rumen Microbes'''
{| style="width:75%; height:200px" border="1"

!'''Species'''
!'''Type'''
!'''pH'''
|-
| '''''Ruminococcus flavefauens'''''
| Fibre
| 6.15
|-
| '''''Fibrobacter succinogens'''''
| Fibre
| 6
|-
| '''''Megashpaera eisdeni'''''
| Lactate user
| 4.9
|-
| '''''Streptococcus bovis'''''
| Lactate producer
| 4.55
|}

==Histology==

[[Image:Rumen Histology Sheep.jpg|thumb|right|250px|Rumen Histology (Sheep) - Copyright RVC 2008]]
The rumen has a '''keratinised stratified squamous epithelium'''. It is non-glandular and has no '''lamina muscularis'''.

There are two thick layers of '''tunica muscularis''', the inner circular and the outer longitudinal. The interior surface of the rumen forms numerous papillae. The papillae can be long and foliated or short and pointed. They are up to 6mm in length. Animals fed on rough grass or in the dry season have longer papillae, whereas animals fed on digestible feed or in the wet season have shorter papillae (1-2mm in length). There are fewer papillae present dorsally. They increase the surface area for [[Volatile Fatty Acids|volatile fatty acid]] absorption. The upper keratinised layer of papillae also protects the rumen against abrasion. The deeper layers of papillae metabolise the [[Volatile Fatty Acids|volatile fatty acids]].

==Species Differences==

===Small Ruminants===

Sheep and goats have a larger ventral ruminal sac than dorsal ruminal sac. The cranial mesenteric artery and celiac artery come off the same root.

===Bovine===

The cranial mesenteric artery and celiac artery are close in the cow. Dairy cows have a rumen pH of 5.5 due to more digestible feed.
<br />
<br />

==Links==

'''Click here for information on [[Reticulum - Anatomy & Physiology|the Reticulum - Anatomy & Physiology]]'''

'''Click here for information on [[Omasum - Anatomy & Physiology|the Omasum - Anatomy & Physiology]]'''

'''Click here for information on [[Abomasum - Anatomy & Physiology|the Abomasum- Anatomy & Physiology]]'''
<br><br>
{{Learning
|flashcards = [[Rumen Flashcards]]
|videos = [http://stream2.rvc.ac.uk/Anatomy/bovine/Pot0052.mp4 Lateral view of the Abdomen of a young Ruminant]<br>[http://stream2.rvc.ac.uk/Anatomy/bovine/pot0175.mp4 Sections of the Ruminant Stomach]<br>[http://stream2.rvc.ac.uk/Frean/sheep/LeftSideTopography.mp4 Left sided topography of the Ovine Abdomen and Thorax]<br>[http://stream2.rvc.ac.uk/Frean/sheep/RightSideTopography.mp4 Right sided topography of the Ovine Abdomen]<br>[http://stream2.rvc.ac.uk/Frean/sheep/RuminantStomachStructure.mp4 Structure of the ruminant forestomachs]
|OVAM = [http://www.onlineveterinaryanatomy.net/content/sheep-rumen-external-aspect Sheep Rumen (external aspect)]
}}

==Webinars==
<rss max="10" highlight="none">https://www.thewebinarvet.com/gastroenterology-and-nutrition/webinars/feed</rss>

[[Category:Stomach - Anatomy & Physiology]]
[[Category:A&P Done]]
[[Category:Alimentary Anatomy - Cattle]]

Rumen - Anatomy & Physiology

2022-11-02T13:57:37Z

Roytwv:

{{OpenPagesTop}}
[[Image:Rumen Topography Sheep.jpg|thumb|right|250px|Rumen Topography (Sheep) - Copyright RVC 2008]]

==Introduction==

The rumen is the first chamber of the ruminant stomach. It is the largest chamber and has regular contractions to move food around for digestion, eliminate gases through [[Eructation|eructation]] and send food particles back to the mouth for [[Mastication|remastication]]. The rumen breaks down food particles through mechanical digestion and fermentation with the help of symbiotic microbes. [[Volatile Fatty Acids|Volatile fatty acids]] are the main product of ruminant digestion.

==Structure==

[[Image:Rumen Anatomy Sheep.jpg|thumb|right|250px|Rumen Anatomy (Sheep) - Copyright RVC 2008]]
Grooves correspond with thickened smooth muscle pillars on the inside of the rumen. '''Ruminal pillars''' divide the dorsal and ventral ruminal sacs. '''Coronary pillars''' divide the caudal blind sacs. The '''cranial pillar''' divides the dorsal and cranial sacs. It is covered by the greater omentum. The rumen is 38-40°C, anaerobic and has a pH of 6.7. It is buffered and has a large holding capacity. Water intake lowers the ruminal temperature so bacteria are tolerant to temperature changes towards the lower end of the scale. Objects are often lodged in the rumino-reticular fold. When the rumen contracts, the object can be pushed through the [[Reticulum - Anatomy & Physiology|reticulum]] wall into the [[Heart Structure - Anatomy & Physiology#Pericardium|pericardium]] and [[Heart - Anatomy & Physiology|heart]].

The rumen is laterally compressed and extends from the cardia at the level of the 8th rib to the pelvic inlet. The serosa covers the entire rumen except dorsally where the rumen attaches to the abdominal roof allowing more freedom for ruminal movement and expansion. Ruminal contractions can be felt for in the left paralumbar fossa. 1-2 contractions should be felt per minute. The opening at the cardia into both the rumen and [[Reticulum - Anatomy & Physiology|reticulum]] is called the reticular groove (see [[Oesophageal Groove|oesophageal groove]]).

==Function==

The rumen is involved in waste removal. Simpler products of digestion are assimilated directly, others continue down the digestive tract for further digestion. It mixes food and moves it forwards through the stomach chambers. Sensors in the rumen can determine the coarseness of the food. Coarse, tough feed needs stronger and more frequent ruminal contractions. The '''vagus nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN X]]) is needed for control of stomach movements. The reflex control is through sensory receptors in the medulla.

See [[Rumination|rumination]] and [[Eructation|eructation]].

==Ruminoreticular contraction==

[[Image:Contractions of the ruminoreticulum diagram.jpg|thumb|right|250px|Diagram of the contractions of the ruminoreticulum - Copyright RVC 2008]]

The contractions have two main functions:
:Primary contraction mixes food by a ruminoreticuluar mixing cycle. There are 2 contractions of the reticulum (2nd most powerful) which continue over the [[Rumen - Anatomy & Physiology|rumen]]. Ingesta flows from the reticulum to cranial rumenal sac and then to reticulum (or ventral sac). It occurs every 60 seconds.

:The secondary contraction lets gas out (see [[Eructation|eructation]]). Ingesta flows from the ventral blind sac to the dorsal blind sac then to dorsal sac (eructation) and to the ventral sac.

==Vasculature==

The rumen receives blood from the '''celiac artery''' which branches into the '''right''' and '''left ruminal arteries'''.

==Innervation==

The rumen is innervated by the '''dorsal vagus''' nerve ([[Cranial Nerves - Anatomy & Physiology|CN X]]) (most important) and '''ventral vagus''' ([[Cranial Nerves - Anatomy & Physiology|CN X]]) nerve.

==Lymphatics==

The caudal '''mediastinal lymph node''' enlargement puts pressure on the dorsal vagus effecting ruminal contractions. There are numerous small lymph nodes scattered in the ruminal grooves. The lymph drains to larger atrial nodes between the cardia and the [[Omasum - Anatomy & Physiology|omasum]], then to the cistera chyli.

==Rumen Microbes==

The rumen has a variety of microbes that can utilise many substrates. The dominance of different bacterial species depends on pH. Ergo, microbial populations are not constant. Microbes digest cellulose and hemi-cellulose and provide a source of all amino acids. Microbes also synthesise vitamins (especially the B vitamins).

==Rumen Microbial Population==

'''Bacteria'''
There are over 2000 species, 99.5% are obligate anaerobes.

'''Protozoa'''
Large, unicellular organisms that prey on bacteria. Numbers are affected by diet.

'''Fungi'''
Digest fibre. Numbers present are usually low.

'''Common Rumen Microbes'''
{| style="width:75%; height:200px" border="1"

!'''Species'''
!'''Type'''
!'''pH'''
|-
| '''''Ruminococcus flavefauens'''''
| Fibre
| 6.15
|-
| '''''Fibrobacter succinogens'''''
| Fibre
| 6
|-
| '''''Megashpaera eisdeni'''''
| Lactate user
| 4.9
|-
| '''''Streptococcus bovis'''''
| Lactate producer
| 4.55
|}

==Histology==

[[Image:Rumen Histology Sheep.jpg|thumb|right|250px|Rumen Histology (Sheep) - Copyright RVC 2008]]
The rumen has a '''keratinised stratified squamous epithelium'''. It is non-glandular and has no '''lamina muscularis'''.

There are two thick layers of '''tunica muscularis''', the inner circular and the outer longitudinal. The interior surface of the rumen forms numerous papillae. The papillae can be long and foliated or short and pointed. They are up to 6mm in length. Animals fed on rough grass or in the dry season have longer papillae, whereas animals fed on digestible feed or in the wet season have shorter papillae (1-2mm in length). There are fewer papillae present dorsally. They increase the surface area for [[Volatile Fatty Acids|volatile fatty acid]] absorption. The upper keratinised layer of papillae also protects the rumen against abrasion. The deeper layers of papillae metabolise the [[Volatile Fatty Acids|volatile fatty acids]].

==Species Differences==

===Small Ruminants===

Sheep and goats have a larger ventral ruminal sac than dorsal ruminal sac. The cranial mesenteric artery and celiac artery come off the same root.

===Bovine===

The cranial mesenteric artery and celiac artery are close in the cow. Dairy cows have a rumen pH of 5.5 due to more digestible feed.
<br />
<br />

==Links==

'''Click here for information on [[Reticulum - Anatomy & Physiology|the Reticulum - Anatomy & Physiology]]'''

'''Click here for information on [[Omasum - Anatomy & Physiology|the Omasum - Anatomy & Physiology]]'''

'''Click here for information on [[Abomasum - Anatomy & Physiology|the Abomasum- Anatomy & Physiology]]'''
<br><br>
{{Learning
|flashcards = [[Rumen Flashcards]]
|videos = [http://stream2.rvc.ac.uk/Anatomy/bovine/Pot0052.mp4 Lateral view of the Abdomen of a young Ruminant]<br>[http://stream2.rvc.ac.uk/Anatomy/bovine/pot0175.mp4 Sections of the Ruminant Stomach]<br>[http://stream2.rvc.ac.uk/Frean/sheep/LeftSideTopography.mp4 Left sided topography of the Ovine Abdomen and Thorax]<br>[http://stream2.rvc.ac.uk/Frean/sheep/RightSideTopography.mp4 Right sided topography of the Ovine Abdomen]<br>[http://stream2.rvc.ac.uk/Frean/sheep/RuminantStomachStructure.mp4 Structure of the ruminant forestomachs]
|OVAM = [http://www.onlineveterinaryanatomy.net/content/sheep-rumen-external-aspect Sheep Rumen (external aspect)]
}}

==Webinars==
<rss max="10" filterout="" highlight="none">https://www.thewebinarvet.com/gastroenterology-and-nutrition/webinars/feed</rss>

[[Category:Stomach - Anatomy & Physiology]]
[[Category:A&P Done]]
[[Category:Alimentary Anatomy - Cattle]]

Rumen - Anatomy & Physiology

2022-11-02T13:56:18Z

Roytwv:

{{OpenPagesTop}}
[[Image:Rumen Topography Sheep.jpg|thumb|right|250px|Rumen Topography (Sheep) - Copyright RVC 2008]]

==Introduction==

The rumen is the first chamber of the ruminant stomach. It is the largest chamber and has regular contractions to move food around for digestion, eliminate gases through [[Eructation|eructation]] and send food particles back to the mouth for [[Mastication|remastication]]. The rumen breaks down food particles through mechanical digestion and fermentation with the help of symbiotic microbes. [[Volatile Fatty Acids|Volatile fatty acids]] are the main product of ruminant digestion.

==Structure==

[[Image:Rumen Anatomy Sheep.jpg|thumb|right|250px|Rumen Anatomy (Sheep) - Copyright RVC 2008]]
Grooves correspond with thickened smooth muscle pillars on the inside of the rumen. '''Ruminal pillars''' divide the dorsal and ventral ruminal sacs. '''Coronary pillars''' divide the caudal blind sacs. The '''cranial pillar''' divides the dorsal and cranial sacs. It is covered by the greater omentum. The rumen is 38-40°C, anaerobic and has a pH of 6.7. It is buffered and has a large holding capacity. Water intake lowers the ruminal temperature so bacteria are tolerant to temperature changes towards the lower end of the scale. Objects are often lodged in the rumino-reticular fold. When the rumen contracts, the object can be pushed through the [[Reticulum - Anatomy & Physiology|reticulum]] wall into the [[Heart Structure - Anatomy & Physiology#Pericardium|pericardium]] and [[Heart - Anatomy & Physiology|heart]].

The rumen is laterally compressed and extends from the cardia at the level of the 8th rib to the pelvic inlet. The serosa covers the entire rumen except dorsally where the rumen attaches to the abdominal roof allowing more freedom for ruminal movement and expansion. Ruminal contractions can be felt for in the left paralumbar fossa. 1-2 contractions should be felt per minute. The opening at the cardia into both the rumen and [[Reticulum - Anatomy & Physiology|reticulum]] is called the reticular groove (see [[Oesophageal Groove|oesophageal groove]]).

==Function==

The rumen is involved in waste removal. Simpler products of digestion are assimilated directly, others continue down the digestive tract for further digestion. It mixes food and moves it forwards through the stomach chambers. Sensors in the rumen can determine the coarseness of the food. Coarse, tough feed needs stronger and more frequent ruminal contractions. The '''vagus nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN X]]) is needed for control of stomach movements. The reflex control is through sensory receptors in the medulla.

See [[Rumination|rumination]] and [[Eructation|eructation]].

==Ruminoreticular contraction==

[[Image:Contractions of the ruminoreticulum diagram.jpg|thumb|right|250px|Diagram of the contractions of the ruminoreticulum - Copyright RVC 2008]]

The contractions have two main functions:
:Primary contraction mixes food by a ruminoreticuluar mixing cycle. There are 2 contractions of the reticulum (2nd most powerful) which continue over the [[Rumen - Anatomy & Physiology|rumen]]. Ingesta flows from the reticulum to cranial rumenal sac and then to reticulum (or ventral sac). It occurs every 60 seconds.

:The secondary contraction lets gas out (see [[Eructation|eructation]]). Ingesta flows from the ventral blind sac to the dorsal blind sac then to dorsal sac (eructation) and to the ventral sac.

==Vasculature==

The rumen receives blood from the '''celiac artery''' which branches into the '''right''' and '''left ruminal arteries'''.

==Innervation==

The rumen is innervated by the '''dorsal vagus''' nerve ([[Cranial Nerves - Anatomy & Physiology|CN X]]) (most important) and '''ventral vagus''' ([[Cranial Nerves - Anatomy & Physiology|CN X]]) nerve.

==Lymphatics==

The caudal '''mediastinal lymph node''' enlargement puts pressure on the dorsal vagus effecting ruminal contractions. There are numerous small lymph nodes scattered in the ruminal grooves. The lymph drains to larger atrial nodes between the cardia and the [[Omasum - Anatomy & Physiology|omasum]], then to the cistera chyli.

==Rumen Microbes==

The rumen has a variety of microbes that can utilise many substrates. The dominance of different bacterial species depends on pH. Ergo, microbial populations are not constant. Microbes digest cellulose and hemi-cellulose and provide a source of all amino acids. Microbes also synthesise vitamins (especially the B vitamins).

==Rumen Microbial Population==

'''Bacteria'''
There are over 2000 species, 99.5% are obligate anaerobes.

'''Protozoa'''
Large, unicellular organisms that prey on bacteria. Numbers are affected by diet.

'''Fungi'''
Digest fibre. Numbers present are usually low.

'''Common Rumen Microbes'''
{| style="width:75%; height:200px" border="1"

!'''Species'''
!'''Type'''
!'''pH'''
|-
| '''''Ruminococcus flavefauens'''''
| Fibre
| 6.15
|-
| '''''Fibrobacter succinogens'''''
| Fibre
| 6
|-
| '''''Megashpaera eisdeni'''''
| Lactate user
| 4.9
|-
| '''''Streptococcus bovis'''''
| Lactate producer
| 4.55
|}

==Histology==

[[Image:Rumen Histology Sheep.jpg|thumb|right|250px|Rumen Histology (Sheep) - Copyright RVC 2008]]
The rumen has a '''keratinised stratified squamous epithelium'''. It is non-glandular and has no '''lamina muscularis'''.

There are two thick layers of '''tunica muscularis''', the inner circular and the outer longitudinal. The interior surface of the rumen forms numerous papillae. The papillae can be long and foliated or short and pointed. They are up to 6mm in length. Animals fed on rough grass or in the dry season have longer papillae, whereas animals fed on digestible feed or in the wet season have shorter papillae (1-2mm in length). There are fewer papillae present dorsally. They increase the surface area for [[Volatile Fatty Acids|volatile fatty acid]] absorption. The upper keratinised layer of papillae also protects the rumen against abrasion. The deeper layers of papillae metabolise the [[Volatile Fatty Acids|volatile fatty acids]].

==Species Differences==

===Small Ruminants===

Sheep and goats have a larger ventral ruminal sac than dorsal ruminal sac. The cranial mesenteric artery and celiac artery come off the same root.

===Bovine===

The cranial mesenteric artery and celiac artery are close in the cow. Dairy cows have a rumen pH of 5.5 due to more digestible feed.
<br />
<br />

==Links==

'''Click here for information on [[Reticulum - Anatomy & Physiology|the Reticulum - Anatomy & Physiology]]'''

'''Click here for information on [[Omasum - Anatomy & Physiology|the Omasum - Anatomy & Physiology]]'''

'''Click here for information on [[Abomasum - Anatomy & Physiology|the Abomasum- Anatomy & Physiology]]'''
<br><br>
{{Learning
|flashcards = [[Rumen Flashcards]]
|videos = [http://stream2.rvc.ac.uk/Anatomy/bovine/Pot0052.mp4 Lateral view of the Abdomen of a young Ruminant]<br>[http://stream2.rvc.ac.uk/Anatomy/bovine/pot0175.mp4 Sections of the Ruminant Stomach]<br>[http://stream2.rvc.ac.uk/Frean/sheep/LeftSideTopography.mp4 Left sided topography of the Ovine Abdomen and Thorax]<br>[http://stream2.rvc.ac.uk/Frean/sheep/RightSideTopography.mp4 Right sided topography of the Ovine Abdomen]<br>[http://stream2.rvc.ac.uk/Frean/sheep/RuminantStomachStructure.mp4 Structure of the ruminant forestomachs]
|OVAM = [http://www.onlineveterinaryanatomy.net/content/sheep-rumen-external-aspect Sheep Rumen (external aspect)]
}}

==Webinars==
<rss max="10" highlight="none">https://www.thewebinarvet.com/gastroenterology-and-nutrition/webinars/feed</rss>

[[Category:Stomach - Anatomy & Physiology]]
[[Category:A&P Done]]
[[Category:Alimentary Anatomy - Cattle]]

Reticulum - Anatomy & Physiology

2022-10-27T19:45:14Z

Roytwv:

{{OpenPagesTop}}
==Introduction==

The reticulum is the second chamber of the ruminant stomach. It has regular contractions which precede the biphasic ruminal contraction for digestion of food particles. Mechanical digestion and microbial fermentation occur to breakdown food particles for absorption. [[Volatile Fatty Acids|Volatile fatty acids]] are the major product of ruminant digestion.

==Structure==

[[Image:Reticulum Anatomy Sheep.jpg|thumb|right|250px|Reticulum Anatomy (Sheep) - Copyright RVC 2008]]

The reticulum is covered by greater omentum. The rumino-reticular fold often gets objects lodged. When the [[Rumen - Anatomy & Physiology|rumen]] contracts, the object can be pushed through the reticulum wall into the [[Heart Structure - Anatomy & Physiology#Pericardium|pericardium]] and [[Heart - Anatomy & Physiology|heart]].

Opening at the cardia into both the reticulum and the [[Rumen - Anatomy & Physiology|rumen]] is called the reticular groove (see [[Oesophageal Groove|oseophageal groove]]). The reticular groove also opens into the [[Omasum - Anatomy & Physiology|omasum]].

The reticulum is cranial to the [[Rumen - Anatomy & Physiology|rumen]] at ribs 6-8. It is located from cardia to the diaphragm. It lies above the xiphoid process of the sternum. Serosa covers the surface.

==Function==

The functions of the reticulum include waste removal and movement. Simpler products of digestion are assimilated directly, others continue down the digestive tract for further digestion.

See [[Rumination|rumination]] and [[Eructation|eructation]].

==Ruminoreticular contraction==

[[Image:Contractions of the ruminoreticulum diagram.jpg|thumb|right|250px|Diagram of the contractions of the ruminoreticulum - Copyright RVC 2008]]

The contractions have two main functions:
:Primary contraction mixes food by a ruminoreticuluar mixing cycle. There are 2 contractions of the reticulum (2nd most powerful) which continue over the [[Rumen - Anatomy & Physiology|rumen]]. Ingesta flows from the reticulum to cranial rumenal sac and then to reticulum (or ventral sac). It occurs every 60 seconds.

:The secondary contraction lets gas out (see [[Eructation|eructation]]). Ingesta flows from the ventral blind sac to the dorsal blind sac then to dorsal sac (eructation) and to the ventral sac.

==Vasculature==

The reticulum receives blood supply from the '''cranial mesenteric artery''', '''celiac artery''' and '''right and left ruminal arteries'''.

==Innervation==

The reticulum is innervated by the '''dorsal vagus''' ([[Cranial Nerves - Anatomy & Physiology|CN X]]) (most important) and the '''ventral vagus''' nerve ([[Cranial Nerves - Anatomy & Physiology|CN X]]).

==Lymphatics==

Numerous small lymph nodes are scattered in the grooves. The lymph drains to larger atrial nodes between the cardia and [[Omasum - Anatomy & Physiology|omasum]], then to the cistera chyli.

==Histology==

[[Image:Reticulum Histology Sheep.jpg|thumb|right|250px|Reticulum Histology (Sheep) - Copyright RVC 2008]]
The reticulum is lined by a '''keratinised stratified squamous epithelium''' and there are no glands present. The characteristic honeycomb appearance is formed by the mucosal layer trown into short and tall folds. The folds gradually merge into '''papillae''', where the reticulum meets the rumen. [[Tongue - Anatomy & Physiology#Types of Papillae|Conical papillae]], also called secondary papillae, are present on folds, providing a rough surface to increase food breakdown.

The '''lamina muscularis''' is present as discrete bands of smooth muscle (not continuous). There are two thick layers of '''tunica muscularis''', the inner circular and the outer longitudinal. The upper keratinised layer of the reticulum protects against abrasion and the deeper layers metabolise [[Volatile Fatty Acids|volatile fatty acids]].

==Species Differences==

===Small Ruminants===

Small ruminants have a larger reticulum compared to cattle. In sheep and goats, the ridges of the reticular cells are lower and have more prominent serrated edges than in cattle. The papillated ruminal mucosa expands over a greater proportion of the reticulum.
<br />
<br />

==Links==

'''Click here for information on [[Rumen - Anatomy & Physiology|Rumen]]'''

'''Click here for information on [[Omasum - Anatomy & Physiology|Omasum]]'''

'''Click here for information on [[Abomasum - Anatomy & Physiology|Abomasum]]'''

{{Template:Learning
|flashcards = [[Reticulum Flashcards]]
}}

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[[Category:Stomach - Anatomy & Physiology]]
[[Category:A&P Done]]
[[Category:Alimentary Anatomy - Cattle]]

Reticulum - Anatomy & Physiology

2022-10-27T19:44:36Z

Roytwv:

{{OpenPagesTop}}
==Introduction==

The reticulum is the second chamber of the ruminant stomach. It has regular contractions which precede the biphasic ruminal contraction for digestion of food particles. Mechanical digestion and microbial fermentation occur to breakdown food particles for absorption. [[Volatile Fatty Acids|Volatile fatty acids]] are the major product of ruminant digestion.

==Structure==

[[Image:Reticulum Anatomy Sheep.jpg|thumb|right|250px|Reticulum Anatomy (Sheep) - Copyright RVC 2008]]

The reticulum is covered by greater omentum. The rumino-reticular fold often gets objects lodged. When the [[Rumen - Anatomy & Physiology|rumen]] contracts, the object can be pushed through the reticulum wall into the [[Heart Structure - Anatomy & Physiology#Pericardium|pericardium]] and [[Heart - Anatomy & Physiology|heart]].

Opening at the cardia into both the reticulum and the [[Rumen - Anatomy & Physiology|rumen]] is called the reticular groove (see [[Oesophageal Groove|oseophageal groove]]). The reticular groove also opens into the [[Omasum - Anatomy & Physiology|omasum]].

The reticulum is cranial to the [[Rumen - Anatomy & Physiology|rumen]] at ribs 6-8. It is located from cardia to the diaphragm. It lies above the xiphoid process of the sternum. Serosa covers the surface.

==Function==

The functions of the reticulum include waste removal and movement. Simpler products of digestion are assimilated directly, others continue down the digestive tract for further digestion.

See [[Rumination|rumination]] and [[Eructation|eructation]].

==Ruminoreticular contraction==

[[Image:Contractions of the ruminoreticulum diagram.jpg|thumb|right|250px|Diagram of the contractions of the ruminoreticulum - Copyright RVC 2008]]

The contractions have two main functions:
:Primary contraction mixes food by a ruminoreticuluar mixing cycle. There are 2 contractions of the reticulum (2nd most powerful) which continue over the [[Rumen - Anatomy & Physiology|rumen]]. Ingesta flows from the reticulum to cranial rumenal sac and then to reticulum (or ventral sac). It occurs every 60 seconds.

:The secondary contraction lets gas out (see [[Eructation|eructation]]). Ingesta flows from the ventral blind sac to the dorsal blind sac then to dorsal sac (eructation) and to the ventral sac.

==Vasculature==

The reticulum receives blood supply from the '''cranial mesenteric artery''', '''celiac artery''' and '''right and left ruminal arteries'''.

==Innervation==

The reticulum is innervated by the '''dorsal vagus''' ([[Cranial Nerves - Anatomy & Physiology|CN X]]) (most important) and the '''ventral vagus''' nerve ([[Cranial Nerves - Anatomy & Physiology|CN X]]).

==Lymphatics==

Numerous small lymph nodes are scattered in the grooves. The lymph drains to larger atrial nodes between the cardia and [[Omasum - Anatomy & Physiology|omasum]], then to the cistera chyli.

==Histology==

[[Image:Reticulum Histology Sheep.jpg|thumb|right|250px|Reticulum Histology (Sheep) - Copyright RVC 2008]]
The reticulum is lined by a '''keratinised stratified squamous epithelium''' and there are no glands present. The characteristic honeycomb appearance is formed by the mucosal layer trown into short and tall folds. The folds gradually merge into '''papillae''', where the reticulum meets the rumen. [[Tongue - Anatomy & Physiology#Types of Papillae|Conical papillae]], also called secondary papillae, are present on folds, providing a rough surface to increase food breakdown.

The '''lamina muscularis''' is present as discrete bands of smooth muscle (not continuous). There are two thick layers of '''tunica muscularis''', the inner circular and the outer longitudinal. The upper keratinised layer of the reticulum protects against abrasion and the deeper layers metabolise [[Volatile Fatty Acids|volatile fatty acids]].

==Species Differences==

===Small Ruminants===

Small ruminants have a larger reticulum compared to cattle. In sheep and goats, the ridges of the reticular cells are lower and have more prominent serrated edges than in cattle. The papillated ruminal mucosa expands over a greater proportion of the reticulum.
<br />
<br />

==Links==

'''Click here for information on [[Rumen - Anatomy & Physiology|Rumen]]'''

'''Click here for information on [[Omasum - Anatomy & Physiology|Omasum]]'''

'''Click here for information on [[Abomasum - Anatomy & Physiology|Abomasum]]'''

{{Template:Learning
|flashcards = [[Reticulum Flashcards]]
}}

==Webinars==
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[[Category:Stomach - Anatomy & Physiology]]
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[[Category:Alimentary Anatomy - Cattle]]

Central Nervous System - Histology

2022-10-27T19:43:50Z

Roytwv:

{{OpenPagesTop}}
==Introduction==
The Central Nervous System (CNS) is composed of the brain and the spinal cord. This page is specifically focussed on the histologic appearance, for anatomy see [[Forebrain - Anatomy & Physiology|Forebrain]], [[Midbrain - Anatomy & Physiology|Midbrain]], [[Hindbrain - Anatomy & Physiology|Hindbrain]], [[Cranial Nerves - Anatomy & Physiology|Cranial Nerves]], [[Spinal Cord - Anatomy & Physiology|Spinal Cord]] and [[CNS Development - Anatomy & Physiology|CNS Development]].

==Spinal Cord==
The spinal cord is composed of two discrete parts; the [[Spinal Cord - Anatomy & Physiology#White_Matter|white matter]], which is the outer part of the cord and the [[Spinal Cord - Anatomy & Physiology#Grey_Matter|grey matter]], which is the inner portion of the cord. The white matter is given this name due to its appearance in unfixed histological specimens in which the white nature of the tissue is caused by the myelination of ascending and descending [[Neurons - Anatomy & Physiology|nerve fibres]]. The grey matter is also named after its unfixed histological appearance and contains the cell bodies of neurons as well as nerve fibres.
<br />
<br />
Within the spinal cord the grey matter forms an H-shape where the ventral horns of the H are broader than the dorsal horns. The grey matter shape has also been likened to that of a butterfly. The grey matter also has a histologically visible central canal running through it. The ventral horns of the grey matter contain the cell bodies of motor neurones whilst the dorsal horns contain sensory neurons where the cell bodies are found in the dorsal root ganglia. Please see [[Spinal Cord - Anatomy & Physiology#Sensory_Pathways|sensory pathways]] for further information on the composition of nerve fibres within the spinal cord.

The relative size of the grey matter is dependant on the number of motor cells related to controlling limbs and therefore the size varies along the length of the spine. Around the areas of the fore and hindlimbs, the grey matter is considerably larger.
[[Image:WIKIVETspinalcord1.jpg|thumb|centre|350px|Spinal Cord - © John Bredl]]
<br />
The above image shows a complete cross-sectional histology of a spinal cord. In this particular stain (H&E) the grey matter can be seen in a slightly darker shade than the white matter. The relative size of the grey matter is small compared to the white matter and therefore the level of the cross-section is unlikely to be around the level of any limbs. The dorsal horns can be seen to extend near to the dorso-lateral surface of the spine. The slide also contains small elements of the dorsal and ventral roots leaving the spinal cord. The connecting element of the grey matter which is immediately ventral to the central canal is called the '''grey commissure''' (GC). The stained areas found around the edge of the spinal cord are fibrous material that is the pia mater. This pia mater follows the contours of the spinal cord and also folds into the ventral fissure. At the ventral aspect of the ventral fissure some small blood vessels can be seen present in the pia mater.
<br />
[[Image:WIKIVETspinalcord2.jpg|thumb|centre|350px|Spinal Cord 2 - © John Bredl]]
<br />
The above image shows a higher magnification view of the grey matter of the spinal cord which is clearly surrounded by white matter. The ventral horn has a number of processes which extend into the white mater. The image displays a number of multipolar cells that are relatively large compared to the nerve fibres which surround these cells. Although at this magnification it is not possible to definitively identify these cells but it is likely that they are cell bodies of neurons. The surrounding nerve fibres are likely to be neuroglial cells, although the cytoplasm of these cells is not visible. The seemingly poor organisation of the tissues surrounding these neurons is often referred to as '''neuropil'''.
<br />
[[Image:WIKIVETspinalcord3.jpg|thumb|centre|350px|Spinal Cord 3 - © John Bredl]]
<br />
This image shows a further magnified view which displays the central canal and [[Ependymal Cells|ependymal cell]] layers. The surrounding tissue is similar to that of the grey matter neuropil seen in the previous image above. Within the central canal vessel some remnants of [[Cerebral Spinal Fluid - Anatomy & Physiology|CSF]] can be seen. Within the neuropil tissues, some cell bodies can be seen.

===Rabbit Spinal Cord===
<br />
[[File:Rabbitspinalcord40x.jpg|thumb|centre|350px|Rabbit Spinalcord at 40x Magnification]]
<br />
This image shows a moderately magnified image of the outer edge of the spinal cord. The bulk of the histological appearance is made up by white matter which is predominantly nerve fibres and myelin sheaths. This histological image clearly shows the different layering of protection around the outside of the spinal cord and how closely associated this protection is. The outer layer is the [[Meninges - Anatomy & Physiology#Dura_mater|dura mater]] and then continuing to move towards the spinal cord there is the [[Meninges - Anatomy & Physiology#Subdural_space|sub-dural space]] leading to the [[Meninges - Anatomy & Physiology#Arachnoid mater|arachnoid mater]]. Inside the arachnoid space is the [[Meninges - Anatomy & Physiology#Subarachnoid Space|sub-arachnoid space]] and then the [[Meninges - Anatomy & Physiology#Pia Mater|pia mater]] which is closely bound to the underlying neural tissues.

==Brain==
===Cerebrum section===
The [[Forebrain - Anatomy & Physiology|cerebrum]] contains the cell bodies of nerves both receiving and sending sensory information involved in controlling voluntary movement via motor activity and in the integration and coordination of other nerves. The cerebrum is also involved in memory functions.
<br />
<br />
In a full thickness histological image of the cerebrum it would be possible to distinguish numerous layers including the pia mater on the outer edge of the brain, the plexiform layer, pyramidal layer, granular layer and a polymorphic cell layer innermost, prior to the white matter towards the centre of the brain. The plexiform layer consists of mainly fibrous material which run in parallel to the surface of the brain. This layer contains relatively few cells, mainly neuroglial cells. The pyramidal cell layers mainly consist of small, medium and large pyramidal shaped cells which generally become larger as they become closer to the white matter of the cerebrum. Finally the pleomorphic layer contains cells of very diverse shapes, a majority of which have a spindle shape. These cells are often called fusiform cells.
[[Image:WIKIVETcerebrum.jpg|thumb|centre|350px|Cerebrum - © John Bredl]]
<br />
The histologic image above displays a very clear high magnification image of cell bodies with dendrites and axons extending from them. It should be noted that such a clear image of the nerve cells with their associated nerve fibres within the cerebrum is unusual and in most cases at a magnification of 350x a more detailed view of the types of cells found in the layers described above would be seen. A common stain for the cerebrum is Luxol blue which allows the visualisation of the plexiform cells, small to large pyramidal cells, granular cells and pleopmorphic cells. In most cases small capillaries are also usually visible, although none are present on the image above. Surrounding the neurons is the neuropil which is made up of densely packed aggregation of nerve fibres and neuroglial cells.

===Cerebellum section===
The [[Hindbrain - Anatomy & Physiology#Cerebellum|cerebellum]] lies behind the brain and below the level of the cerebrum. The cerebellum coordinates voluntary movements via controlling multiple muscle function as well as maintaining normal posture.
[[File:Cerebellum.jpg|thumb|centre|350px|Cerebellum]]
<br />
Although the above image is of a relatively poor quality, it is useful in displaying the general histologic appearance of the cerebellum. This cerebellum has been stained with haematoxylin and eosin (H&E) and shows the outermost '''molecular layer''' and the inner '''granular layer'''. The molecular layer stains more intensely with eosin whilst the granular layer stains more intensely with haematoxylin. Both of these layers make up the cortex of the cerebellum. Although not visible on this image, the granular layer contains a further, deeper area that stains less intensely with haematoxylin. This lighter central contains the white matter. In this image there is a moderate degree of detachment of the molecular layer from the granular layer which is due to the histology fixing process rather than the true physiological appearance.

On the outer edge of the molecular layer it is possible to visualise the pia mater fibrous covering. In the above image and as is common in cerebellar histology, the fixing process causes shrinkage of the pia mater resulting in an artefact appearance.
[[Image:WIKIVETcerebellum.jpg|thumb|centre|350px|Cerebellum - © John Bredl]]
<br />
This image shows a higher magnification of the junction between the molecular and granular layer. This junction contains a number of large cell bodies which are called '''Purkinje cells'''. Purkinje cells are characteristic of the histologic appearance of the cerebellum. Each cell has a number of dendrites that are within the molecular layer. The granular layer has a slightly darker mottled appearance which is made up of small neurons called '''Granule cells'''. These cells receive impulses from other parts of the CNS.

{{Template:Learning
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}}

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[[Category:Nervous System - Anatomy & Physiology]][[Category:Histology]]
[[Category:A&P Done]]

Central Nervous System - Histology

2022-10-27T19:43:32Z

Roytwv:

{{OpenPagesTop}}
==Introduction==
The Central Nervous System (CNS) is composed of the brain and the spinal cord. This page is specifically focussed on the histologic appearance, for anatomy see [[Forebrain - Anatomy & Physiology|Forebrain]], [[Midbrain - Anatomy & Physiology|Midbrain]], [[Hindbrain - Anatomy & Physiology|Hindbrain]], [[Cranial Nerves - Anatomy & Physiology|Cranial Nerves]], [[Spinal Cord - Anatomy & Physiology|Spinal Cord]] and [[CNS Development - Anatomy & Physiology|CNS Development]].

==Spinal Cord==
The spinal cord is composed of two discrete parts; the [[Spinal Cord - Anatomy & Physiology#White_Matter|white matter]], which is the outer part of the cord and the [[Spinal Cord - Anatomy & Physiology#Grey_Matter|grey matter]], which is the inner portion of the cord. The white matter is given this name due to its appearance in unfixed histological specimens in which the white nature of the tissue is caused by the myelination of ascending and descending [[Neurons - Anatomy & Physiology|nerve fibres]]. The grey matter is also named after its unfixed histological appearance and contains the cell bodies of neurons as well as nerve fibres.
<br />
<br />
Within the spinal cord the grey matter forms an H-shape where the ventral horns of the H are broader than the dorsal horns. The grey matter shape has also been likened to that of a butterfly. The grey matter also has a histologically visible central canal running through it. The ventral horns of the grey matter contain the cell bodies of motor neurones whilst the dorsal horns contain sensory neurons where the cell bodies are found in the dorsal root ganglia. Please see [[Spinal Cord - Anatomy & Physiology#Sensory_Pathways|sensory pathways]] for further information on the composition of nerve fibres within the spinal cord.

The relative size of the grey matter is dependant on the number of motor cells related to controlling limbs and therefore the size varies along the length of the spine. Around the areas of the fore and hindlimbs, the grey matter is considerably larger.
[[Image:WIKIVETspinalcord1.jpg|thumb|centre|350px|Spinal Cord - © John Bredl]]
<br />
The above image shows a complete cross-sectional histology of a spinal cord. In this particular stain (H&E) the grey matter can be seen in a slightly darker shade than the white matter. The relative size of the grey matter is small compared to the white matter and therefore the level of the cross-section is unlikely to be around the level of any limbs. The dorsal horns can be seen to extend near to the dorso-lateral surface of the spine. The slide also contains small elements of the dorsal and ventral roots leaving the spinal cord. The connecting element of the grey matter which is immediately ventral to the central canal is called the '''grey commissure''' (GC). The stained areas found around the edge of the spinal cord are fibrous material that is the pia mater. This pia mater follows the contours of the spinal cord and also folds into the ventral fissure. At the ventral aspect of the ventral fissure some small blood vessels can be seen present in the pia mater.
<br />
[[Image:WIKIVETspinalcord2.jpg|thumb|centre|350px|Spinal Cord 2 - © John Bredl]]
<br />
The above image shows a higher magnification view of the grey matter of the spinal cord which is clearly surrounded by white matter. The ventral horn has a number of processes which extend into the white mater. The image displays a number of multipolar cells that are relatively large compared to the nerve fibres which surround these cells. Although at this magnification it is not possible to definitively identify these cells but it is likely that they are cell bodies of neurons. The surrounding nerve fibres are likely to be neuroglial cells, although the cytoplasm of these cells is not visible. The seemingly poor organisation of the tissues surrounding these neurons is often referred to as '''neuropil'''.
<br />
[[Image:WIKIVETspinalcord3.jpg|thumb|centre|350px|Spinal Cord 3 - © John Bredl]]
<br />
This image shows a further magnified view which displays the central canal and [[Ependymal Cells|ependymal cell]] layers. The surrounding tissue is similar to that of the grey matter neuropil seen in the previous image above. Within the central canal vessel some remnants of [[Cerebral Spinal Fluid - Anatomy & Physiology|CSF]] can be seen. Within the neuropil tissues, some cell bodies can be seen.

===Rabbit Spinal Cord===
<br />
[[File:Rabbitspinalcord40x.jpg|thumb|centre|350px|Rabbit Spinalcord at 40x Magnification]]
<br />
This image shows a moderately magnified image of the outer edge of the spinal cord. The bulk of the histological appearance is made up by white matter which is predominantly nerve fibres and myelin sheaths. This histological image clearly shows the different layering of protection around the outside of the spinal cord and how closely associated this protection is. The outer layer is the [[Meninges - Anatomy & Physiology#Dura_mater|dura mater]] and then continuing to move towards the spinal cord there is the [[Meninges - Anatomy & Physiology#Subdural_space|sub-dural space]] leading to the [[Meninges - Anatomy & Physiology#Arachnoid mater|arachnoid mater]]. Inside the arachnoid space is the [[Meninges - Anatomy & Physiology#Subarachnoid Space|sub-arachnoid space]] and then the [[Meninges - Anatomy & Physiology#Pia Mater|pia mater]] which is closely bound to the underlying neural tissues.

==Brain==
===Cerebrum section===
The [[Forebrain - Anatomy & Physiology|cerebrum]] contains the cell bodies of nerves both receiving and sending sensory information involved in controlling voluntary movement via motor activity and in the integration and coordination of other nerves. The cerebrum is also involved in memory functions.
<br />
<br />
In a full thickness histological image of the cerebrum it would be possible to distinguish numerous layers including the pia mater on the outer edge of the brain, the plexiform layer, pyramidal layer, granular layer and a polymorphic cell layer innermost, prior to the white matter towards the centre of the brain. The plexiform layer consists of mainly fibrous material which run in parallel to the surface of the brain. This layer contains relatively few cells, mainly neuroglial cells. The pyramidal cell layers mainly consist of small, medium and large pyramidal shaped cells which generally become larger as they become closer to the white matter of the cerebrum. Finally the pleomorphic layer contains cells of very diverse shapes, a majority of which have a spindle shape. These cells are often called fusiform cells.
[[Image:WIKIVETcerebrum.jpg|thumb|centre|350px|Cerebrum - © John Bredl]]
<br />
The histologic image above displays a very clear high magnification image of cell bodies with dendrites and axons extending from them. It should be noted that such a clear image of the nerve cells with their associated nerve fibres within the cerebrum is unusual and in most cases at a magnification of 350x a more detailed view of the types of cells found in the layers described above would be seen. A common stain for the cerebrum is Luxol blue which allows the visualisation of the plexiform cells, small to large pyramidal cells, granular cells and pleopmorphic cells. In most cases small capillaries are also usually visible, although none are present on the image above. Surrounding the neurons is the neuropil which is made up of densely packed aggregation of nerve fibres and neuroglial cells.

===Cerebellum section===
The [[Hindbrain - Anatomy & Physiology#Cerebellum|cerebellum]] lies behind the brain and below the level of the cerebrum. The cerebellum coordinates voluntary movements via controlling multiple muscle function as well as maintaining normal posture.
[[File:Cerebellum.jpg|thumb|centre|350px|Cerebellum]]
<br />
Although the above image is of a relatively poor quality, it is useful in displaying the general histologic appearance of the cerebellum. This cerebellum has been stained with haematoxylin and eosin (H&E) and shows the outermost '''molecular layer''' and the inner '''granular layer'''. The molecular layer stains more intensely with eosin whilst the granular layer stains more intensely with haematoxylin. Both of these layers make up the cortex of the cerebellum. Although not visible on this image, the granular layer contains a further, deeper area that stains less intensely with haematoxylin. This lighter central contains the white matter. In this image there is a moderate degree of detachment of the molecular layer from the granular layer which is due to the histology fixing process rather than the true physiological appearance.

On the outer edge of the molecular layer it is possible to visualise the pia mater fibrous covering. In the above image and as is common in cerebellar histology, the fixing process causes shrinkage of the pia mater resulting in an artefact appearance.
[[Image:WIKIVETcerebellum.jpg|thumb|centre|350px|Cerebellum - © John Bredl]]
<br />
This image shows a higher magnification of the junction between the molecular and granular layer. This junction contains a number of large cell bodies which are called '''Purkinje cells'''. Purkinje cells are characteristic of the histologic appearance of the cerebellum. Each cell has a number of dendrites that are within the molecular layer. The granular layer has a slightly darker mottled appearance which is made up of small neurons called '''Granule cells'''. These cells receive impulses from other parts of the CNS.

{{Template:Learning
|dragster = [[Types of Nervous Tissue Histology Resource (I)]]<br>[[Types of Nervous Tissue Histology Resource (II)]]
}}

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Alimentary System - Horse Anatomy

2022-10-27T19:42:02Z

Roytwv:

{{OpenPagesTop}}
==Introduction==
The horse is a monogastric hindgut fermenter. The horse evolved for grazing and it does so for up to 17 hours a day. A high proportion of the horse's dietary carbohydrate is in the form of '''starch'''. A mature horse eats 2-2.5% of it's body weight in dry matter every day, 1.5-1.75% of this should be fibre (hay/haylage). This is to prevent a rapid drop in pH in the large intestine and also to stimulate peristalsis in the gut and prevent build up of gas.

==Oral Cavity==
===[[Teeth - Anatomy & Physiology|Teeth]]===
[[Image:Horse teeth.jpg|thumb|right|200px|Tooth identifation in the horse - © Academy of Equine Dentistry-2008]]
[[Image:Horse Tooth.jpg|thumb|right|200px|Horse tooth - © Malcom Morley]]
'''Dental Formula'''
:The formula for '''deciduous''' teeth: 2 (I3/3 C0/0 P3/3)
:The formula for '''permanent''' teeth: 2 (I3/3 C1/1 P3-4/3 M3/3)

'''Canines'''
:The canines are '''rudimentary''' and are located in the '''diastema'''. The size of the [[Tooth - Anatomy & Physiology#Root|root]] is proportionally larger than the [[Tooth - Anatomy & Physiology#Crown|crown]].

'''Molars'''
:The molars have enlarged surfaces and higher [[Tooth - Anatomy & Physiology#Crown|crowns]]. They have delayed [[Tooth - Anatomy & Physiology#Root|root]] development and complicated folding of [[Tooth - Anatomy & Physiology#Enamel|enamel]].

'''Incisors'''
:Incisors have high [[Tooth - Anatomy & Physiology#Crown|crowns]] and folded [[Tooth - Anatomy & Physiology#Enamel|enamel]] surfaces. Their [[Tooth - Anatomy & Physiology#Root|roots]] converge.

'''Premolars'''
:A horse's '''Wolf tooth''' (PM1) is often lacking. Molars and Premolars form a continuous surface. The cheek teeth have a high rate of wear and continually erupt. The upper teeth are wider than the lower. There is no infundibulum in the lower teeth.

====Ageing====

Horses can be aged by their teeth. At two and a half years of age the first permanent incisor will erupt; at three and a half the second permanent incisor will erupt and at four and a half the third permanent incisor will erupt. Over five years of age the folding of the enamel ring ('''infundibulum''') can indicate age. There is a seven year hook and over 13 years of age a '''dental star''' will be present.

The '''Galvayne's Groove''' is a brown groove on the upper corner incisor teeth and indicates that the horse is over 10 years old. At 15 the groove will be approximately half way down the tooth; At 20 the groove will run down the whole tooth; Over 20 the groove begins to disappear; At 25 the groove will only be visible on the bottom half of the tooth. At 30 the groove will usually be gone.

===Palate===
Horses have a tight laryngeal cuff around the laryngeal entrance, therefore the [[Soft Palate|soft palate]] cannot be raised for long periods of time. This causes them to be obligate nasal breathers. Laryngeal cuffing also prevents [[Vomiting|vomiting]]. There are no specific species diferences in the [[Hard Palate|hard palate]].

==[[Oesophagus - Anatomy & Physiology|Oesophagus]]==
In the horse, the oesophageal lumen narrows at the thoracic inlet and oesophageal hiatus of the diaphragm; this predisposes them to impaction (choke). Another factor specific to horses is that striated muscle exists only in the rostral 65% of the oesophagus.

==Stomach==
[[Image:Margo Plicatus.jpg|thumb|right|250px|Equine Stomach with Margo Plicatus - © RVC 2008]]
The horse has a [[Monogastric Stomach - Anatomy & Physiology|monogastric stomach]] located on the left side of the abdomen. A region called the '''margo plicatus''' is present which separates the glandular and non-glandular parts of the equine stomach. The non-glandular area is lined with squamous epithelium (not columnar).

The stomach is relatively small (10% GIT) and its capacity is 8-16 litres. The equine stomach is rarely empty, retention time is short and expulsion into the [[Duodenum - Anatomy & Physiology|duodenum]] stops when feeding stops. Although fluid exits quickly, feed particles can be retained for more than 48 hours as digestion is initiated in the stomach. A 500kg horse can produce 30 litres of gastric juice in 24 hours. The strong '''cardiac sphincter''' allows movement of gas and fluid into the stomach, but not out of it. This prevents the animal from [[Vomiting|vomiting]]. Therefore, any disorder that results in aboral fluid movement from the small intestine results in fluid accumulation in the stomach (gastric reflux), [[Gastric Dilation and Rupture - Horse|dilation and eventually gastric rupture]] if left untreated.

==[[Small Intestine Overview - Anatomy & Physiology|Small Intestine]]==
===Duodenum===
[[Image:Section of duodenum from horse.JPG|thumb|right|250px|Section of equine duodenum- © RVC 2008]]
The descending duodenum is dorsal on the right side of the abdomen, suspended from the dorsal body wall by the mesoduodenum. The mesoduodenum is relatively short, so the duodenum is closely tethered in a constant position. In the right paralumbar fossa region, the descending duodenum turns towards the midline and is attached to the base of the [[Caecum - Anatomy & Physiology|caecum]]. The descending duodenum then runs caudally beneath the [[Liver - Anatomy & Physiology|liver]] to the caudal pole of the right kidney where it has its caudal flexure to become the ascending duodenum.

===Jejunum===
The jejunum is confined to the left dorsal part of the abdomen associated with a long mesentery. It is restricted to this position by the large [[Caecum - Anatomy & Physiology|caecum]] on the right, and ascending [[Colon - Anatomy & Physiology|colon]] ventrally on both sides.

===Ileum===
The terminal portion of the small intestine is the ileum, which joins the caecum at its dorso-medial aspect. The ileal mesentery attaches to the [[Caecum - Anatomy & Physiology|caecum]] at the dorsal caecal band.

==[[Large Intestine Overview - Anatomy & Physiology|Large Intestine]]==

Undigested material spends a long time in the [[Caecum - Anatomy & Physiology|caecum]] and [[Large Intestine - Anatomy & Physiology|large intestine]] undergoing microbial fermentation, mainly of cellulose (95% after 65 hours).

In the hindgut of the horse; 75-85% of insoluble carbohydrates is digested, 15-30% of soluble carbohydrates and 30% of protein is digested. A lot of absorption of [[Volatile Fatty Acids|volatile fatty acids (VFAs)]] and water occurs in the large intestine which pass readily into the blood. Electrolytes are also absorbed in the large intestine; 95% of sodium and chloride and 75% of potassium and phosphate.
To mix the contents of the large intestines, the taenia and circular muscle of the tunica muscularis contract. This also transports the ingesta through the large intestine and brings the products of fermentation in contact with the epithelium.

===[[Caecum - Anatomy & Physiology|Caecum]]===

The caecum is the main site of microbial fermentation, followed by the ascending then descending [[Colon - Anatomy & Physiology|colons]]. It is located on the right side of the abdomen. It is very large, roughly 1m in length with a 30L capacity. It consists of a base, body and apex (blind ending). The base lies in the right dorsal part of the abdomen, in contact with the abdominal roof. The apex lies on the ventral abdominal wall, and terminates at the level of the '''xiphoid cartilage'''. It exists at the junction with the [[Ileum - Anatomy & Physiology|ileum]] and [[Colon - Anatomy & Physiology|colon]].

The '''caecocolic orifice''' is where the caecum opens into the ascending colon. This exists as a transverse slit formed by a constriction of the ascending colon. There is a sphincter at this point which prevents backward flow of ingesta when the colon contracts.

The ileum opens into the caecum at the '''ileal papilla'''. This is a small projection into the caecum housing the ileal sphincter and venous plexus that, together, control the ileal orifice.

'''Taeniae''' are present. Taeniae are formed by concentration of the ''longitudinal'' muscle layer. Between the taeniae are sacculations, or '''haustra'''. Haustra appear as folds on the interior surface. There are '''four''' taeniae over the [[Caecum - Anatomy & Physiology|caecum]]; dorsal, ventral, lateral and medial. The '''dorsal''' taenia provides the attachment site for the ileocaecal fold, which joins the caecum to the [[Ileum - Anatomy & Physiology|ileum]].

The '''lateral''' taenia provides the attachment site for the caecocolic fold, which joins the caecum to the ascending [[Colon - Anatomy & Physiology|colon]]. The '''ventral''' taenia is free.

The '''medial''' and '''lateral''' taeniae are where the caecal vessels and [[Lymph Nodes - Anatomy & Physiology|lymph nodes]] are located. Ingesta is regularly transported from the [[Ileum - Anatomy & Physiology|ileum]] to the [[Caecum - Anatomy & Physiology|caecum]], this movement can be heard upon auscultation of the right dorsal quadrant of the caudal abdomen.
[[Colic Diagnosis - Abdominal Auscultation|Ausculatation of this area]] is carried out in the assessment of [[:Category:Colic in Horses|colic]]. In the horse, the [[Caecum - Anatomy & Physiology|caecum]] is responsible for the digestion of complex carbohydrates such as cellulose.

===[[Colon - Anatomy & Physiology|Colon]]===

====Ascending Colon====
The ascending colon is very large and takes up most of the ventral abdomen. It is the shape of a double "U", where one "U" is on top of the other. There are four limbs that lie parallel to each other, and three flexures that change these direction of the limbs.

The sequence of the limbs and flexures of the ascending colon is as follows; '''Right Ventral Colon''' ''(for those with an RVC bias remember, "the RVC comes first!")'', passes out of the caecocolic orifice on the right side of the abdomen and continues cranially to the xiphoid region; '''Sternal Flexure''', passes across the midline from right to left, '''Left Ventral Colon''', runs caudally on the left ventral abdominal floor; '''Pelvic Flexure''', turns dorsally just cranial to the pelvic inlet and then runs cranially to the diaphragm, '''Left Dorsal Colon''', runs cranially, parallel and dorsal to the left ventral colon; '''Diaphragmatic Flexure''', turns caudally at the diaphragm; '''Right Dorsal Colon''', continues caudally on the right. It is the shortest limb of the ascending colon.

The '''transverse colon''' continues on from the right dorsal colon as the right dorsal colon turns medially. The right dorsal colon is attached by a mesentery to the dorsal abdominal wall, the base of the [[Caecum - Anatomy & Physiology|caecum]], the root of the mesentery and the [[Pancreas - Anatomy & Physiology|pancreas]]. This anatomical arrangement of mesentery allows the left ascending colon to twist and is a common cause of [[:Category:Colic in Horses|colic]] ([[Large Colon Torsion - Horse|colonic torsion]]).

The ventral parts of the ascending colon are attached to the dorsal parts by a short '''mesocolon'''. The mesocolon houses the blood vessels, nerves and lymphatics. In the ventral colon many important digestive and absorptive functions take place, whilst the dorsal colon is mainly responsible for transportation of ingesta. '''Taeniae''' are present. Different parts of the colon can be distinguished by the number of taeniae present:

The right and left ventral colon and the sternal flexure have '''four''' taeniae. The left dorsal colon and pelvic flexure have '''one''' taenia and the right dorsal colon and diaphragmatic flexure have '''three''' taeniae.

====Transverse Colon====

The transverse colon is short. It passes from across the midline from right to left. It passes cranial to the root of the mesentery. It has '''two''' taeniae. It turns caudally to become the descending colon at the level of the [[Urinary System Overview - Anatomy & Physiology|left kidney]].

====Descending Colon====

The descending colon is between 2-4 meters long. It is suspended by a long mesentery; ''mesocolon descendens''. The descending colon has '''two''' taeniae. Between the two taeniae are distinct sacculations that house the faecal balls.

===[[Rectal Examination of the Horse|Rectal Palpation]]===

[[Rectal Examination of the Horse|Rectal palpation]] is a useful technique and is often used to assess [[:Category:Colic in Horses|colic]]. Structures that can be palpated ''per rectum'' include; faecal balls in the descending colon, the [[Urinary Bladder - Anatomy & Physiology|bladder]], the [[Reproductive System Overview - Anatomy & Physiology|reproductive organs]] in the mare, the base of the [[Caecum - Anatomy & Physiology|caecum]], the root of the mesentery, the [[Urinary System Overview - Anatomy & Physiology|left kidney]], +/- the nephrosplenic ligament, the left dorsal colon and the pelvic flexure of the ascending colon. ''NB: This is a common site of impaction.''

===Microbial Environment===

Microbes convert carbohydrates to [[Volatile Fatty Acids|volatile fatty acids]] (VFAs). The horse receives 75% of its energy requirements from VFAs. The large intestine is buffered by the secretion of large amounts of bicarbonate from the [[Pancreas - Anatomy & Physiology|pancreas]] and the [[Ileum - Anatomy & Physiology|ileum]]. Glands in the wall of the [[Large Intestine - Anatomy & Physiology|large intestine]] may also produce bicarbonate. The microbial population exists in the [[Caecum - Anatomy & Physiology|caecum]] and ventral colon.

The environment is mixed; there are both bacteria and protozoa. Microbes are anaerobic. The microbial population is dependent on diet and frequency of feeding, as different microbes are suited to digesting different particles. The number of microbes can change 100 fold in a 24 hour period. [[Volatile Fatty Acids|VFAs]] produced are absorbed across the intestinal wall. Urea from the blood is transported to the intestinal lumen to be used by microbes, which also use nitrogen from the diet. Environmental factors of the [[Caecum - Anatomy & Physiology|caecum]] and ventral colon can influence fermentation of microbial population.

Environmental factors include: frequent intake of food, constant temperature, constant mixing, removal of the products of fermentation by absorption and peristalsis and the stable osmotic environment i.e. normal intake of water.

[[Volatile Fatty Acids|VFA's]] produced include Acetate, Propionate and Butyrate. Factors that promote VFA production include an optimum pH of 6.5, an anaerobic environment and gut motility.

==[[Liver - Anatomy & Physiology|Liver]]==
The liver is contained entirely within the rib cage, to the right of the midline. It is less lobated than in other species. The larger right lobe is undivided, and the left lobe subdivided. The caudate lobe is notched at the ventral free border. There is no papillary process. Horses have no [[Gall Bladder - Anatomy & Physiology|gall bladder]], and the hepatic ducts are relatively wide as a result. In the foal, the liver is larger and more symmetrical. The bile duct opens into the [[Duodenum - Anatomy & Physiology|duodenum]] at the same papillae as the major pancreatic duct. Bile is constantly secreted.

==[[Pancreas - Anatomy & Physiology|Pancreas]]==
The pancreas lies mainly on the right, in the very dorsal part of the abdomen. It is triangular in shape and lies within the sigmoid flexure of the [[Duodenum - Anatomy & Physiology|duodenum]]. The lobes are less distinguishable compared to the dog. The ventral surface is directly attached to the right dorsal [[Colon - Anatomy & Physiology|colon]] and base of the [[Caecum - Anatomy & Physiology|caecum]]. The dorsal surface is directly attached to the right kidney and [[Liver - Anatomy & Physiology|liver]]. The portal vein perforates the pancreas at the '''pancreatic ring'''. Both the pancreatic and accessory ducts persist throughout development. There is a constant secretion of pancreatic juice, which increases after feeding. This provides the caecum and colon with a constant supply of buffered solution, which maintains a stable environment important for microbe survival.

{{Template:Learning
|flashcards = [[Hindgut Fermenters - Horse - Anatomy & Physiology - Flashcards|Horse digestive system]]
|videos = [[Video: Foal gastrointestinal tract potcast|Foal gastrointestinal tract potcast]]<br>[[Video: Abdominal viscera of the horse dissection|Abdominal viscera of the horse dissection]]<br>[[Video: Equine left-sided abdominal and thoracic topography dissection|Equine left-sided abdominal and thoracic topography dissection]]<br>[[Video: Equine left-sided abdominal and thoracic topography dissection 2|Equine left-sided abdominal and thoracic topography dissection 2]]<br>[[Video: Equine stomach potcast|Equine stomach potcast]]<br><br>
|OVAM = [http://www.onlineveterinaryanatomy.net/content/equine-head-and-dentition-powerpoint PowerPoint covering the anatomy and physiology of the equine head and dentition, including the skeletal aspects, the physiology of mastication and it’s associated anatomy as well as common dental abnormalities.]<br>[http://www.onlineveterinaryanatomy.net/content/horse-caecum-and-colon-left-view Equine Caecum and Colon - Left View]<br>[http://www.onlineveterinaryanatomy.net/content/horse-caecum-and-colon-right-view Equine Caecum and Colon - Right View]<br>[http://www.onlineveterinaryanatomy.net/content/equine-oesophagus-histology Equine Oesophagus Histology]<br>[http://www.onlineveterinaryanatomy.net/content/equine-duodenum-histology Equine Duodenum Histology 1]<br>[http://www.onlineveterinaryanatomy.net/content/equine-duodenum-histology-0 Equine Duodenum Histology 2]<br>[http://www.onlineveterinaryanatomy.net/content/smooth-muscle-histology-equine-duodenum-0 Smooth Muscle Histology of Equine Duodenum]
}}

==Webinars==
<rss max="10" highlight="none">https://www.thewebinarvet.com/gastroenterology-and-nutrition/webinars/feed</rss>
[[Category:Horse Anatomy]]

Pancreas - Anatomy & Physiology

2022-10-27T19:41:06Z

Roytwv:

{{OpenPagesTop}}
==Introduction==

The pancreas is a tubuloalveolar gland and has '''exocrine''' and '''[[Endocrine System Overview - Anatomy & Physiology|endocrine]]''' tissues. The '''exocrine''' is the larger of the two parts and secretes pancreatic juice; a solution containing enzymes for carbohydrate, protein and triacylglycerol digestion. Pancreatic juice drains into the [[Small Intestine Overview - Anatomy & Physiology|small intestine]] where it is functional. The '''endocrine''' part secretes hormones for the regulation of blood glucose concentration, including insulin, glucagon and somatostatin. The functional units of the endocrine part are the ''islets of Langerhans''.

===Development===

The pancreas develops from endoderm, except for the connective tissue which develops from splanchnic mesoderm. Development begins with evaginations of the digestive tube caudal to the [[Monogastric Stomach - Anatomy & Physiology|stomach]]. Two pancreatic buds form, one in the dorsal mesogastrium and one in the ventral mesogastrium. Some epithelial cells lose their connections to the developing duct system of the exocrine pancreas and develop into the islets of Langerhans of the endocrine pancreas. As the stomach rotates, the ventral bud moves to become more dorsal. The two buds then fuse; the left lobe is derived from the dorsal bud and the right lobe from the ventral bud. The duct of the ventral lobe ('''pancreatic duct''') joins with the bile duct to form the '''common bile duct''' which opens into the duodenum at the '''major duodenal papilla'''. The duct of the dorsal lobe ('''accessory duct''') enters the [[Duodenum - Anatomy & Physiology|duodenum]] at the '''minor duodenal papilla'''. There is [[#Species Differences|species variation]] in the persistence of each duct.

==Structure==
[[Image:Sheep Pancreas.jpg|thumb|right|250px|Pancreas (Sheep) - © RVC 2008]]
The pancreas is located in the craniodorsal part of the abdomen in close association with the [[Duodenum - Anatomy & Physiology|duodenum]]. It can be divided into three parts; a body and left and right lobes. The lobes are loosely united by interlobular connective tissue. Connective tissue contains blood vessels, nerves and lymphatics. Generally, the portal vein runs between the left and right lobes (see [[#Species Differences|species differences]]). The pancreas is roughly "V" shaped in all species. As mentioned in the [[#Development|development]] section, there are two ducts present in the pancreas. Their presence reflects the convergent development pattern of the pancreas, however in some species one or other of the ducts may atrophy. The '''pancreatic duct''' is the biggest of the two and opens into the duodenum with the bile duct at the major duodenal papilla. The '''accessory duct''' opens on the opposite aspect of the duodenum at the minor duodenal papilla.

==Exocrine Function==

'''Alkaline Secretion'''

Pancreatic juice discharges into the duodenum through ducts. It is alkaline as it contains '''bicarbonate''' and '''chloride ions'''. Bicarbonate ions are actively transported into the duct lumen. Water follows passively by osmosis. The osmolarity of the pancreatic juice is equivalent to the osmolarity of the blood. Pancreatic juice is alkaline to neutralise the acidic gastric juice. This is advantageous because: It provides an optimal pH for the pancreatic enzymes and it prevents damage to the thin, absorptive mucosa of the duodenum. Its alkalinity also helps to buffer the [[Large Intestine - Anatomy & Physiology|large intestine]] which is important in [[Hindgut Fermenters - Anatomy & Physiology|hindgut fermenters]].

'''Enzymatic Digestion'''

The alkaline secretion contains digestive enzymes that can digest protein, carbohydrates and lipids. Digestion is discussed in the [[Small Intestine Overview - Anatomy & Physiology|small intestine overview]].

The following table lists the enzymes secreted by the pancreas and their effects:

{| style="width:75%; height:200px" border="1"

!'''Enzyme'''
!'''Substrate'''
!'''Action'''

|-
| '''Trypsin, Chymotrypsin, Elastase'''
| Peptides
| Endopeptidases; cleave bonds between amino acids
|-
| '''Carboxypeptidase and Aminopeptidase'''
| Peptides
| Exopeptidases; cleave bonds at the terminus of a peptide
|-
| '''α - amylase'''
|Polysaccharides: starch and glycogen
|Endoglycosidase; cleaves bonds between carbohydrate monomers to produce maltose and short carbohydrate chains.
|-
| '''Pancreatic lipase'''
|Triacylglycerols and 1,2 - diacylglycerols
|Fatty acids, glycerol and 2 - monoacylglycerol
|}

==Endocrine Function==

Functional units are the '''islets of Langerhans''', which are embedded throughout the exocrine tissue. Cells of the islets produce hormones that maintain normoglycaemia. Glucagon raises the blood glucose level and insulin decreses the blood glucose level. Somatostatin acts in a paracrine fashion to inhibit both glucagon and insulin secretion. Pancreatic polypeptide is thought to be a cholecystokinin antagonist, and thus inhibits secretion of pancreatic juice.

See here for more information on [[Glucagon]] and [[Insulin]].

===[[DM|Diabetes Mellitus]]===
[[Image:NIDDM cat.jpg|thumb|right|250px|An obese cat with NIDDM - © RVC 2008]]

A condition characterised by an inability to maintain normoglycaemia, with persistent hyperglycaemia observed.
Clinical signs include: glucosuria, polyuria and polydipsia - blood glucose concentration exceeds the renal threshold (~10mmol/l) and is excreted into the urine. The increased osmotic potential of the filtrate draws water into the filtrate which is lost in the urine. The animal drinks more to compensate for water loss. Polyphagia and weight loss are also seen where the animal compensates for persistent loss of glucose. Ketosis and ketonuria are also seen, where ketones are released for energy.

===Types of diabetes in dogs===

'''β cell deficiency''' - The majority of cases of [[DM|diabetes mellitus]] seen in dogs are of this kind. It causes an inability to produce insulin. It can be caused by congenital defects, pancreatitis and autoimmunity.

'''Insulin antagonism''' - Seen in females in dioestrus, or in animals with [[Neoplasia - Pathology|Cushing's]] (hyperadrenocorticism). [[Ovaries Endocrine Function - Anatomy & Physiology|Progesterone]], [[Pituitary Growth Hormone - Anatomy & Physiology|growth hormone]] and cortisol are insulin antagonists.

===Types of diabetes in cats===

'''Insulin Dependant Diabetes Mellitus (IDDM)'''; insulin deficiency - similar to human diabetes type 1. There is a failure to produce insulin. This can be caused by islet-specific amyloidosis or chronic pancreatitis leading to β cell destruction.

'''Non Insulin Dependant Diabetes Mellitus (NIDDM)'''; insulin antagonism - similar to human diabetes type 2. Caused by obesity which leads to carbohydrate intolerance.

==Vasculature==

The pancreas receives its blood supply from the '''coeliac''' and '''cranial mesenteric''' as branches from the splenic, hepatic and superior mesenteric arteries. The right lobe receives blood from the '''cranial pancreatoduodenal artery'''; a branch of the hepatic artery. The left lobe receives blood from the splenic artery and '''caudal pancreatoduodenal artery'''; a branch of the cranial mesenteric artery. Vessels aborize within the connective tissue septa and give off rich capillary networks that surround each acinus and invade each islet. The endothelium in the exocrine pancreas is continuous, whereas the endothelium of capillaries surrounding the islets in the endocrine pancreas are fenestrated. The pancreas is drained by veins that open into the portal vein. The islets receive ample blood supply to enable an appropriate response to blood glucose level.

==Innervation==

The pancreas receives sympathetic and parasympathetic supply. The parasympathetic is supplied by the dorsal vagal trunk and the sympathetic is supplied by the solar plexus (splanchnic nerves). Parasympathetic and sympathetic stimulation results in exocytosis and accumulation of secretory vesicles in the lumen and ducts of the acini. Nervous regulation is thought to be of lesser importance than hormonal control. Hormones that increase pancreatic secretion include: cholecystokinin (CCK), secretin and gastrin. There is some negative feedback from somatostatin and enkephalins.

==Lymphatics==

Blind ending lymphatic vessels drain into larger lymphatic vessels that follow the course of the blood vessels in the connective tissue. Lymph drains into the '''pancreaticoduodenal''' lymph nodes. It then drains into the coeliac centre, which surrounds the coeliac artery.

==Histology==
===Exocrine===
[[Image:Islet and acini.jpg|thumb|right|250px|Acini and islet of Langerhans - © RVC 2008]]
The exocrine pancreas consists of '''acini''', which resemble bunches of grapes. Each acinus consists of a single layer of 40 - 50 pyramidal epithelial cells surrounding a lumen. The epithelial cells produce the secretion (pancreatic juice) containing enzymes, ions and water. The cells become wider during active secretion. The base of the acinar cells are strongly basophilic owing to the presence of endoplasmic reticulum, where there is a high concentration of RNA. This part of the cell therefore stains darker with haematoxylin and eosin. The apex of the cells is abundant with secretory granules containing the zymogen precursors of the pancreatic enzymes. The number of secretory granules increases after fasting, and decreases after a meal.

The lumen of the acini drain into the '''intercalated duct'''. Intercalated ducts converge to make larger interlobular ducts, which in turn converge to make interlobar ducts. '''Interlobar ducts''' are found in the connective tissue septa between lobules. Interlobar ducts join to form either the '''pancreatic''' or the '''accessory duct''', these ducts drain into the duodenum. In some cases, the pancreatic duct unites with the bile duct, and bile and pancreatic juice enter the duodenum together.

===Endocrine===

[[Image:Islet cell types.jpg|thumb|right|250px|Islet of Langerhans - © RVC 2008]]
In the endocrine pancreas, the '''islets of Langerhans''' are embedded in the exocrine tissue. Each islet is composed of 2 - 3 thousand epithelial cells. The epithelial cells are arranged in a compact structure that is pervaded by a capillary network. A thin layer of reticular fibres separates the islets from the surrounding exocrine tissue. There are ''four'' different cell types within the islets of Langerhans that each produce different hormones, they include:

'''α cells'''- Produce glucagon, typically located at the periphery of the islet. They are not present in all islets.

'''β cells'''- Produce insulin. The predominant cell type, located in the centre of the islet and contributing to 70% of all cells.

'''δ cells'''- Produce somatostatin. There are low numbers in all islets.

'''F cells'''- Produce pancreatic polypeptide and are few in number, they may be present in the exocrine tissue also.

==Species Differences==

===Carnivore===

Carnivores have a pancreas that is clearly distinguishable as a body and left and right lobes. The portal vein runs dorsally between the left and right lobes. The '''left lobe''' is smaller than the right. The tip of the left lobe contacts the left kidney and lies in the greater omentum. The '''right lobe''' follows the descending duodenum and lies in the mesoduodenum. Dorsally, it is related to the visceral surface of the [[Liver - Anatomy & Physiology|liver]] and the ventral surface of the right kidney. Ventrally, it is related to the descending [[Duodenum - Anatomy & Physiology|duodenum]]. Laterally it is related to the ascending [[Colon - Anatomy & Physiology|colon]]. In dogs, both pancreatic and accessory ducts persist throughout development. However, the pancreatic duct is smaller. It joins the bile duct just before opening into the major duodenal papilla which lies 3-6cm distal to the pylorus of the [[Monogastric Stomach - Anatomy & Physiology|stomach]]. The accessory duct is the bigger duct and opens 3-5cm further distally to the pancreatic duct. The two ducts communicate inside the pancreas.

In cats, the distal part of the accessory duct atrophies during development, so only the pancreatic duct persists. Cats normally have pacinian corpuscles in the interlobular tissue that are visible grossly being 1-3cm in diameter. Dogs and cats produce little pancreatic juice between meals, but lots during a meal.

===Ruminant===

The pancreas of a ruminant consists of a distinguishable short body and left and right lobes. The '''left lobe''' lies in the retroperitoneal space and is in contact with the liver, diaphragm and major vessels dorsally. Ventrally, it is in contact with intestines and dorsal sac of the [[Rumen - Anatomy & Physiology|rumen]]. The '''right lobe''' is larger and lies in the mesoduodenum against the flank of the animal and runs part of the length of the descending duodenum. The portal vein passes dorsally at the pancreatic notch between the left and right lobes. In the ox, the distal part of the pancreatic duct atrophies during development, so only the accessory duct persists. The accessory duct enters the duodenum 20 to 25cm distal to the entry of the bile duct. In sheep and goats the distal part of the accessory duct atrophies during development, so only the pancreatic duct persists. It unifies with the bile duct so that both enter via a common duct. There is a constant secretion of pancreatic juice.

===Equine===

The pancreas lies mainly on the right, in the very dorsal part of the abdomen. It is triangular in shape and lies within the sigmoid flexure of the [[Duodenum - Anatomy & Physiology|duodenum]]. The lobes are less distinguishable compared to the dog. The ventral surface is directly attached to the right dorsal [[Colon - Anatomy & Physiology|colon]] and base of the [[Caecum - Anatomy & Physiology|caecum]]. The dorsal surface is directly attached to the right kidney and [[Liver - Anatomy & Physiology|liver]]. The portal vein perforates the pancreas at the '''pancreatic ring'''. Both the pancreatic and accessory ducts persist throughout development. There is a constant secretion of pancreatic juice, which increases after feeding. This provides the caecum and colon with a constant supply of buffered solution, which maintains a stable environment important for microbe survival.

===Porcine===

The pancreas consists of a large body and left lobe, with a much smaller right lobe. The portal vein perforates the pancreas. The distal part of the pancreatic duct atrophies during development, so only the accessory duct persists. Two thirds lie to the left of the midline. The right portion lies adjacent to the descending duodenum and its cranial border contacts the liver. The left portion is related to the [[Spleen - Anatomy & Physiology|spleen]], cranial pole of the [[Urinary System Overview - Anatomy & Physiology|left kidney]] and the fundus of the [[Monogastric Stomach - Anatomy & Physiology|stomach]].

==Links==

'''Click here for information on [[:Category:Pancreas - Pathology|pathology of the pancreas]]'''

{{Template:Learning
|flashcards = [[Pancreas - Anatomy & Physiology - Flashcards|Pancreas flashcards]]
|videos = [[Video: Feline Abdomen|Feline Abdomen potcast]]<br>[[Video: Bovine liver potcast 2|Bovine liver potcast 2]]<br>[[Video: Foal gastrointestinal tract potcast|Foal gastrointestinal tract potcast]]<br>[[Video: Ventral view of the pancreas and small intestine potcast|Ventral view of the pancreas and small intestine potcast]]<br>[[Video: Bovine pregnant uterus potcast 2|Bovine pregnant uterus potcast 2]]
|powerpoints = [[Gastrointestinal Tract Histology resource|Histology of the pancreas - see part 2]]
|Vetstream = [https://www.vetstream.com/canis/search?s=pancreas Pancreatic diseases]
}}

==Webinars==
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[[Category:Alimentary System - Anatomy & Physiology]]
[[Category:Pancreas]]
[[Category:A&P Done]]
[[Category:Endocrine System - Anatomy & Physiology]]

Bovine Hindlimb - Anatomy & Physiology

2022-10-27T19:39:44Z

Roytwv:

{{OpenPagesTop}}
==Pelvic Girdle and Hip==
===Bones===
The pelvic girdle is formed by two hip bones which are joined ventrally at the cartilagenous '''pelvic symphysis''' and articulate dorsally with the sacrum. The three components of each hip bone are the [[Hindlimb - Anatomy & Physiology#Ilium |Ilium]], [[Hindlimb - Anatomy & Physiology#Pubis|pubis]] and [[Hindlimb - Anatomy & Physiology#Ischium|ischium]].

The bone that articulates with the hip bones to form the hip joint is the [[Hindlimb - Anatomy & Physiology#Femur|Femur]].

====Bovine Bone Specifics====

*'''[[Hindlimb - Anatomy & Physiology#Ilium|Ilium]]'''
**In the cow the '''tuber coxae''' is visible and is readily palpable.
**The '''sacral tuber''' has two prominences; the cranial and caudal dorsal iliac spines.
**The '''iliac crest''' is thin and concave.
**The '''ileal wing''' is orientated in a vertical manner.

*'''[[Hindlimb - Anatomy & Physiology#Ischium|Ischium]]'''
** The '''ischial tuberosity''' is triangular in shape.

*'''[[Hindlimb - Anatomy & Physiology#Femur|Femur]]'''
** The '''greater trochanter''' extends further dorsally compared to the femoral head.
** The medial and lateral condylar ridges are very assymetrical with the medial ridge being larger.

==Joints and Synovial Structures==

====[[Hindlimb - Anatomy & Physiology#Sacroiliac Joint|Sacroiliac Joint]]====

* In cattle the short branch of the '''dorsal sacroiliac ligaments''' connects the sacral tuberosity to the spinous processes of the sacrum.
* The '''sacrotuberous ligament''' is a broad sheet-like ligament, which extends between the lateral aspect of the sacrum and the dorsal border of ischium and ilium. In this ligament are the '''lesser and greater ischiatic foramen''', these are present to allow for blood vessels, nerves and tendons. The caudal border of this ligament is visible subcutaneously.

====[[Hindlimb - Anatomy & Physiology#Coxafemoral/Hip Joint|Coxafemoral/Hip Joint]]====
* The cow has the most limited range of movement compared other domestic species in its hip. This is mainly restricted to flexion and extension and is a result of the conformation of its femoral head, intraarticular ligaments and a large muscle mass around the joint.
* Cattle also have an extra acetabular notch on it's cranioventral aspect.

==Musculature==

The muscles affecting the pelvic girdle and hip can be divided into two distinct groups:

* '''[[Hindlimb - Anatomy & Physiology#Girdle Musculature|Girdle Musculature]]'''
** '''Psoas minor''' - the muscle is marked by many tendinous intersections
** '''Iliac muscle''' - a fleshy muscle that is cross-sectionally flat cranially and round caudally. It originates from two heads; a strong lateral head from the wing of the ilium and a small medial one from the ileal shaft. They enclose the '''greater psoas''' and will unite to form a common tendon for insertion.
** '''Quadrate Lumbar''' - a thin tendinous muscle whose origin is at the proximal end of the last rib and the transverse process of the cranial lumbar vertebrae. Its insertion is the transverse processes of the caudal lumbar vertebrae and the sacral wing.

* '''[[Hindlimb - Anatomy & Physiology#Rump Muscles|Rump Muscles]]'''
** '''Superficial gluteal'''
*** It is totally fused with the biceps muscle of the thigh forming the '''gluteobiceps'''.
** '''Middle Gluteal'''
*** Origin - the gluteal surface of the ilium. The muscle is flat at its origin and so the iliac crest is very palpable.
*** Insertion - The short portion inserts on the greater trochanter, the deep portion inserts on both the greater trochanter and distal and medial to it.
**'''Deep Gluteal'''
*** Insertion - distal to the greater trochanter on the craniolateral aspect of the femur.
**'''Tensor Muscle of the Fascia Lata'''
*** Origin - coxal tuberosity
*** Insertion - it joins the fascia lata and so indirectly attaches to the patella, lateral pattelar ligament and cranial border of the tibia. A caudodorsal detachment joins the superficial gluteal and so attaches to the greater trochanter.
** '''Gluteobiceps'''
*** Origin - Vertebral head - caudal sacral vertebrae, sacrotuberous ligament and ischial tuberosity. Pelvic head - venterolateral aspect of the ischium from the ischiatic tuberosity to the obturator foramen.
*** Insertion - the two bellies unite and the redivide at mid-tibia level. The cranial belly attaches to the fascia lata and crural fascia and so inserts on the patella, the lateral patellar ligament and the tibial tuberosity. The cranial part forms the tarsal tendon and so inserts on the calcaneal tuberosity.
*** A synovial bursa exists between the tarsal tendon and lateral femoral condyle.
** '''Semitendinous'''
*** Origin - caudoventral aspect of the ischial tuberosity.
*** Insertion - via a flat aponeurotic tendon to the cranial border of the proximal tibia, the crural fascia and the tendinous insertion of the gracilis muscle. An accessory tendon also inserts on the calcaneal tendon.
** '''Semimembranous'''
*** Origin - it just has one from the pelvic head.
** '''Sartorius'''
*** Origin - It is divided briefly into two heads because of the passage of femoral vessels.
** '''External Obturator'''
*** Cattle have an extra intrapelvic part that originates from the ilial body, the pubis and ischium. This then inserts with the rest of the muscle on the trochantic fossa.

==Proximal Hindlimb including Stifle and Tarsus==
===Bones===

The bones immediately distal to the [[Hindlimb - Anatomy & Physiology#Femur|femur]] are the [[Hindlimb - Anatomy & Physiology#Tibia|tibia]], [[Hindlimb - Anatomy & Physiology#Fibula|fibula]], [[Hindlimb - Anatomy & Physiology#Patella|patella]] and some minor sesamoid bones. Some of these are involved in the stifle joint, weight-bearing and providing attachment for muscles.

Distal to these bones are the complex series of bones that make up the tarsus, these are the [[Hindlimb - Anatomy & Physiology#Tarsal bones|tarsal bones]] and [[Hindlimb - Anatomy & Physiology#Metatarsals|metatarsals]].

====Bovine Bone Specifics====

*'''[[Hindlimb - Anatomy & Physiology#Patella|Patella]]'''
** The patella is extended medially by fibrocartilage.

*'''[[Hindlimb - Anatomy & Physiology#Tibia|Tibia]]'''
** The lateral aspect of the condyle has no articular facet as the [[Hindlimb - Anatomy & Physiology#Fibula|fibula]] is directly fused to the [[Hindlimb - Anatomy & Physiology#Tibia|tibia]] at this point.
** The lateral aspect of the cochlea has an articular facet as the '''malleolar bone''', the remnant of the distal fibula, articulates here.

*'''[[Hindlimb - Anatomy & Physiology#Fibula|Fibula]]'''
** The shaft of the fibula is totally absent.
** The proximal head is fused to the tibia.
** The distal part remains as the '''malleolar bone''', which articulates with the [[Hindlimb - Anatomy & Physiology#Tibia|tibia]].

*'''[[Hindlimb - Anatomy & Physiology#Tarsal bones#Talus|Talus]]'''
** The trochlear ridges lie in a sagittal direction and articulates with the medial malleolus medially and the mlleolar bone laterally.
** The distal trochlear is well defined, articulating with the combined 4th and central tarsal bones.

*'''[[Hindlimb - Anatomy & Physiology#Tarsal bones|Calcaneus]]'''
** The calcaneal tuberosity's proximal aspect is roughened and hollowed out.

*'''[[Hindlimb - Anatomy & Physiology#Tarsal bones#Distal Row of Tarsal Bones| Distal Row of Tarsal Bones]]'''
** The cow only has three bones in the distal row, with the 1st tarsal bone being the only one left unfused. The 2nd and 3rd tarsal bones are fused together. The central and 4th tarsal bones are also fused.

===Joints and Synovial Structures===

'''[[Hindlimb - Anatomy & Physiology#Stifle Joint|Stifle Joint]]'''

* Like the horse the cow has three patellar ligaments; the '''middle patellar ligament''', the '''lateral patellar ligament''' and the '''medial patellar ligament'''.
* The '''middle patellar ligament''' connects the the cranial aspect of the [[Hindlimb - Anatomy & Physiology#Patella|patella]] apex to the tibial tuberosity. It has one associated bursae; one between the ligament and the groove on the tibial tuberosity. It is palpable just proximal to the tibial plateau.
* The '''medial patellar ligament''' connects the parapatellar fibrocartilage to the medial aspect of the tibial tuberosity.
* The '''lateral patellar ligament''' the cranio-lateral aspect of the [[Hindlimb - Anatomy & Physiology#Patella|patella]] to the lateral aspect of the tibial tuberosity.
* The medial and lateral femorotibial joint capsules communicate and the medial femorotibial communicates with the femoropatellar.

'''[[Hindlimb - Anatomy & Physiology#Tarsal Joint/Hock|Tarsal Joint/Hock]]'''

* The cow has some degree of flexion and extension in its proximal intertarsal joint.
* Like the dog the cow has an extra branch to its '''short medial collateral ligament''' that extends to the medial metatarsal bones.

===Musculature===

'''[[Hindlimb - Anatomy & Physiology#Muscles of the Stifle|Muscles of the Stifle]]'''

'''[[Muscles of the Bovine Crus - Anatomy & Physiology|Muscles of the Bovine Crus]]'''

==Vasculature of the Hindlimb==

'''[[Arteries of the Hindlimb - Anatomy & Physiology#Arteries of the Hindlimb|Arteries of the Hindlimb]]'''

* The essential difference between the bovine arterial system of the hindlimb and that of the dog is the supply to the distal hindlimb.
* Unlike horses and dogs the '''saphenous artery''' doesn't have cranial and caudal branches. Instead it continues down the plantar aspect of the foot and splits into the medial and lateral plantar digital arteries.
* The '''dorsal metatarsal artery III''' sits in the groove between metatarsal III andd IV and becomes the '''dorsal common digital artery III''' near the fetlock.
* An '''interdigital artery''' exists that connects the dorsal common digital artery III and the plantar common digital artery III by passing through the interdigital space.
* There are '''axial and abaxial digits''' that run on their respective sides of the digits.

'''[[Veins of the Hindlimb - Anatomy & Physiology|Veins of the Hindlimb]]'''

'''[[Lymphatics of the Hindlimb - Anatomy & Physiology|Lymphatics of the Hindlimb]]'''

==Webinars==
<rss max="10" highlight="none">https://www.thewebinarvet.com/orthopaedics/webinars/feed</rss>

[[Category:Musculoskeletal System - Anatomy & Physiology]][[Category:Musculoskeletal Anatomy - Cattle]]

Nematode Structure and Function

2022-10-27T19:38:54Z

Roytwv:

{{OpenPagesTop}}
==Overview==
The structure of a nematode is intimately related to its function and its life cycle. Although there are common traits throughout the phylum there is also great diversity allowing each species to occupy a niche in which it may thrive.

==Body Structure==
The nematode body is cylindrical, elongated and smooth with no limbs protruding, such as is seen in the common garden worm though generally on a smaller scale. The body is contained within a tough elastic '''cuticle''' which in many species forms elaborate structures useful for identification. The presence of a cuticle is similar to the structure of [[:Category:Arthropods|arthropods]], however unlike them the nematode cuticle is not chitinous but is comprised mainly of collagens. The cuticle is non-living, produced by cells of the epidermis in most of the worm, allowing it to grown between moults of the worm without the need for shedding, although this does occur a number of times during the development of most worms. It is permeable to allow ions and water to pass through and therefore plays a key role in maintaining the hydrostatic pressure, which in most nematodes is relatively high inside the worm. The cuticle also acts as an anchoring point during locomotion as a skeleton does in mammalian species.

Morphological differences in the cuticle are regularly used to identify different species of nematodes, though the functions of these are not all completely understood.
*'''Annulations''' - Transverse lines in cuticle, possibly used as anchoring points in locomotion
*'''Longitudinal Ridges''' - also known as 'synlophe', seen in some Trichostrongylidea species such as ''[[Nematodirus]]''.
*'''Alae''' or '''wings''' - Projections of the outer cuticle layer. Can appear either just at the anterior or posterior or along the entire length of the worm. In [[Bursate Nematodes|bursate]] males posterior alae for part of the copulatory bursa.
*'''Spines''' - Protrusions of the cuticle on the surface of the nematode. Function unknown, could be in self defense or attachment to host.
*'''Inflations''' - Vesicle like swellings of the cuticle function unknown. Found in ''[[Oesophagostomum]]'' species.

==Locomotion==
[[Image:Nematode muscle.gif|thumb|right|200px|Diagram showing nematode muscle arrangement and innervation - BIODIDAC]]
Locomotion in nematodes involves somatic muscles that are present below the cuticle and hypodermis. They are attached to the hypodermis and separated into four sections by hypodermal cords. They are obliquely striated unlike mammalian muscles and have dense bodies as opposed to Z disks. Two types of muscle arrangement occur in nematodes, platymyarian in small worms and coelomyarian in larger worms. During locomotion the muscles are used to apply pressure laterally to the cuticle, this pressure is opposed by the high hydrostatic pressure of the coelom and causes dorso-ventral bending. These muscular contractions cause the nematode moves in a 'sinusoidal' manner.

==Nervous System==
Knowledge of the nervous system employed by nematodes has enabled the development of many anti-parasitic drugs as they work to disrupt this system. There is a neural ring around the pharynx of the nematode containing 4 ganglia, sensory and motor neurones extend to the anterior of the worm to innervate the pharynx. One ventral and one dorsal nerve cord extend distally from the neural ring run down the length of the worm with the hypodermal cord, these are responsible for innervating body wall muscles.

The muscles involved in feeding respond to a range of [[Neurotransmitters - Anatomy & Physiology|neurotransmitters]] that can either be excitatory or inhibitory. The '''5-HT''' neurotransmitter, also known as serotonin, stimulates rhythmical contractions of pharyngeal muscles required to generate the pharyngeal pumping action. The rate of pumping in the pharynx is regulated by the neurotransmitter '''Acetylcholine''' (ACh). The pharyngeal muscles are inhibited by the actions of '''Glutamate''' and '''GABA''' which bind to post synaptic receptors and cause hyperpolarisation of the post synaptic membrane. The hyperpolarisation results in inhibition of the muscle actions as a greater stimulatory effect is required to overcome this and depolarise the cell.

In locomotion both inhibitory and excitatory neurones play an important role in contracting and relaxing muscles to allow sinusoidal movement. '''Acetylcholine''' is responsible for excitation of muscles, leading to contraction. Contraction of the ventral body wall muscles causes bending of a section of the nematode dorsally, to allow this the muscles on the dorsal wall opposite must be relaxed. Relaxation of body wall muscles is brought about by the release of '''GABA''' from the pre-synaptic membrane, this prevent contraction and allows the body wall to bend. In this way the two neurotransmitters work as an antagonistic pair to bring about sinusoidal locomotion.

==Feeding and Digestion==
[[Image:Nematode pharynx.jpg|thumb|right|200px|Diagram showing cross-section of a nematode at the level of the pharynx - BIODIDAC]]
The pharynx is situated at the anterior end of the nematode and is used in feeding, often being embedded into the epidermis or blood vessels of the worms predilection site. There are a number of different mechanisms by which nematodes feed. Some nematodes will feed on the ingesta of the host or its secretions, whilst others will suck a 'plug' of mucosa into their buccal capsules, generating an ulcer. One of the most damaging ways in which nematodes feed is by burying deep into the mucosa and feeding directly on the hosts blood. The pharynx may be specialized depending on the predeliction site and food type that the nematode requires, many blood feeders have teeth or plates used for attachment. The pharynx has a radial muscle that is used in pumping food into the intestines. The food enters the buccal capsule the size and shape of which is characteristic in some species of nematode. Due to the high pressure levels in the nematode body cavity there is a one way valve between the oesophagus and intestines and food is pushed through this by peristaltic action of radial oesophageal muscles.

The intestines of nematodes are simple tubes, only a single cell thick. The number of cells can range from 10's to one million and can be used as an identifying feature in some species. The cells are lined with microvilli, similarly to those in the mammalian gut, which are used to provide surface area for the absorption of nutrients. Lipid globules are also stored within the intestinal lumen and can occupy up to 50% of its volume. Digestion occurs rapidly and faeces is expelled under pressure from the posterior of the nematode.

==Reproduction==
[[Image:Nematode copulation.jpg|thumb|right|200px|Diagram showing nematode copulation - BIODIDAC]]
The reproductive systems are major organs of the nematodes and can occupy a large portion of the body cavity in males and females. There are many morphological and physiological differences between the species and so they are separated here.

====Males====
Males are either monorchic (most secernentea) or diorchic (most Adenophera), with regards to the number of testis present. The testis are tubular structures lined with epithelium and glandular tissue, sperm are produced at the end and mature as they migrate towards the shared opening of the cloaca. Many males have paired chitinous protrusion from the cloaca known as '''spicules''', these are used for attaching to a female during copulation. The spicules are easily seen under a microscope due to their chitinous structure and their position and shape may be used as an identifying feature. Sperm are ejaculated from the cloaca around the spicule, rather than through it. The sperm produced by nematodes is amoeboid and is very motile, employing the same locomotion mechanism as seen in amoeboid species.

One of the most distinctive features of some male nematodes is the presence of a copulatory bursa, seen in nematodes of the order Strongylida. Nematodes with a copulatory bursa are known as [[Bursate Nematodes|'''Bursate''']], whilst those without are [[:Category:Non-Bursate Nematodes|'''non-bursate''']]. This bursa is at the posterior end of the nematode and is formed from alae with laeral rays that are used for grasping onto the body of the female during copulation.

====Females====
[[Image:Female nematode xsection.jpg|thumb|right|200px|Cross section of a female nematode showing the position of the uterus - I. Livingsotne - BIODIDAC]]
Female nematodes usually have a single genital pore through which sperm may enter the uterus and oviduct, this pore is also referred to as a vulva and may be covered by a vulval flap. The uterus may take many forms form being short and straight, long with a single bend or a coiled form. Eggs produced in the ovaries populate the oviducts and uterus and may be released as embryonated or non embroynated eggs once fertilisation has occured. A small muscular organ exists at the vulval opening of some species known as the '''ovijector''', this organ aids in the expulsion of eggs from the vulva. Unlike in male nematodes the end of the female is usually blunt ended with the anus being positioned proximally on the body wall.

{{Learning
|flashcards = [[Nematode_Flashcards|Nematode Flashcards]]
|literature search = [http://www.cabdirect.org/search.html?q=de%3A%28nematodes%29+AND+%28title%3A%28structure%29+OR+title%3A%28function%29%29&fq=sc%3A%22ve%22 Nematode Structure and/or Function publications]
}}

==References==
*Nottingham Vet School 2nd Year notes

*http://entomology.ucdavis.edu/courses/ent156/securedocs/lectures/ENT156T3.pdf

==Webinars==
<rss max="10" highlight="none">https://www.thewebinarvet.com/parasitology/webinars/feed</rss>

[[Category:Nematodes|A]]
[[Category:To_Do_-_Parasites]]

[[Category:Expert_Review]]

Nematode Structure and Function

2022-10-27T19:38:11Z

Roytwv:

{{OpenPagesTop}}
==Overview==
The structure of a nematode is intimately related to its function and its life cycle. Although there are common traits throughout the phylum there is also great diversity allowing each species to occupy a niche in which it may thrive.

==Body Structure==
The nematode body is cylindrical, elongated and smooth with no limbs protruding, such as is seen in the common garden worm though generally on a smaller scale. The body is contained within a tough elastic '''cuticle''' which in many species forms elaborate structures useful for identification. The presence of a cuticle is similar to the structure of [[:Category:Arthropods|arthropods]], however unlike them the nematode cuticle is not chitinous but is comprised mainly of collagens. The cuticle is non-living, produced by cells of the epidermis in most of the worm, allowing it to grown between moults of the worm without the need for shedding, although this does occur a number of times during the development of most worms. It is permeable to allow ions and water to pass through and therefore plays a key role in maintaining the hydrostatic pressure, which in most nematodes is relatively high inside the worm. The cuticle also acts as an anchoring point during locomotion as a skeleton does in mammalian species.

Morphological differences in the cuticle are regularly used to identify different species of nematodes, though the functions of these are not all completely understood.
*'''Annulations''' - Transverse lines in cuticle, possibly used as anchoring points in locomotion
*'''Longitudinal Ridges''' - also known as 'synlophe', seen in some Trichostrongylidea species such as ''[[Nematodirus]]''.
*'''Alae''' or '''wings''' - Projections of the outer cuticle layer. Can appear either just at the anterior or posterior or along the entire length of the worm. In [[Bursate Nematodes|bursate]] males posterior alae for part of the copulatory bursa.
*'''Spines''' - Protrusions of the cuticle on the surface of the nematode. Function unknown, could be in self defense or attachment to host.
*'''Inflations''' - Vesicle like swellings of the cuticle function unknown. Found in ''[[Oesophagostomum]]'' species.

==Locomotion==
[[Image:Nematode muscle.gif|thumb|right|200px|Diagram showing nematode muscle arrangement and innervation - BIODIDAC]]
Locomotion in nematodes involves somatic muscles that are present below the cuticle and hypodermis. They are attached to the hypodermis and separated into four sections by hypodermal cords. They are obliquely striated unlike mammalian muscles and have dense bodies as opposed to Z disks. Two types of muscle arrangement occur in nematodes, platymyarian in small worms and coelomyarian in larger worms. During locomotion the muscles are used to apply pressure laterally to the cuticle, this pressure is opposed by the high hydrostatic pressure of the coelom and causes dorso-ventral bending. These muscular contractions cause the nematode moves in a 'sinusoidal' manner.

==Nervous System==
Knowledge of the nervous system employed by nematodes has enabled the development of many anti-parasitic drugs as they work to disrupt this system. There is a neural ring around the pharynx of the nematode containing 4 ganglia, sensory and motor neurones extend to the anterior of the worm to innervate the pharynx. One ventral and one dorsal nerve cord extend distally from the neural ring run down the length of the worm with the hypodermal cord, these are responsible for innervating body wall muscles.

The muscles involved in feeding respond to a range of [[Neurotransmitters - Anatomy & Physiology|neurotransmitters]] that can either be excitatory or inhibitory. The '''5-HT''' neurotransmitter, also known as serotonin, stimulates rhythmical contractions of pharyngeal muscles required to generate the pharyngeal pumping action. The rate of pumping in the pharynx is regulated by the neurotransmitter '''Acetylcholine''' (ACh). The pharyngeal muscles are inhibited by the actions of '''Glutamate''' and '''GABA''' which bind to post synaptic receptors and cause hyperpolarisation of the post synaptic membrane. The hyperpolarisation results in inhibition of the muscle actions as a greater stimulatory effect is required to overcome this and depolarise the cell.

In locomotion both inhibitory and excitatory neurones play an important role in contracting and relaxing muscles to allow sinusoidal movement. '''Acetylcholine''' is responsible for excitation of muscles, leading to contraction. Contraction of the ventral body wall muscles causes bending of a section of the nematode dorsally, to allow this the muscles on the dorsal wall opposite must be relaxed. Relaxation of body wall muscles is brought about by the release of '''GABA''' from the pre-synaptic membrane, this prevent contraction and allows the body wall to bend. In this way the two neurotransmitters work as an antagonistic pair to bring about sinusoidal locomotion.

==Feeding and Digestion==
[[Image:Nematode pharynx.jpg|thumb|right|200px|Diagram showing cross-section of a nematode at the level of the pharynx - BIODIDAC]]
The pharynx is situated at the anterior end of the nematode and is used in feeding, often being embedded into the epidermis or blood vessels of the worms predilection site. There are a number of different mechanisms by which nematodes feed. Some nematodes will feed on the ingesta of the host or its secretions, whilst others will suck a 'plug' of mucosa into their buccal capsules, generating an ulcer. One of the most damaging ways in which nematodes feed is by burying deep into the mucosa and feeding directly on the hosts blood. The pharynx may be specialized depending on the predeliction site and food type that the nematode requires, many blood feeders have teeth or plates used for attachment. The pharynx has a radial muscle that is used in pumping food into the intestines. The food enters the buccal capsule the size and shape of which is characteristic in some species of nematode. Due to the high pressure levels in the nematode body cavity there is a one way valve between the oesophagus and intestines and food is pushed through this by peristaltic action of radial oesophageal muscles.

The intestines of nematodes are simple tubes, only a single cell thick. The number of cells can range from 10's to one million and can be used as an identifying feature in some species. The cells are lined with microvilli, similarly to those in the mammalian gut, which are used to provide surface area for the absorption of nutrients. Lipid globules are also stored within the intestinal lumen and can occupy up to 50% of its volume. Digestion occurs rapidly and faeces is expelled under pressure from the posterior of the nematode.

==Reproduction==
[[Image:Nematode copulation.jpg|thumb|right|200px|Diagram showing nematode copulation - BIODIDAC]]
The reproductive systems are major organs of the nematodes and can occupy a large portion of the body cavity in males and females. There are many morphological and physiological differences between the species and so they are separated here.

====Males====
Males are either monorchic (most secernentea) or diorchic (most Adenophera), with regards to the number of testis present. The testis are tubular structures lined with epithelium and glandular tissue, sperm are produced at the end and mature as they migrate towards the shared opening of the cloaca. Many males have paired chitinous protrusion from the cloaca known as '''spicules''', these are used for attaching to a female during copulation. The spicules are easily seen under a microscope due to their chitinous structure and their position and shape may be used as an identifying feature. Sperm are ejaculated from the cloaca around the spicule, rather than through it. The sperm produced by nematodes is amoeboid and is very motile, employing the same locomotion mechanism as seen in amoeboid species.

One of the most distinctive features of some male nematodes is the presence of a copulatory bursa, seen in nematodes of the order Strongylida. Nematodes with a copulatory bursa are known as [[Bursate Nematodes|'''Bursate''']], whilst those without are [[:Category:Non-Bursate Nematodes|'''non-bursate''']]. This bursa is at the posterior end of the nematode and is formed from alae with laeral rays that are used for grasping onto the body of the female during copulation.

====Females====
[[Image:Female nematode xsection.jpg|thumb|right|200px|Cross section of a female nematode showing the position of the uterus - I. Livingsotne - BIODIDAC]]
Female nematodes usually have a single genital pore through which sperm may enter the uterus and oviduct, this pore is also referred to as a vulva and may be covered by a vulval flap. The uterus may take many forms form being short and straight, long with a single bend or a coiled form. Eggs produced in the ovaries populate the oviducts and uterus and may be released as embryonated or non embroynated eggs once fertilisation has occured. A small muscular organ exists at the vulval opening of some species known as the '''ovijector''', this organ aids in the expulsion of eggs from the vulva. Unlike in male nematodes the end of the female is usually blunt ended with the anus being positioned proximally on the body wall.

{{Learning
|flashcards = [[Nematode_Flashcards|Nematode Flashcards]]
|literature search = [http://www.cabdirect.org/search.html?q=de%3A%28nematodes%29+AND+%28title%3A%28structure%29+OR+title%3A%28function%29%29&fq=sc%3A%22ve%22 Nematode Structure and/or Function publications]
}}

==References==
*Nottingham Vet School 2nd Year notes

*http://entomology.ucdavis.edu/courses/ent156/securedocs/lectures/ENT156T3.pdf

==Webinars==
<rss max="10" highlight="none">https://www.thewebinarvet.com/orthopaedics/webinars/feed</rss>

[[Category:Nematodes|A]]
[[Category:To_Do_-_Parasites]]

[[Category:Expert_Review]]

Oesophagus - Anatomy & Physiology

2022-10-27T19:37:39Z

Roytwv:

{{OpenPagesTop}}
==Introduction==

The oesophagus (or gullet) is a muscular tube which transports food from the [[Pharynx - Anatomy & Physiology|pharynx]] to the [[Monogastric Stomach - Anatomy & Physiology|stomach]]. A bolus of food is passed down the oesophagus by peristalsis. The oesophagus is divided into cervical, thoracic and abdominal sections.

==Structure and Function==
[[Image:Oesophagus anatomy.jpg|thumb|right|250px|Oesophagus Anatomy - Copyright RVC 2008]]
The oesophagus begins dorsal to the '''cricoid cartilage''' of the [[Larynx - Anatomy & Physiology|larynx]]. It follows the trachea down the neck, first on the left and then medially once in thorax in the mediastinum. It passes over the [[Heart - Anatomy & Physiology|heart]] then through the oesophageal hiatus of the diaphragm. It passes over the dorsal border of the [[Liver - Anatomy & Physiology|liver]] then joins the [[Monogastric Stomach - Anatomy & Physiology|stomach]] at the cardia. The cervical section is accompanied by the common carotid artery, the vagosympathetic trunk and the recurrent laryngeal nerves. The thoracic section is accompanied by the right and left vagus nerves ([[Cranial Nerves - Anatomy & Physiology|CN X]]).

There are different proportions of striated muscle across the species;
:Dog and ruminant = 100%
:Cat = 80% (rostral)
:Horse = 65% (rostral)
:Pig = 33% (rostral)

==Histology==
[[Image:Oesophagus Histology.jpg|thumb|right|250px|Oesophagus Histology (Rat) - Copyright RVC 2008]]
The oesophagus has a '''stratified squamous epithelium'''. It has mucosal folds present for distension. The degree of keratinisation of the oesophagus depends on the animal's diet.

The '''lamina propria''' of the oesophagus contains collagen and elastic fibres that are sparsely distributed. The '''lamina muscularis''' of the oesophagus is smooth or skeletal muscle, depending on the species. The inner circular layer of the '''tunica muscularis''' thickens near the gastric junction, forming a sphincter.

Whilst there are no glands present in the mucosa, there are mucous glands (tubulo-acinar) present in the submucosa.

==Innervation==

The oesophagus is innervated by the sympathetic nerves and parasympathetic supply from the vagus nerve ([[Cranial Nerves - Anatomy & Physiology|CN X]]) and recurrent laryngeal nerves. The myenteric plexus extends the length of the oesophagus.

==Species Differences==

Mucous glands are present in the horse, cats and ruminants only at the pharyngeal-oesophageal junction. Ruminants, horse and pig have stratified squamous epithelium continuing from the oesophagus into the stomach. Carnivores have an abrupt transition to columnar epithelium.

===Canine===
No keratinisation, the '''lamina muscularis''' is skeletal muscle and is present caudally (spirally aranged). The lamina muscularis is, however, absent cranially. Mucous glands are present throughout but more abundant caudally. There is a thick and strong sphincter of tunica muscularis.

===Equine===
Some keratinisation is present. It is larger, less wide and less dilatable as bovines, 50-60 inches long and having 3 parts.

===Ruminant===
Heavily keratinised.

===Porcine===
The lamina muscularis is present caudally (very thick) and absent cranially. There is some keratinisation. Mucous glands are abundant cranially but absent caudally. There is a thick and strong sphincter of tunica muscularis.

===Avian===
See [[Crop - Anatomy and Physiology|the crop]]. '''Ducks''' have an oesophangeal [[Tonsils - Anatomy & Physiology|tonsil]] present in the caudal segment of the oesophagus.

==Links==

'''Click here for information on [[:Category:Oesophagus - Pathology|Oesophagus Pathology]]'''

'''Click here for information on [[Megaoesophagus]].

{{Template:Learning
|flashcards = [[Oesophagus - Anatomy & Physiology - Flashcards|Oesophagus flashcards]]
|powerpoints = [[Gastrointestinal Tract Histology resource|Histology of the oesophagus - see part 1]]
|Vetstream = [https://www.vetstream.com/canis/search?s=oesophagus Clinical approach to oesophageal diseases]
}}

==Webinars==
<rss max="10" highlight="none">https://www.thewebinarvet.com/gastroenterology-and-nutrition/webinars/feed</rss>

[[Category:Alimentary System - Anatomy & Physiology]]
[[Category:Oesophagus]]
[[Category:A&P Done]]

Oesophagus - Anatomy & Physiology

2022-10-27T19:37:04Z

Roytwv:

{{OpenPagesTop}}
==Introduction==

The oesophagus (or gullet) is a muscular tube which transports food from the [[Pharynx - Anatomy & Physiology|pharynx]] to the [[Monogastric Stomach - Anatomy & Physiology|stomach]]. A bolus of food is passed down the oesophagus by peristalsis. The oesophagus is divided into cervical, thoracic and abdominal sections.

==Structure and Function==
[[Image:Oesophagus anatomy.jpg|thumb|right|250px|Oesophagus Anatomy - Copyright RVC 2008]]
The oesophagus begins dorsal to the '''cricoid cartilage''' of the [[Larynx - Anatomy & Physiology|larynx]]. It follows the trachea down the neck, first on the left and then medially once in thorax in the mediastinum. It passes over the [[Heart - Anatomy & Physiology|heart]] then through the oesophageal hiatus of the diaphragm. It passes over the dorsal border of the [[Liver - Anatomy & Physiology|liver]] then joins the [[Monogastric Stomach - Anatomy & Physiology|stomach]] at the cardia. The cervical section is accompanied by the common carotid artery, the vagosympathetic trunk and the recurrent laryngeal nerves. The thoracic section is accompanied by the right and left vagus nerves ([[Cranial Nerves - Anatomy & Physiology|CN X]]).

There are different proportions of striated muscle across the species;
:Dog and ruminant = 100%
:Cat = 80% (rostral)
:Horse = 65% (rostral)
:Pig = 33% (rostral)

==Histology==
[[Image:Oesophagus Histology.jpg|thumb|right|250px|Oesophagus Histology (Rat) - Copyright RVC 2008]]
The oesophagus has a '''stratified squamous epithelium'''. It has mucosal folds present for distension. The degree of keratinisation of the oesophagus depends on the animal's diet.

The '''lamina propria''' of the oesophagus contains collagen and elastic fibres that are sparsely distributed. The '''lamina muscularis''' of the oesophagus is smooth or skeletal muscle, depending on the species. The inner circular layer of the '''tunica muscularis''' thickens near the gastric junction, forming a sphincter.

Whilst there are no glands present in the mucosa, there are mucous glands (tubulo-acinar) present in the submucosa.

==Innervation==

The oesophagus is innervated by the sympathetic nerves and parasympathetic supply from the vagus nerve ([[Cranial Nerves - Anatomy & Physiology|CN X]]) and recurrent laryngeal nerves. The myenteric plexus extends the length of the oesophagus.

==Species Differences==

Mucous glands are present in the horse, cats and ruminants only at the pharyngeal-oesophageal junction. Ruminants, horse and pig have stratified squamous epithelium continuing from the oesophagus into the stomach. Carnivores have an abrupt transition to columnar epithelium.

===Canine===
No keratinisation, the '''lamina muscularis''' is skeletal muscle and is present caudally (spirally aranged). The lamina muscularis is, however, absent cranially. Mucous glands are present throughout but more abundant caudally. There is a thick and strong sphincter of tunica muscularis.

===Equine===
Some keratinisation is present. It is larger, less wide and less dilatable as bovines, 50-60 inches long and having 3 parts.

===Ruminant===
Heavily keratinised.

===Porcine===
The lamina muscularis is present caudally (very thick) and absent cranially. There is some keratinisation. Mucous glands are abundant cranially but absent caudally. There is a thick and strong sphincter of tunica muscularis.

===Avian===
See [[Crop - Anatomy and Physiology|the crop]]. '''Ducks''' have an oesophangeal [[Tonsils - Anatomy & Physiology|tonsil]] present in the caudal segment of the oesophagus.

==Links==

'''Click here for information on [[:Category:Oesophagus - Pathology|Oesophagus Pathology]]'''

'''Click here for information on [[Megaoesophagus]].

{{Template:Learning
|flashcards = [[Oesophagus - Anatomy & Physiology - Flashcards|Oesophagus flashcards]]
|powerpoints = [[Gastrointestinal Tract Histology resource|Histology of the oesophagus - see part 1]]
|Vetstream = [https://www.vetstream.com/canis/search?s=oesophagus Clinical approach to oesophageal diseases]
}}
==Webinars==
<rss max="10" highlight="none">https://www.thewebinarvet.com/orthopaedics/webinars/feed</rss>
[[Category:Alimentary System - Anatomy & Physiology]]
[[Category:Oesophagus]]
[[Category:A&P Done]]

Volatile Fatty Acids

2022-10-27T19:36:04Z

Roytwv:

{{OpenPagesTop}}
==Introduction==

Microbes in the rumen ferment carbohydrates into volatile fatty acids which are absorbed through the [[Rumen - Anatomy & Physiology|rumen]] wall into the blood stream. Some of the volatile fatty acids are lost during [[Eructation|eructation]].

Volatile fatty acids are the main energy source for ruminants, providing approximately 70% of the total energy requirements. They are used primarily by the microorganisms for reproduction and growth, with the excess production being used by the ruminant itself.

The three main volatile fatty acids produced in ruminants are '''acetic acid''', '''butyric acid''' and '''propanoic acid'''.

==Acetic acid==

[[Image:VFA Graph.jpg|thumb|right|250px|VFA Graph- Copyright RVC 2008]]
50-60% of VFAs produced is acetic acid. It predominates on a high roughage diet and is a precursor for mammalian milk fat. Some is also used for muscle metabolism and body fat. The molecular formula is, '''CH3.COOH'''.

==Propanoic Acid==

12-18% of VFAs produced is propanoic acid. It predominates on a high concentrate diet and provides energy via the conversion of blood glucose in the [[Liver - Anatomy & Physiology|liver]]. It is used in lactose (milk sugar) synthesis. The molecular formula is, '''CH3.CH2.COOH'''.

==Butyric Acid==

18-20% of VFAs produced is butyric acid. It provides energy to the [[Rumen - Anatomy & Physiology|rumen]] wall and is used in milk fat synthesis and for body fat, when excess energy is present in the diet. It doesn't vary in proportion to other volatile fatty acids, therefore has little influence in milk fat content. The molecular formula is, '''CH3.CH2.CH2.COOH'''.

==Links==

Click here for more information on [[Rumenal Acidosis|acidosis]].

{{Learning
|flashcards = [[Rumen Flashcards]]
}}

==Webinars==
<rss max="10" highlight="obesity nutrition eat">https://www.thewebinarvet.com/gastroenterology-and-nutrition/webinars/feed</rss>
[[Category:Stomach - Anatomy & Physiology]]

[[Category:A&P Done]]

Bovine Forelimb - Anatomy & Physiology

2022-10-27T19:34:48Z

Roytwv:

{{OpenPagesTop}}
==Structures of the Proximal Forelimb and Shoulder==

===Scapula===

The ox possesses a small '''tuber scapular''', it has an '''acromion''' present and has extensive scapular cartilage.

===Humerus===

The humerus is essentially the same conformation as that of the dog.

===Radius and Ulna===

These are complete bones in the ox but are entirely fused. There is a proximal and distal '''interosseous space''' which are the only two places where the shafts are separated. The ulna's proximal end is caudal to the radius and its distal end forms the '''lateral styloid process''', distal to the radius and articulating with the ulnar carpal bone.

==Joints of the Proximal Forelimb==
===Shoulder Joint===

The joint capsule attaches a very short distance from the periphery of the articular surfaces. The '''intertubercular (bicipital) bursa''' lies between the humeral tubercles cushioning the bicipital tendon. The bursa and tendon are held in place by the '''transverse humeral retinaculum''', running between the greater and lesser tubercles of the humerus.

===Elbow Joint===

The joint capsule attaches to the articular surface of the condyle, the periphery of the '''olecranon fossa''' and the articular cartilage of the '''trochlear notch of the ulna'''. It fuses with the collateral ligaments. Paired collateral ligaments attach the epicondyles to the tuberosities of the radius and ulna.

==Structures of the Distal Forelimb==

===Carpal bones===

The carpal bones comprise two rows:

'''Proximally''' (mediolaterally), radial, intermediate, ulnar and accessory bones.

'''Distally''', 1st is missing, 2 and 3 are fused and there is also a 4th carpal bone.

===Metacarpal bones===

These are covered in detail in the [[Bovine Lower Limb - Anatomy & Physiology|bovine lower limb]] section.

==Joints of the Distal Forelimb==
===Carpal Joint===

The carpal joint is a compound joint composed of:

1. The '''antebrachiocarpal joint''' between the radius/ulna and the proximal carpal bones.

2. The '''middle carpal joint''' between the two rows of carpal bones.

3. The '''carpometacarpal joint''' between the distal carpal bones and the proximal metacarpals.

The joint is a synovial joint, consisting of a common outer fibrous capsule and three inner synovial pouches, one for each joint. '''Collateral ligaments''' extend from the radius to the metacarpal bones on the medial and lateral aspect of the carpus. The carpal canal houses both the deep digital flexor tendon, and the deep branch of the superficial digital flexor.

==Muscles of the Forelimb==
===Extrinsic Musculature===

These muscle are responsible for joining the forelimb to the trunk, forming a synsarcosis rather than a conventional joint. Collectively, they act to transfer the weight of the body to the forelimbs as well as stabilize the scapula.

'''''Trapezius''''':
:Innervated by: Accessory n.
:Origin: mid-dorsal raphe and supraspinous ligament.
:Insertion: spine of the scapula.
:Body: two parts, cervical and thoracic separated by aponeurosis.
:Action: raises scapula against the trunk and swings cranially to advance the limb.

'''''Brachiocephalic m.''''':
:Innervated by: Accessory n.
:The two parts are separated by the clavicle, where it exists.
:Origin: occipital bone, nuchal ligament and the mastoid process.
:Insertion: deltoid tuberosity and fascia of the limb.
:Actions: advances the limb and extends the shoulder joint when limb is in motion. Draws the head and neck ventrally when the limb is fixed.

'''''Omotransversarius''''':
:Innervated by: Accessory n.
:Origin: transverse processes of the atlas.
:Insertion: acromion and spine of scapula.
:Action: advancing the limb.

'''''Latissimus dorsi''''':
:Innervated by: local branch of brachial plexus
:The broadest muscle of the back.
:Origin: thoracolumbar fascia.
:Insertion: teres tuberosity of the humerus.
:Actions: antagonist to the brachiocephalic m. The cranial fibers strap the scapula to the chest. It retracts the free limb and flexes shoulder joint. It draws the trunk forward over the fixed limb.

'''''Pectoral mm.''''':
:Innervated by: brachial plexus
:Two superficial parts, cranial and caudal, these aren't very distinct in the ox.
:Origin: cranial sternum.
:Insertion:
::cranial ('''descending'''), crest of the humerus distal to the deltoid tuberosity.
::caudal ('''transverse'''): covers elbow joint to insert on the medial fascia of the forearm.
:Action: adduct the forelimb and assist in protraction and retraction.

'''''Serratis ventralis''''':
:Innervated by: branch of the brachial plexus.
:Origin: C4 to 10th rib.
:Insertion: medial scapula and scapular cartilage.
:Action: supporting the weight of the trunk. It is reinforced by strong fascia. The cervical portion can retract the limb and the caudal portion can advance the limb.

'''''Rhomboids''''':
:Innervated by: brachial plexus
:Origin: nuchal ligament.
:Insertion: dorsal border and adjacent scapula.
:Action: retracting the limb, may also raise the limb.

===Intrinsic Musculature===
==Muscles of the Shoulder==

These muscles are grouped:

===1. Lateral===

'''''Supraspinatus''''' and '''''Infraspinatus''''':
:Innervated by: Suprascapular n. of the brachial plexus.
:Origin: the fossae of the scapula.
:Insertion: both tubercles of the humerus.
:Action: brace the shoulder.
:Clinical significance: bursa between the tendon of the infraspinatus and lateral tubercle of the humerus can be the site of inflammation.

===2. Medial===

'''''Supscapularis''''':
:Innervated by: Subscapular n. from the brachial plexus.
:Origin: Deep surface of the scapula.
:Insertion: medial tubercle of the humerus.
:Action: braces medial shoulder joint, potential adductor.

'''''Coracobrachialis''''':
:Innervated by: Musculocutaneous n. of the brachial plexus.
:Origin: medial supraglenoid tubercle.
:Insertion: proximal shaft of the humerus.
:Action: fixator.

===3. Caudal (Flexors)===

'''''Deltoids''''':
:Innervated by: Axillary n. of the brachial plexus.
:Origin: Two heads of origin; the caudal border and spine of the scapula and the acromion.
:Insertion: deltoid tuberosity on the humerus.
:Action: Flexor of Shoulder.

'''''Teres Major''''':
:Innervated by: Axillary n. of the brachial plexus.
:Origin: dorsal part of the caudal scapula.
:Insertion: teres tuberosity midway down humerus.

'''''Teres Minor''''':
:Innervated by: Axillary n. of the brachial plexus.

There are no defined extensors of the shoulder. Those involved (brachiocephalic m., biceps brachii, supraspinatus, and ascending pectorals) have other, more primary roles.

==Muscles of the Elbow==

===Extensors===

'''''Triceps brachii''''':
:Innervated by: Radial n. from the brachial plexus
:Has three heads, the medial branch is the most developed. The long head is at the caudal margin of the scapula; The lateral, medial, and accessory heads are at the shaft of the humerus.
:Insertion: olecranon, proteced by tricipital bursa against the bone and subcutaneous bursa against the skin.

'''''Tensor fasciae antebrachii''''':
:Innervated by: Radial n. from the brachial plexus.
:Overlies the triceps extending from the scapula to the olecranon.

===Flexors===

'''''Biceps brachii''''':
:Innervated by:Musculocutaneous n. from the brachial plexus.
:Origin: supraglenoid tubercle of the scapula.
:Insertion: medial tuberosity of proximal radius and adjacent ulna. It runs through the intertubercular groove of the humerus.

'''''Brachialis''''':
:Innervated by: Musculocutaneous n. from the brachial plexus.
:Origin: proximocaudal humerus.
:Insertion: spirals to insert next to biceps.

==Muscles of the Carpal and Digital Joints==

===Extensors===

All have innervation from the radial n. from the brachial plexus. They have a craniolateral position on the forearm and almost all of them originate from the lateral epicondyle of the humerus.

'''''Extensor carpi radialis'''''
:The most medial, inserts on 2nd/3rd metacarpal bone.

'''''Ulnaris lateralis'''''
:The most lateral, inserts on accessory carpal bone.

'''''Extensor carpi obliquus''''' (aka- abductor pollicis longus)
:Origin: cranial radius.
:Insertion: most medial metacarpal bone .

'''''Common Digital Extensor'''''
:Insertion: extensor process of the distal phalanx of each digit.

'''''Lateral Digital Extensor'''''
:Insertion: dorsal proximal phalanges.

'''''Medial Digital Extensor'''''
:Insertion: middle and distal phalanges.

===Flexors===

All innervated by the median or ulnar n. of the brachial plexus. Have a caudal position on the forearm and originate from the caudal medial epicondyle of the humerus.

'''''Flexor carpi radialis'''''
:The most medial, inserts on upper 2nd/3rd metacarpal bone.

'''''Flexor carpi ulnaris'''''
:The most lateral, inserts on the accessory carpal bone.

'''''Superficial Digital Flexor'''''
:Insertion: palmar surface of middle phalanges.

'''''Deep Digital Flexor'''''
:Passes through carpal canal before branching and continues to palmar distal phalanges.

'''''Interosseus muscles'''''
:This is covered in more detail in the [[Bovine Lower Limb - Anatomy & Physiology|bovine lower limb]] section.

==Vasculature of the Forelimb==

Click here for information on:

'''[[Arteries of the Forelimb - Anatomy & Physiology|Arteries of the Forelimb]]'''

'''[[Veins of the Forelimb - Anatomy & Physiology|Veins of the Forelimb]]'''

'''[[Lymphatics of the Forelimb - Anatomy & Physiology|Lymphatics of the Forelimb]]'''

==Webinars==
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[[Category:Musculoskeletal System - Anatomy & Physiology]][[Category:Musculoskeletal Anatomy - Cattle]]
[[Category:A&P Done]]

Bovine Forelimb - Anatomy & Physiology

2022-10-27T19:34:13Z

Roytwv:

{{OpenPagesTop}}
==Structures of the Proximal Forelimb and Shoulder==

===Scapula===

The ox possesses a small '''tuber scapular''', it has an '''acromion''' present and has extensive scapular cartilage.

===Humerus===

The humerus is essentially the same conformation as that of the dog.

===Radius and Ulna===

These are complete bones in the ox but are entirely fused. There is a proximal and distal '''interosseous space''' which are the only two places where the shafts are separated. The ulna's proximal end is caudal to the radius and its distal end forms the '''lateral styloid process''', distal to the radius and articulating with the ulnar carpal bone.

==Joints of the Proximal Forelimb==
===Shoulder Joint===

The joint capsule attaches a very short distance from the periphery of the articular surfaces. The '''intertubercular (bicipital) bursa''' lies between the humeral tubercles cushioning the bicipital tendon. The bursa and tendon are held in place by the '''transverse humeral retinaculum''', running between the greater and lesser tubercles of the humerus.

===Elbow Joint===

The joint capsule attaches to the articular surface of the condyle, the periphery of the '''olecranon fossa''' and the articular cartilage of the '''trochlear notch of the ulna'''. It fuses with the collateral ligaments. Paired collateral ligaments attach the epicondyles to the tuberosities of the radius and ulna.

==Structures of the Distal Forelimb==

===Carpal bones===

The carpal bones comprise two rows:

'''Proximally''' (mediolaterally), radial, intermediate, ulnar and accessory bones.

'''Distally''', 1st is missing, 2 and 3 are fused and there is also a 4th carpal bone.

===Metacarpal bones===

These are covered in detail in the [[Bovine Lower Limb - Anatomy & Physiology|bovine lower limb]] section.

==Joints of the Distal Forelimb==
===Carpal Joint===

The carpal joint is a compound joint composed of:

1. The '''antebrachiocarpal joint''' between the radius/ulna and the proximal carpal bones.

2. The '''middle carpal joint''' between the two rows of carpal bones.

3. The '''carpometacarpal joint''' between the distal carpal bones and the proximal metacarpals.

The joint is a synovial joint, consisting of a common outer fibrous capsule and three inner synovial pouches, one for each joint. '''Collateral ligaments''' extend from the radius to the metacarpal bones on the medial and lateral aspect of the carpus. The carpal canal houses both the deep digital flexor tendon, and the deep branch of the superficial digital flexor.

==Muscles of the Forelimb==
===Extrinsic Musculature===

These muscle are responsible for joining the forelimb to the trunk, forming a synsarcosis rather than a conventional joint. Collectively, they act to transfer the weight of the body to the forelimbs as well as stabilize the scapula.

'''''Trapezius''''':
:Innervated by: Accessory n.
:Origin: mid-dorsal raphe and supraspinous ligament.
:Insertion: spine of the scapula.
:Body: two parts, cervical and thoracic separated by aponeurosis.
:Action: raises scapula against the trunk and swings cranially to advance the limb.

'''''Brachiocephalic m.''''':
:Innervated by: Accessory n.
:The two parts are separated by the clavicle, where it exists.
:Origin: occipital bone, nuchal ligament and the mastoid process.
:Insertion: deltoid tuberosity and fascia of the limb.
:Actions: advances the limb and extends the shoulder joint when limb is in motion. Draws the head and neck ventrally when the limb is fixed.

'''''Omotransversarius''''':
:Innervated by: Accessory n.
:Origin: transverse processes of the atlas.
:Insertion: acromion and spine of scapula.
:Action: advancing the limb.

'''''Latissimus dorsi''''':
:Innervated by: local branch of brachial plexus
:The broadest muscle of the back.
:Origin: thoracolumbar fascia.
:Insertion: teres tuberosity of the humerus.
:Actions: antagonist to the brachiocephalic m. The cranial fibers strap the scapula to the chest. It retracts the free limb and flexes shoulder joint. It draws the trunk forward over the fixed limb.

'''''Pectoral mm.''''':
:Innervated by: brachial plexus
:Two superficial parts, cranial and caudal, these aren't very distinct in the ox.
:Origin: cranial sternum.
:Insertion:
::cranial ('''descending'''), crest of the humerus distal to the deltoid tuberosity.
::caudal ('''transverse'''): covers elbow joint to insert on the medial fascia of the forearm.
:Action: adduct the forelimb and assist in protraction and retraction.

'''''Serratis ventralis''''':
:Innervated by: branch of the brachial plexus.
:Origin: C4 to 10th rib.
:Insertion: medial scapula and scapular cartilage.
:Action: supporting the weight of the trunk. It is reinforced by strong fascia. The cervical portion can retract the limb and the caudal portion can advance the limb.

'''''Rhomboids''''':
:Innervated by: brachial plexus
:Origin: nuchal ligament.
:Insertion: dorsal border and adjacent scapula.
:Action: retracting the limb, may also raise the limb.

===Intrinsic Musculature===
==Muscles of the Shoulder==

These muscles are grouped:

===1. Lateral===

'''''Supraspinatus''''' and '''''Infraspinatus''''':
:Innervated by: Suprascapular n. of the brachial plexus.
:Origin: the fossae of the scapula.
:Insertion: both tubercles of the humerus.
:Action: brace the shoulder.
:Clinical significance: bursa between the tendon of the infraspinatus and lateral tubercle of the humerus can be the site of inflammation.

===2. Medial===

'''''Supscapularis''''':
:Innervated by: Subscapular n. from the brachial plexus.
:Origin: Deep surface of the scapula.
:Insertion: medial tubercle of the humerus.
:Action: braces medial shoulder joint, potential adductor.

'''''Coracobrachialis''''':
:Innervated by: Musculocutaneous n. of the brachial plexus.
:Origin: medial supraglenoid tubercle.
:Insertion: proximal shaft of the humerus.
:Action: fixator.

===3. Caudal (Flexors)===

'''''Deltoids''''':
:Innervated by: Axillary n. of the brachial plexus.
:Origin: Two heads of origin; the caudal border and spine of the scapula and the acromion.
:Insertion: deltoid tuberosity on the humerus.
:Action: Flexor of Shoulder.

'''''Teres Major''''':
:Innervated by: Axillary n. of the brachial plexus.
:Origin: dorsal part of the caudal scapula.
:Insertion: teres tuberosity midway down humerus.

'''''Teres Minor''''':
:Innervated by: Axillary n. of the brachial plexus.

There are no defined extensors of the shoulder. Those involved (brachiocephalic m., biceps brachii, supraspinatus, and ascending pectorals) have other, more primary roles.

==Muscles of the Elbow==

===Extensors===

'''''Triceps brachii''''':
:Innervated by: Radial n. from the brachial plexus
:Has three heads, the medial branch is the most developed. The long head is at the caudal margin of the scapula; The lateral, medial, and accessory heads are at the shaft of the humerus.
:Insertion: olecranon, proteced by tricipital bursa against the bone and subcutaneous bursa against the skin.

'''''Tensor fasciae antebrachii''''':
:Innervated by: Radial n. from the brachial plexus.
:Overlies the triceps extending from the scapula to the olecranon.

===Flexors===

'''''Biceps brachii''''':
:Innervated by:Musculocutaneous n. from the brachial plexus.
:Origin: supraglenoid tubercle of the scapula.
:Insertion: medial tuberosity of proximal radius and adjacent ulna. It runs through the intertubercular groove of the humerus.

'''''Brachialis''''':
:Innervated by: Musculocutaneous n. from the brachial plexus.
:Origin: proximocaudal humerus.
:Insertion: spirals to insert next to biceps.

==Muscles of the Carpal and Digital Joints==

===Extensors===

All have innervation from the radial n. from the brachial plexus. They have a craniolateral position on the forearm and almost all of them originate from the lateral epicondyle of the humerus.

'''''Extensor carpi radialis'''''
:The most medial, inserts on 2nd/3rd metacarpal bone.

'''''Ulnaris lateralis'''''
:The most lateral, inserts on accessory carpal bone.

'''''Extensor carpi obliquus''''' (aka- abductor pollicis longus)
:Origin: cranial radius.
:Insertion: most medial metacarpal bone .

'''''Common Digital Extensor'''''
:Insertion: extensor process of the distal phalanx of each digit.

'''''Lateral Digital Extensor'''''
:Insertion: dorsal proximal phalanges.

'''''Medial Digital Extensor'''''
:Insertion: middle and distal phalanges.

===Flexors===

All innervated by the median or ulnar n. of the brachial plexus. Have a caudal position on the forearm and originate from the caudal medial epicondyle of the humerus.

'''''Flexor carpi radialis'''''
:The most medial, inserts on upper 2nd/3rd metacarpal bone.

'''''Flexor carpi ulnaris'''''
:The most lateral, inserts on the accessory carpal bone.

'''''Superficial Digital Flexor'''''
:Insertion: palmar surface of middle phalanges.

'''''Deep Digital Flexor'''''
:Passes through carpal canal before branching and continues to palmar distal phalanges.

'''''Interosseus muscles'''''
:This is covered in more detail in the [[Bovine Lower Limb - Anatomy & Physiology|bovine lower limb]] section.

==Vasculature of the Forelimb==

Click here for information on:

'''[[Arteries of the Forelimb - Anatomy & Physiology|Arteries of the Forelimb]]'''

'''[[Veins of the Forelimb - Anatomy & Physiology|Veins of the Forelimb]]'''

'''[[Lymphatics of the Forelimb - Anatomy & Physiology|Lymphatics of the Forelimb]]'''

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[[Category:Musculoskeletal System - Anatomy & Physiology]][[Category:Musculoskeletal Anatomy - Cattle]]
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Forelimb - Anatomy & Physiology

2022-10-27T19:33:04Z

Roytwv:

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==Common Structures of the Proximal Forelimb and Shoulder==
===Scapula===

The Scapula forms the basis of the shoulder region, providing points of attachment of extrinsic and intrinsic muscles. It is held in place by a synsarcosis of muscles and does not form a conventional articulation with the trunk. In ungulates, the dorsal border is extended by a scapular cartilage, which enlarges the area for muscle attachment. This ossifies with age. The bone is roughly triangular, with a prominent '''spine''' that can be palpated through the skin.
:The spine:
::defines '''infraspinous''' and '''supraspinous''' '''fossae''', inhabited by the infraspinatus and supraspinatus muscles respectively
::serves as a point of attachment for the '''trapezius''' muscle
::culminates in the '''acromion''' in all but the horse and pig.
::the cat also possesses a suprahamate process which lies proximal to the acromion and projects caudally.

Just cranial to the glenoid cavity can be seen a bony prominence called the supraglenoid tubercle which is the origin of the biceps bracii muscle

Medial muscle attachment consist mostly of the '''subscapularis''', with the '''serratus ventralis''' attaching dorsally. The Scapula articulates with the humerus at the '''glenoid cavity'''.

===Clavicle===

The Clavicle is all but absent in most domestic species, with the notable exception of the avian skeleton. In the dog and cat, a remnant of bone may remain embedded in the fibrous intersection in the brachiocephalicus muscle, which may prove misleading in radiographic images.

===Humerus===

The Humerus is the long bone of the arm, articulating with the scapula to form the shoulder and the radius and ulna to form the elbow. In situ, it lies obliquely along the ventral thorax and is more horizontal in larger species.

The head of the humerus comprises '''greater''' and '''lesser tubercles''', separated by an '''intertubercular groove''' through which runs the tendon of the '''biceps brachii'''. The shaft of the humerus takes on a characteristically twisted shape via a groove carrying the '''brachialis''' and '''radial nerve'''. Laterally, the '''deltoid tuberosity''' is palpable through the skin and connects to the head of the humerus via a ridge and merges distally with the '''crest of the humerus'''. Distally, the humerus culminates in a '''condyle''' which articulates to form the elbow.
:In large animals, it meets the radius via a '''trochlea'''
:In dogs and cats, it articulates with the ulna medially via a trochlea and the radius laterally via a '''capitulum'''
:Caudally, all species show an '''olecranon fossa''' which articulates with the '''olecranon''' of the ulna

At the distal end of the humerus a small hole may be seen connecting the olecranon fossa caudally with the radial fossa cranially. This is the supratrochlear foramen. No structures pass through it.

Medial and lateral epicondyles provide attachment for flexors and extensors of the carpus and digits.

==Joints of the Proximal Forelimb==
===Shoulder Joint===

The shoulder joint links the humerus and the scapula at the '''glenoid cavity''', which is much smaller than the head of the humerus. While structurally it is a [[Joints - Anatomy & Physiology#Types of Joints|'''ball and socket''']] joint, it functions as a [[Joints - Anatomy & Physiology#Types of Joints|'''hinge joint''']] due to extensive muscling around the articulation. The joint capsule is enlarged and extends under the tendon of the biceps, acting as a synovial sheath to protect the tendon.

It is important to distinguish the shoulder/scapulohumeral joint from the entirely muscular connection (synsarcosis) between the forelimb and the trunk. This latter connection is sometimes called the '''girdle muscles''', although this is a problematic term, because many of its constituent muscles do not attach to a limb girdle muscle. At Cambridge University, it has for some time been given the name '''omothoracic junction''', but this term has not entered common usage.

There are no true ligaments in the shoulder joint. The tendons of insertion of the supraspinatous and infraspinatous muscles cross the shoulder joint and insert laterally on the greater tubercle of the humerus. The tendon of the subscapularis inserts medially on the humerus. These act as 'ligaments' preventing dislocation of the shoulder.

===Elbow Joint===

Movement of the elbow joint is restricted to the [[Planes and Axes - Anatomy & Physiology|sagittal plane]]. It is bounded medially and laterally by collateral ligaments between the humerus and radius, caudally by the olecranon ligament between the humerus and olecranon, and further enforced by the annular radial ligament. The elbow is a compound joint including:
*The [[Joints - Anatomy & Physiology#Types of Joints|'''hinge joint''']] between the humerus and the radius and ulna.
*The [[Joints - Anatomy & Physiology#Types of Joints|'''pivot joint''']] between the radius and ulna.
*The point of the elbow, or the '''olecranon''' is formed by the anconeal process of the ulna inserting into the olecranon fossa of the humerus.

==Common Structures of the Distal Forelimb==
===Radius===

While in the human the radius and ulna are separated by an interosseus space and articulate only at their extremities, allowing for significant capability of supination and pronation, these movements are much more limited in domestic animals due to the gradual fusing of the two bones. The extreme case is exhibited by the horse.

The radius forms the shaft-like rod of the distal limb, which is bowed to varying degrees amongst species. It articulates proximally with the distal humerus, caudally with the ulna, and distally with the carpus. Medially on the distal articular process, a '''styloid process''' projects, which is mirrored laterally by the ulna.

===Ulna===

The Ulna's greatest contribution to functional anatomy is in the formation of the '''olecranon''', or the point of the elbow, which gives rise to the attachment of the '''triceps''' muscle. The olecranon articulates with the humerus via its anconeal process. The olecranon develops as an apophysis, i.e.. from a separate site of ossification. The trochlear notch on the cranial aspect of the ulna articulates with the large trochlea of the humerus which forms the main elbow joint capable of flexion and extension. Just distal to the trochlear notch, a large medial '''coronoid process''' and a smaller lateral coronoid process can be seen. Distally (where unfused), the '''lateral styloid process''' articulates with the '''ulnar carpal bone'''.

===Carpal bones===

Carpal bones comprise two rows:
*Proximally, (mediolaterally), radial, intermediate, ulnar and accessory bones. The accessory bone serves as a landmark for palpation.
*Distally, bones are numbered 1-5, though 5 is always fused with 4.

A small [[Bones - Anatomy & Physiology#Types of Bone|'''sesamoid''']] bone embedded in the medial tissues of the joint can sometimes be mistaken as a chip fracture.

===Metacarpal bones===

The number of metacarpals varies widely among species, as the demand for their function changes: '''plantigrade''', or flat-footed, animals requiring the full complement of five metacarpal bones; the number is reduced in the upright stature of '''digitigrade''' animals such as the dog and cat, and shows the extreme in '''unguligrades''' like the horse, which depends entirely on the third metacarpal bone for its stature.

Colloquially, the third metacarpal of the horse is known as the '''canon''' bone, and the vestigial 2 and 4 as '''splint bones'''

==Joints of the Distal Forelimb==
===Carpal Joint===

The carpal joint is a compound joint composed of:
*The '''antebrachiocarpal joint''' between the radius/ulna and the proximal carpal bones
*The '''middle carpal joint''' between the two rows of carpal bones
*The '''carpometacarpal joint''' between the distal carpal bones and the proximal metacarpals

The joint is a synovial joint, compring a common outer fibrous capsule and three inner synovial pouches, one for each joint. Numerous ligaments add to the stability of the joint and ensure movement is largely limited to the [[Planes and Axes - Anatomy & Physiology|sagittal plane]], although no collateral ligaments exist in the dog between the radius and the proximal metacarpals. This allows a very small amount of rotation.

===Metacarpal Joint===

The metacarpal joint is defined by the presence of palmar [[Bones - Anatomy & Physiology#Types of Bone|'''sesamoids''']], which allow the flexor tendons to pass over the sharp change in angle presented by the joint. They are paired on each digit, with the exception of the first digit where only one exists. A single '''dorsal sesamoid bone''' can also be seen in dogs in digit 2 - 5 inclusive over the same joint between the metacarpal bone and the proximal phalanx. This is not found in ungulates or in the the first digit. However another sesamoid bone exists in the tendon of the abductor pollicis longus muscle of the first digit.

==Muscles of the Forelimb==
===Extrinsic Musculature===

These muscle are responsible for joining the forelimb to the trunk, forming a synsarcosis rather than a conventional joint. Collectively, they act to transfer the weight of the body to the forelimbs as well as stabilize the scapula.

'''''Trapezius''''':
:Innervated by: Accessory n.
:Origin: mid-dorsal raphe and supraspinous ligament
:Insertion: spine of the scapula
:Body: two parts, cervical and thoracic separated by aponeurosis
:Action: raises scapula against the trunk and swings cranially to advance the limb

'''''Brachiocephalic m.''''':
:Innervated by: Accessory n.
:Two parts separated by the clavicle where it exists
:Origin: clavicle or vestigial fibrous intersection
:Insertion: several places on the head and neck
:Actions:
::advances the limb and extends the shoulder joint when limb is in motion
::draws head and neck ventrally when limb is fixed

'''''Omotransversarius''''':
:Innervated by: Accessory n.
:Origin: transverse processes of the atlas
:Insertion: acromion and adjacent scapula
:Action: advancing the limb

'''''Latissimus dorsi''''':
:Innervated by: local branch of brachial plexus
:The '''broadest muscle of the back'''
:Origin: thoracolumbar fascia
:Insertion: teres tuberosity of the humerus
:Actions:
::antagonist to the brachiocephalic m.
::cranial fibers strap scapula to the chest
::retracts free limb and flexes shoulder joint
::draws trunk forward over the fixed limb

'''''Pectoral mm.''''':
:Innervated by: brachial plexus
::superficial pectoral m. - ventral branches of cervical spinal nerves 7 and 8 (Evans and de Lahunta's Guide to the Dissection of the Dog, 8th ed.)
::deep pectoral m. - caudal pectoral nerves, cervical spinal nerve 8, and thoracic nerve 1 (Evans and de Lahunta's Guide to the Dissection of the Dog, 8th ed.)

:Two superficial parts, cranial and caudal
:Origin: cranial sternum
:Insertion:
::cranial ('''descending'''): crest of the humerus distal to the deltoid tuberosity
::caudal ('''transverse'''): covers elbow joint to insert on the medial fascia of the forearm
:Action: adduct the forelimb, assist in protraction and retraction

:One deep part ('''pectoralis profundus'''), with cranial and caudal parts
:Origin: ventral sternum and adjacent cartilage
:Insertions:
::cranial (subclavius): supraspinatus m.
::caudal (pectoralis ascendens): lesser tubercle of the humerus
:Actions:
::slinging trunk between forelimbs
::may also retract free limbs
::draw trunk forward when limb is fixed

'''''Serratis ventralis''''':
:Innervated by: branch of brachial plexus
:Origin: C4 to 10th rib
:Insertion: medial scapula and scapular cartilage
:Action:
::supporting the weight of the trunk reinforced by strong fascia
::cervical portion can retract the limb
::caudal portion can advance the limb

'''''Rhomboids''''':
:Innervated by: brachial plexus, although in some species, dorsal spinal nerves can innervate
:Origin: median connective tissue from poll to withers, lying deep to the trapezius
:Insertion: dorsal border and adjacent scapula
:Action: retracting the limb, may also raise limb

===Intrinsic Musculature===
====Muscles of the Shoulder====
These muscles are grouped:

Lateral:'''Supraspinatus ''' and '''Infraspinatus''',
:Innervated by: Suprascapular n. of the brachial plexus
:Origin: the fossae of the scapula
:Insertion: both tubercles of the humerus
:Action: brace the shoulder
:Clinical significance: bursa between the tendon of the infraspinatus and lateral tubercle of the humerus can be the site of inflammation

Medial:
'''Subscapularis''':
:Innervated by: Subscapular n. from the brachial plexus
:Origin: Deep surface of the scapula
:Insertion: medial tubercle of the humerus
:Action: braces medial shoulder joint, potential adductor

'''Coracobrachialis''':
:Innervated by: Musculocutaneous n. of the brachial plexus
:Origin: medial supraglenoid tubercle
:Insertion: proximal shaft of the humerus
:Action: fixator

Caudal (Flexors):
:Innervated by: Axillary n. of the brachial plexus
:'''Deltoids'''
::Origin: caudal border and spine of the scapula, one head in the horse and two in species with an acromion (site of second origin)
::Insertion: deltoid tuberosity on the humerus
:'''Teres Major'''
::Origin: dorsal part of the caudal scapula
::Insertion: teres tuberosity midway down humerus
:'''Teres Minor'''

There are no defined extensors of the shoulder. Those involved (brachiocephalic m., biceps brachii, supraspinatus, and ascending pectorals) have other, more primary roles.

====Muscles of the Elbow====
''Extensors'':
:Innervated by: Radial n. from the brachial plexus

:'''Triceps brachii''': Three heads, four in the dog
::Long head: caudal margin of the scapula
::Lateral, medial, and accessory heads: shaft of the humerus
::Insertion: olecranon, proteced by tricipital bursa against the bone and subcutaneous bursa against the skin

:'''Tensor fasciae antebrachii'''
::Overlies triceps extending from scapula to olecranon

:'''Anconeus'''
::Origin: distal humerus
::Insertion: lateral olecranon

''Flexors'':
:Innervated by: Musculocutaneous n. from the brachial plexus

:'''Biceps brachii'''
::Origin: supraglenoid tubercle of the scapula
::Insertion: medial tuberosity of proximal radius and adjacent ulna
::Runs through the intertubercular groove of the humerus

:'''Brachialis'''
::Origin: proximocaudal humerus
::Insertion: spirals to insert next to biceps

====Muscles of Supination and Pronation ====
''Supinators'':
:Innervated by: Radial n. from the brachial plexus

:'''Brachioradialis'''
::Origin: lateral epicondyle of the humerus
::Insertion: distal medial forearm within superficial fascia
::Prominent in the cat but nearly absent in the dog

:'''Supinator'''
::Deep to extensor muscles, passing from lateral humeral epicondyles to upper medial radius

''Pronators'':
:Innervated by: Median n. from the brachial plexus

:'''Pronator teres''': only functional in cat and dog
::Origin: medial epicondyle of the humerus
::Insertion: supinator

:'''Pronator quadratus''': only found in carnivores
::Origin: shaft of the ulna
::Insertion: shaft of the radius

====Muscles of the Carpal and Digital Joints====
''Extensors'':
:Innervated by: Radial n. from the brachial plexus
:Craniolateral position on the forearm
:Almost all originate from the lateral epicondyle of the humerus

:'''Extensor carpi radialis''': most medial, inserts on 2nd/3rd metacarpal bone

:'''Ulnaris lateralis''': most lateral, inserts on accessory carpal bone

:'''Extensor carpi obliquus''': aka '''abductor pollicis longus'''
::Origin: cranial radius
::Insertion: most medial metacarpal bone

:Last two may also serve in medial deviation of the paw

:'''Common Digital Extensor'''
::Insertion: extensor process of the distal phalanx of each digit
::Sends a medial branch to dew claw and medial digits in all but horse and cat

:'''Lateral Digital Extensor'''
::Insertion: dorsal proximal phalanx

''Flexors'':
:Innervated by: Median or Ulnar n. of the brachial plexus
:Caudal position on the forearm
:Originate from the caudal medial epicondyle of the humerus

:'''Flexor carpi radialis''': most medial, inserts on upper 2nd/3rd metacarpal bone

:'''Flexor carpi ulnaris''': most lateral, inserts on the accessory carpal bone

:'''Superficial Digital Flexor'''
::Branches according to the number of digis and inserts in proximal interphalangeal joint

:'''Deep Digital Flexor'''
::Passes through carpal canal before branching and continues to palmar distal phalanges

''Interosseus muscles''
:Support metacarpophalnageal joints
:Arise from palmar proximal metacarpal bones and insert on sesamoid bones within the joints, continued by ligaments to phalanges

==Vasculature of the Forelimb==
*'''[[Arteries of the Forelimb - Anatomy & Physiology|Arteries of the Forelimb]]'''
*'''[[Veins of the Forelimb - Anatomy & Physiology|Veins of the Forelimb]]'''
*'''[[Lymphatics of the Forelimb - Anatomy & Physiology|Lymphatics of the Forelimb]]'''

==Innervation of the Forelimb==

The nerves affecting the forelimb arise from spinal nerves C6 to T2 and pass through the '''brachial plexus'''.

'''Suprascapular Nerve'''
* Origin - cranial part of brachial plexus, C6 and C7
* Motor innervation - supraspinatus and infraspinatus
* Sensory innervation - none
* Route - out of the brachial plexus, laterally round the cranial aspect of the neck of the scapula

'''Subscapular Nerve'''
* Origin - cranial part of the brachial plexus, C6 and C7
* Motor innervation - subscapular muscle
* Sensory innervation - none
* Route - direct to muscle

'''Musculocutaneous Nerve'''
* Origin - middle part of the brachial plexus, C7 and C8 (sometimes C6)
* Motor innervation - Biceps brachii, brachialis, coracobrachialis
* Sensory innervation - dorsomedial aspect of forelimb
* Route - medial aspect of the limb, close to the median nerve

'''Axillary Nerve'''
* Origin - middle brachial plexus, C7 and C8
* Motor innervation - shoulder flexors, teres minor, deltoid
* Sensory innervation - dorso-lateral aspect of proximal limb
* Route - behind the shoulder joint

'''Radial Nerve'''
* Origin - caudal brachial plexus, C7 to T2
* Motor innervation - extensors of elbow, carpus and digits
* Sensory innervation - dog: craniolateral and medial forearm, horse: lateral forearm
* Route - through the triceps, around the humerus to the lateral aspect of the forearm

'''Median and Ulnar Nerves'''
* Origin - caudal brachial plexus, C8, T1 and T2
* Motor innervation - flexors of carpus and digits
* Sensory innervation - caudal aspect of the limb
* Route - along the medial aspect of the limb, the median forms branches to the musculocutaneous nerve

==Species Specifics==
===[[Canine Forelimb - Anatomy & Physiology|Canine Forelimb]]===
===[[Bovine Forelimb - Anatomy & Physiology|Bovine Forelimb]]===

{{Template:Learning
|OVAM = [http://www.onlineveterinaryanatomy.net/content/muscle-flashcards-forelimb-extrinsics-quicktime Muscle flashcards - extrinsic musculature of the canine forelimb]<br>[http://www.onlineveterinaryanatomy.net/content/muscle-flashcards-shoulder-quicktime Muscle flashcards - muscles of the canine shoulder]<br>[http://www.onlineveterinaryanatomy.net/content/muscle-flashcards-elbow-quicktime Muscle flashcards - muscles of the canine elbow]<br>[http://www.onlineveterinaryanatomy.net/content/muscle-flashcards-antebrachium-quicktime Muscle flashcards - muscles of canine antebrachium]
}}

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[[Category:Musculoskeletal System - Anatomy & Physiology]]
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Cranial Nerves - Anatomy & Physiology

2022-10-27T19:30:47Z

Roytwv:

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[[File:Brain human normal inferior view with labels en.svg|thumb|right|400px|Ventral brain showing labelled cranial nerves, WikiCommons]]
==Introduction==
Cranial nerves are those nerves which arise from the brain and [[Hindbrain - Anatomy & Physiology|brain stem]] rather than the spinal cord. Nerves arising from the spinal cord are the [[PNS Structure - Anatomy & Physiology|spinal nerves]]. There are 12 pairs of cranial nerves and these pairs of nerves passage through [[Skull and Facial Muscles - Anatomy & Physiology|foramina in the skull]], either individually or in groups. Cranial nerves are traditionally referred to by Roman numerals and these numerals begin cranially and run caudally.
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The most cranial nerve is the '''Olfactory nerve (I)''' which runs from the nasal cavity through to the olfactory bulb. The next most cranial is the '''Optic nerve (II)''' which runs from the eyes to the [[Forebrain - Anatomy & Physiology#Thalamus|thalamus]]. Cranial nerves III to XII all exit from the brain stem and innervate the head, neck and organs in the thorax and abdomen. In order of most cranial to caudal, these include the '''Oculomotor nerve (III)''', the '''Trochlear nerve (IV)''', the '''Trigeminal nerve (V)''', the '''Abducens nerve (VI)''', the '''Facial nerve (VII)''', the '''Vestibulocochlear nerve (VIII)''', the '''Glossopharyngeal nerve (IX)''', the '''Vagus nerve (X)''', the '''Accessory nerve (XI)''' and the '''Hypoglossal nerve (XII)'''.
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Many of the cranial nerves with nuclei within the brain stem contain sensory and motor neurone components. The sensory fibre components have their cell bodies located in ganglia outside the central nervous system and the motor fibre element have their cell bodies within the central nervous system.

==Cranial Nerve Fibre Types==
Prior to a full explanation of each cranial nerve function, physiology, anatomy and particularly composition, the numerous types of nerve fibre found in cranial nerves must be explained to ensure that the following can be better understood.

Nerve fibres can undertake numerous roles within the body and their function is dictated by what type of fibre the nerve is composed of. A classification scheme is used to describe the type of fibres found within the cranial nerves and therefore provides a better understanding of the function and composition of that particular nerve. Below is a brief outline of this nerve fibre classification.

===Afferent Fibres - Sensory===
====General Somatic Afferent (GSA)====
This type of fibre is used in the majority of basic senses including temperature, touch and [[Pain|pain]]. These fibres mainly supply sensation to various areas of the head including to the skin and face via the trigeminal nerve (cranial nerve V); to the skin of the [[Ear - Anatomy & Physiology#Outer_Ear|external ear]] via the trigeminal nerve (cranial nerve V), the facial nerve (cranial nerve VII), the glossopharyngeal nerve (cranial nerve IX) and via the vagus nerve (cranial nerve X); to the mucosae of the [[Oral Cavity Overview - Anatomy & Physiology|oral cavity]] via the trigeminal nerve (cranial nerve V) and to the [[Meninges - Anatomy & Physiology|meningies]] of the brain via the trigeminal nerve (cranial nerve V) and the vagus nerve (cranial nerve X).

:'''Skin Sensation Example'''

:''Sensory cortex —→ Thalamus —→ Trigeminal nuclei —→ Trigeminal ganglion —→ Skin etc.''

====Special Somatic Afferent (SSA)====
The special signifies that this fibre type is found in nerves related to the special senses which include [[Eye - Anatomy & Physiology#Vision|vision]] and [[Ear - Anatomy & Physiology#Function_-_Hearing|hearing]]. This therefore relates to the optic nerves (cranial nerve II) and the auditory/vestibular systems which are the vestibulocochlear nerves (cranial nerve VIII).

:'''Vision Example'''

:''Occipital cortex —→ Thalamus MGN —→ Rostral colliculus/Retinal ganglion cell —→ Bipolar cell —→ [[Eye - Anatomy & Physiology|Vision]]''

:'''Hearing Example'''

:''Temporal cortex —→ Thalamus MGN —→ Caudal colliculus and hindbrain —→ Spiral ganglion —→ [[Ear - Anatomy & Physiology|Hearing]]''

====General Visceral Afferent (GVA)====
This fibre type is commonly found in sensory nerves to organs and to sensory tissues related to chemicals. These include fibres found in the glossopharyngeal nerves (cranial nerve IX) and the vagus nerves (cranial nerve X).

:'''Organ Sensory Example'''

:''Sensory cortex —→ Thalamus —→ Cranial nerve nuculi —→ Nerve ganglion —→ Organs etc.''

====Special Visceral Afferent (SVA)====
This fibre type is found again in special sense organs related to the sensing of chemicals and therefore including [[Gustatory System - Anatomy & Physiology|taste]] and [[olfaction]]. The olfactory sense relates to the olfactory nerve (cranial nerve I) and the taste senses relate to the facial nerve (cranial nerve VII), the glossopharyngeal nerve (cranial nerve IX) and the vagus nerve (cranial nerve X). The sense of taste is performed by the gustatory organ which are cells located in gustatory papillae in the mucous membrane of the dorsal side of the tongue. Taste buds can also be found in the soft palate, pharynx, larynx, lips and cheeks.

:'''Olfaction Example'''

:''Piriform cortex —→ Olfactory tubercle —→ Olfactory Bulb —→ [[Nose - Anatomy & Physiology|Smell]]''

:'''Taste Example'''

:''Sensory cortex —→ Thalamus —→ Hindbrain (VII, IX, X) —→ Ganglion —→ [[Gustatory System - Anatomy & Physiology|Taste]]''

===Efferent Fibres - Motor===
====General Somatic Efferent (GSE)====
This type of nerve fibre is mainly found in nerves supplying [[Muscles - Anatomy & Physiology#Skeletal_Muscle|skeletal muscles]]. Motor fibres such as these undertake numerous roles within the body such as control over the external ocular muscles via the oculomotor nerve (cranial nerve III), the trochlear nerve (cranial nerve IV) and the abducent nerve (cranial nerve VI); or for example the muscles around the dorsal and ventral neck including the brachiocephalicus, trapezius, omotransversarius and the sternocephalicus which are all supplied by the accessory nerve (cranial nerve XI).

:'''Motor Nerve Innervation Example'''

:''Motor cortex —→ Motor nuculi —→ Muscle''

====General Visceral Efferent (GVE)====
This type of nerve fibre is found in nerves supplying [[Muscles - Anatomy & Physiology#Smooth_Muscle|smooth muscle]], [[Muscles - Anatomy & Physiology#Cardiac_Muscle|cardiac muscle]] and glands. Sympathetic innervation for this type of nerve fibre comes directly from the cranial cervical ganglion. However, parasympathetic innervation comes from several cranial nerves including the oculomotor nerve (cranial nerve III), the vestibulocochlear nerve (cranial nerve VIII), the glossopharyngeal nerve (cranial nerve IX) and the vagus nerve (cranial nerve X). Examples of where this type of fibre functions include the pupillary sphinter via the oculomotor nerve, glands of the nasal/oral cavity via the vestibulocochlear and glossopharyngeal nerves and thoracic/abdominal viscera via the vagus nerve.

:'''Gland Innervation Example'''

:''Brainstem —→ Parasympathetic nuculi —→ Parasympathetic ganglion —→ Gland etc.''

==Cranial Nerves==
There are three main groups of cranial nerves; special senses, innervation of the head muscles and innervation of structures originating from branchial arches. The special senses cranial nerves include the olfactory, ocular and vestibulocochlear. Cranial nerves related to the innervation of the head muscles include the oculomotor, trochlear, abducens and the hypoglossal nerves. Cranial nerves related to innervation of structures originating from branchial arches include the trigeminal, facial, glossopharyngeal, vagus and accessory nerves.

===Olfactory Nerve (I)===
Olfaction is part of the special senses cranial nerve group and represents the chemical senses of olfaction (smell) and gustation (taste). When chemical substances interact with our bodies they stimulate special sensory cells which in turn generate an action potential. The resultant impulse is sent to the brain via sensory afferent fibres and it is these fibres that represent the olfactory cranial nerve. Note: an action potential is only generated where a special sensory cell for that particular chemical substance exists. If no sensory cell exists, that chemical substance will go undetected. The olfactory neurosensory cells are found within the olfactory epithelium. The olfactory epithelium contains cilia on the surface of the cells to increase the surface area for chemical interactions.
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The olfactory nerve runs to the olfactory bulb which is found within the [[Forebrain - Anatomy & Physiology#Olfactory_Bulb|telencephalon]]. The olfactory nerve is a sensory nerve and is composed of many '''Special Visceral Afferent''' fibres. The fibres are formed into bundles that are referred to as 'Olfactory filaments'. The olfactory nerve passes through the [[Skull and Facial Muscles - Anatomy & Physiology#Ethmoid Bone (os ethmoidale)|'''Cribiform plate''']] and is surrounded by meningeal sheets including the [[Meninges - Anatomy & Physiology#Subarachnoid_Space|sub-arachnoid space]]. Therefore the route of the olfactory nerve represents a potential site for an infection to track towards the brain. Injury of this nerve can lead to 'anosmia', or loss of smell.
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The olfactory organ in dogs is extremely well developed and species such as canines use olfaction to orientate themselves in an environment in a way that humans do not. Olfactory cells are continuously replaced and are only viable sensory cells for between 30 - 60 days. This point is of importance as this is the only area in which nerve cells are able to be replaced or regenerated in adult animals and this area is now under research at Cambridge University for the treatment of damaged nerves and/or nerve disorders in nerves other than those involved in olfaction.

===Optic Nerve (II)===
The optic nerve is part of the special senses cranial nerves and represents the connection between the receptor cells of the [[Eye - Anatomy & Physiology#The Wall (retina, uvea and sclera)|retina]] and the [[Forebrain - Anatomy & Physiology|diencephalon]]. The optic nerve is a sensory nerve and is composed of '''Special Somatic Afferent fibres'''. Optic nerve axons pass from the optic disc of the retina to the brain, entering the skull via the [[Skull and Facial Muscles - Anatomy & Physiology#Sphenoid Bone (os_sphenoidale)|'''optic canal''']]. The majority of axons decussate at the [[Skull and Facial Muscles - Anatomy & Physiology#Sphenoid Bone (os_sphenoidale)|'''optic chiasm''']] before continuing as the optic tracts.
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The optic nerve can be examined clinically via a [[Neurological Eye Examination - Horse#Menace Response|menace response]] and anopsia (loss of vision) can be seen in injury.

===Oculomotor nerve (III)===
The oculomotor nerve is part of the group of cranial nerves responsible for innervating the [[Skull and Facial Muscles - Anatomy & Physiology#Facial_Muscles|muscles of the head]]. The nerves originate from the ventral [[Midbrain - Anatomy & Physiology|midbrain]] and is a motor nerve. It is composed of '''general somatic efferent fibres''' and '''general visceral efferent fibres'''. The general somatic efferent fibres of the oculomotor nerve are responsible for the motor function of four of the six [[Eye - Anatomy & Physiology#Around_the_Eye|external muscles of the eyeball]]; the 'dorsal rectus', 'medial rectus', 'ventral rectus', 'ventral oblique' and 'levator of the upper eyelid'. The general visceral efferent fibres of the oculomotor nerve control the 'sphincter pupillae' muscle (alters pupillary diameter) and the 'ciliaris' muscle (alters curvature of the lens).
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The oculomotor nerve has a pre-ganglionic nucleus in the midbrain and the nerve passes through the [[Skull_and_Facial_Muscles_-_Anatomy_%26_Physiology#Major_Foramen_and_Canals|'''orbital fissure''']], along with the trochlear, abducens and opthalmic branch (V1) of the trigeminal nerve. It synapses in the ciliary ganglion of the eye. During a clinical examination, horizontal eye movements (strabismus) or an absent [[Neurological_Eye_Examination_-_Horse#The_pupillary_light_reflex_(PLR)|pupillary light reflex (PLR)]] may indicate a problem.

===Trochlear nerve (IV)===
The trochlear nerve is part of the cranial nerve group responsible for innervation of the muscles of the head. The trochlear nerve originates from the dorsal mid-brain and is a motor nerve. It is composed of '''general somatic efferent fibres''' and is the smallest of the cranial nerves. The nerve is specifically responsible for the 'dorsal oblique muscle' muscle of the eye and also passes through the [[Skull and Facial Muscles - Anatomy & Physiology#Major Foramen and Canals|'''orbital fissure''']].
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During a clinical examination, a dorso-lateral strabismus may indicate a problem with this nerve.

===Trigeminal nerve (V)===
The trigeminal nerve is part of the cranial nerve group responsible for innervation of structures originating from branchial arches. The trigeminal nerve nuclei are in the area of the pons and medulla oblongata and it is the nerve of the 1st branchial arch. In general terms the trigeminal represents the sensory nerve of the head but also provides motor fibres to structures also associated with the 1st branchial arch. There are three primary branches of the trigeminal nerve; the '''Opthalmic nerve (V1)''', the ''' Maxillary nerve (V2)''' and the '''Mandibular nerve (V3)'''.

====Ophthalmic nerve (V1)====
The ophthalmic nerve is a sensory nerve composed of '''general somatic afferent fibres''' and passes through the [[Skull and Facial Muscles - Anatomy & Physiology#Major Foramen and Canals|'''orbital fissure''']]. As it enters the orbit of the eye it splits further into the '''lacrimal nerve''', the '''frontal nerve''', the '''nasociliary nerve''' and the '''infratrochlear nerve'''. Therefore the nerve supplies sensory fibres to many components of the orbit.

====Maxillary nerve (V2)====
The maxillary nerve is a sensory nerve composed of '''general somatic afferent fibres'''. The maxillary nerve passes through the [[Skull and Facial Muscles - Anatomy & Physiology#Major Foramen and Canals|'''round foramen''']] and the [[Skull and Facial Muscles - Anatomy & Physiology#Major Foramen and Canals|'''alar canal''']]. It also runs across the wall of the '''pterygopalatine fossa''' and enters the '''infraorbital canal''' via the '''maxillary foramen'''. Whilst in the infraorbital canal, the maxillary nerve branch then branches further into the '''infraorbital nerve''' which supplies sensory fibres to the teeth. On exiting the infraorbital canal via the infraorbital foramen, the maxillary nerve branches again into the '''zygomatic nerve''' which supplies sensory fibres to the horn and to the '''pterygopalatine nerve''' supplying sensory fibres to the palate.

====Mandibular nerve (V3)====
The mandibular nerve is a mixed sensory '''general somatic afferent fibres''' and motor '''general somatic efferent''' nerves. The mandibular nerve passes through the [[Skull_and_Facial_Muscles_-_Anatomy_%26_Physiology#Major_Foramen_and_Canals|'''oval foramen''']]. It provides motor branches to the [[Mastication|masticatory muscles]], the [[Larynx - Anatomy & Physiology#Intrinsic Musculature|ventral throat]] and [[Tongue - Anatomy & Physiology#Muscles|muscles of the palate]]. The mandibular nerve further branches into the '''masticatory nerve''', the '''masseteric nerve''' and the '''temporal nerve'''. The mandibular nerve provides sensory branches called the '''buccal nerve''', the '''auriculotemporal nerve''', and then itself divides into two smaller branches; the '''lingual nerve''' and the '''inferior alveolar nerve'''. The '''lingual nerve''' receives sensory fibres to the rostral 2/3 of the tongue and also connects some sensory taste fibres to parasympathetic salivary glands via the [[Tongue - Anatomy & Physiology#Innervation|'''chorda tympani''']]. The lingual branch of the glossopharyngeal nerve supplies sensory taste fibres to the caudal 1/3 of the tongue, while the facial nerve supplies sensory taste fibres to the rostral 2/3 of the tongue.

===Abducent nerve (VI)===
The abducent nerve is part of the cranial nerve group responsible for innervation of the muscles of the head. The abducent nerve originates from the medulla oblongata and is a motor nerve. It is composed of '''general somatic efferent fibres''' which are responsible for controlling the 'lateral rectus' muscle and the 'retractor bulbi' muscle of the eye. The nerve passes through the '''orbital fissure''' and can be found within the same layer of the meninges as the opthalmic branch (V1) of the trigeminal nerve (V).
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During a clinical examination, medial deviation strabismus may indicate a problem with this nerve.

===Facial nerve (VII)===
The facial nerve is part of the cranial nerve group responsible for the innervation of structures originating from the branchial arches. It originates from the medulla oblongata and from the second branchial arch. It has a common dura sheet with the opthalmic (V1) branch of the trigeminal nerve. The facial nerve is of a mixed composite and is made up of a number of different fibre types. It has a '''general somatic efferent fibre''' within the ear canal, a '''general visceral efferent fibre''' acting under parasympathetic control to some salivary glands, lacrimal glands, nasal cavity and palate, a '''special visceral afferent fibre''' providing taste to the rostral 2/3 of the tongue and finally it has a '''general somatic efferent fibre''' supplying motor function to the muscles of facial expression.
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The facial nerve enters the petrosal bone via the [[Skull and Facial Muscles - Anatomy & Physiology#Temporal Bone (os_temporale)|'''internal acoustic meatus''']] along with the vestibulocochlear nerve. The facial nerve also runs inside the '''facial canal'''. There are a number of intermediate branches which separate from the main facial nerve inside the facial canal including the '''greater petrosal nerve''', the '''stapedial nerve''' (motor) and the '''chorda tympani'''. These then emerges via the [[Skull and Facial Muscles - Anatomy & Physiology#Major Foramen and Canals|'''stylomastoid foramen''']] at the caudoventral aspect of the skull. The chorda tympani of the facial nerve represents the '''special visceral afferent fibre''' supplying taste to the rostral 2/3 of the tongue.
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There are also numerous external branches of the facial nerve once the facial nerve has left the facial canal. These include the '''internal auricular nerve''', the '''auriculopalpebral nerve''', the '''rostral auricular nerve''', the '''palpebral nerve''', the '''dorsal buccolabial nerve''', the '''ventral buccolabial nerve''', the '''ramus colli''', the '''digastric nerve''', the '''stylohoid nerve''' and the '''caudal auricular nerve'''.
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The facial nerve supplies motor innervation to the muscles of facial expression. These are superficial flat, thin muscles that originate from bony areas of fascia and then radiate out around the skin. They may also often from sphincters such as around the mouth and eye.
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During a clinical examination any facial paralysis, drooling or abscence of blinking may indicate a problem with the facial nerve.

===Vestibulocochlear nerve (VIII)===
The vestibulocochlear nerve is part of the special senses group of cranial nerves and is made up of two components; the vestibular nerve and the cochlear nerve. The vestibular nerve is responsible for balance whilst the cochlear nerve is responsible for hearing. The nerves send impulses from the inner ear which contains the [[Ear - Anatomy & Physiology#Vestibular Receptors and Balance|vestibular apparatus]] and [[Ear - Anatomy & Physiology#The Cochlea|cochlea]]. The vestibulocochlear nerve is a sensory nerve made up of '''special somatic afferent fibres'''. It passes through the '''internal acoustic meatus''' and into the '''petrosal bone'''. The facial nerve also takes this route.
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Clinical problems with the vestibulocochlear nerve would be indicated on examination by changes in hearing and/or horizontal and vertical eye movements (strabismus and [[Vestibular System Examination|nystagmus]]). A head tilt is also associated with this nerve.

===Glossopharyngeal nerve (IX)===
The glossopharyngeal nerve is part of the group of cranial nerves responsible for innervation of structures derived from the branchial arches. This nerve innervates structures related to the third branchial arch. It is also part of a group together with the vagus and accessory nerves that passes through the '''jugular foramen''' which is termed the '''vagus group'''. The glossopharyngeal nerve has cell bodies that are referred to as '''nucleus ambiguus'''. The glossopharyngeal nerve originates from the medulla oblongata and has several branches including the '''pharyngeal nerve''', the '''lingual nerve''' and the '''tympanic branches'''.
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The glossopharyngeal nerve is composed of many fibre types including '''general somatic efferent fibres''' that innervate the stylopharyngeus muscle; the '''general visceral afferent fibres''' that provide sensory information from the carotid body, the pharynx and the middle ear; the '''general visceral efferent fibres''' that provide parasympathetic innervation to the parotid and zygomatic salivary glands; the '''special visceral afferent fibres''' that provide taste caudal to the tongue and finally the '''general somatic afferent fibres''' that provide sensory information from the external ear.
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The '''lingual branch''' of the glossopharyngeal nerve provides '''general somatic afferent fibres''' and '''special visceral afferent fibres''' to the caudal 1/3 of the tongue.
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On clinical examination, choking or dysphagia as a result of malfunctioning or absent pharyngeal reflexes would indicate a problem with the glossopharyngeal nerve.

===Vagus nerve (X)===
The vagus nerve is part of the group of cranial nerves responsible for innervation of structures derived from the branchial arches. It is also part of a group together with the glossopharyngeal and accessory nerves that passes through the '''jugular foramen''' which is termed the '''vagus group'''. The vagus nerve innervates structures related to the fourth branchial arch. The vagus nerve has cell bodies that are referred to as '''nucleus ambiguus'''.
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The vagus nerve is composed of many different types of nerve fibre including '''general somatic efferent fibres''' supplying motor function to the muscles of the larynx, pharynx, palate and oesophagus; '''general visceral afferent fibres''' to the base of the tongue, pharynx and larynx; '''general visceral efferent fibres''' for parasympathetic supply of the thoracic and abdominal viscera; '''special visceral afferent fibres''' supplying taste to regions of the epiglottis and palate and finally '''general somatic afferent fibres''' to the external ear and the dura mater. The vagus nerve also supplies '''general somatic afferent fibres''' and '''special visceral afferent fibres''' to the root of the tongue.
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There are many functional components of the vagus nerve including the heart, larynx, pharynx and many other viscera. On clinical examination any changes related to gag reflexes, blood pressure or heart rate, changes in 'voice' or inspiratory dyspnoea may indicate a problem with the vagus nerve.

===Accessory nerve (XI)===
The accessory nerve is part of the group of cranial nerves responsible for innervation of structures derived from the branchial arches. It is also part of a group together with the glossopharyngeal and vagus nerves that passes through the '''jugular foramen''' which is termed the '''vagus group'''. The accessory nerve supplies structures related to the fourth branchial arch. The accessory nerve has cell bodies that are referred to as '''nucleus ambiguus''' and originate in the medulla oblongata. The cranial root of the accessory nerve actually contributes to the vagus nerve and to the striated muscles of the pharynx, larynx, palate and oesophagus.

However, the accessory nerve also contributes to the cervical spinal cord and spinal root through the '''foramen magnum''' providing innervation to muscles of the neck. The spinal root of the accessory nerve branches into the '''dorsal branch''' and the '''ventral branch'''. The dorsal branch innervates the brachiocephalicus, trapezius and omotransversarius muscles of the dorsal neck. The ventral branch innervates the sternocephalicus muscle.
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During clinical examination any difficulties in turning the neck or muscle atrophy around the dorsal and ventral neck may indicate a problem with the accessory nerve.

===Hypoglossal nerve (XII)===
The hypoglossal nerve is part of the group of cranial nerves responsible for the control of muscles of the head. It is in part a cervical nerve due to its caudal position on the [[Hindbrain - Anatomy & Physiology|brain stem]]. The nerve is composed of '''general somatic efferent fibres''' which control the intrinsic and extrinsic muscles of the tongue (together with other nerves including the lingual nerve, facial nerve, lingual branch of the glossopharyngeal nerve and the vagus nerve). The nucleus of the nerve is located within the medulla oblongata of the brain stem and it passes through the '''hypoglossal canal'''.
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During a clinical examination any deviation of the tongue may indicate a problem with this nerve. Deviation of the tongue is always to the side of the lesion.

==Cranial Nerve Summary/Revision Tables==
These tables are designed to be a revision aid and do not contain any specific details. Details regarding each nerve are in the written section above.
===Cranial Nerve Location and Routes===
A table summarising the cranial nerve location and route information in the section above has been included to summarise the key points for each cranial nerve. For the fibre type please see the Fibre Type section (heading 2 above) using the fibre type link in the table.

{| style="width:100%; height:200px" border="1"

! '''Nerve'''
! '''Attatchment to brain'''
! '''Exit Foramen'''
! '''[[#Cranial Nerve Fibre Types|Fibre Type]]'''
! '''Location of cell bodies'''
! '''Distribution'''

|-
| '''I - Olfactory'''
| Olfactory bulb
| Cribriform plate
| SVA
| Olfactory epithelium
| Olfactory epithelium
|-

| '''II - Optic'''
| Diencephalon (via optic chiasm)
| Optic canal
| SSA
| Retina
| Retina

|-
| '''III - Oculomotor'''
| Midbrain
| Orbital fissure
| GSE + GVE
| Oculomotor motor nucleus
Parasympathetic nucleus of oculomotor nerve
| Extraoccular mm.
Constrictor pupilli

|-
| '''IV - Trochlear'''
| Midbrain (dorsal)
| Orbital fissure
| GSE
| Trochlear nucleus
| Dorsal oblique mm.
|-

| '''V - Trigeminal'''
| Pons
| V1 - Orbital fissure
V2 - Round Foramen/Rostral alar foramen

V3 - Oval Foramen
| V1 - GSA
V2 - GSA

V3 - GSA & GSE
| V1 - Trigeminal gangion (GSA)
V2 - Trigeminal ganglion (GSA)

V3 - Trigeminal ganglion (GSA), Geniculate ganglion (SVA), Trigeminal motor nucleus (motor)
| V1 - Eye region
V2 - Upper jaw inc. teeth

V3 - mm. of arch 1, lower jaw, rostral 2/3 tongue

|-
| '''VI - Abducens'''
| Medulla oblongata
| Orbital fissure
| GSE
| Abducent nucleus
| Lateral rectus and retractor bulbi mm.
|-

|-
| '''VII - Facial'''
| Medulla oblongata
| Internal acoustic meatus/facial canal/stylomastoid foramen
| SVA + GVE + GSE + GSA
| Facial motor nucleus
Geniculate ganglion
| mm. of arch 2
Submaxillary and sublingual glands

Rostral 2/3 tongue
|-

|-
| '''VIII - Vestibulocochlear'''
| Medulla oblongata
| Internal acoustic meatus
| SSA
| Vestibular ganglion, spiral ganglion
| Maculae and cristae
|-

|-
| '''IX - Glossopharyngeal'''
| Medulla oblongata
| Jugular foramen/tympanooccipital fissure
| GSE GVA GVE GSA SVA
| Glossopharyngeal ganglion
Glossopharyngeal parasympathetic nucleus, nucleus ambiguus - mm. arch 3
| Carotid gland
Caudal 1/3 tongue
mm. of arch 3

Carotid body
|-

|-
| '''X - Vagus'''
| Medulla oblongata
| Jugular foramen/tympanooccipital fissure
| GSE GVA GVE SVA GSA
| Vagal ganglion - (amongst others)
Vagal parasympathetic nucleus, nucleus ambiguus
| Thoracic and abdominal organs
mm. of arches 4-6
Pharynx and larynx
External ear
|-

|-
| '''XI - Accessory'''
| Medulla oblongata
| Jugular foramen/tympanooccipital fissure
| GSE
| Nucleus ambiguus, accessory motor nucleus (cervical spinal cord)
| Trapezius m. etc
|-

|-
| '''XII - Hypoglossal'''
| Medulla oblongata
| Hypoglossal canal
| GSE
| Hypoglossal nucleus
| Tongue mm.
|-
|}

===Cranial Nerves Functions===
This table is designed to provide the basic function of each cranial nerve and has also been designed as a summary/revision aid.
{| border="1" cellpadding="7"
|-style="background:#B0E0E6; color:black"
!'''#'''
!'''Name'''
!'''Nuclei'''
!'''Function'''
|-
|'''I'''
| '''''Olfactory nerve'''''
|Anterior olfactory nucleus
| Transmits the sense of smell
|- style="background:#F0F8FF; color:black"
| '''II'''
| '''''Optic nerve'''''
| Lateral geniculate nucleus
| Transmits visual information to the brain
|-
| '''III''' || '''''Oculomotor nerve''''' || Oculomotor nucleus, Edinger-Westphal nucleus || Innervates the dorsal rectus, medial rectus, ventral rectus, and ventral oblique, which collectively perform most eye movements
|- style="background:#F0F8FF; color:black"
| '''IV'''
| '''''Trochlear nerve'''''
| Trochlear nucleus
| Innervates the superior oblique muscle, which depresses, pulls laterally, and intorts the eyeball
|-
| '''V''' || '''''Trigeminal nerve''''' || Principal sensory trigeminal nucleus, Spinal trigeminal nucleus, Mesencephalic trigeminal nucleus, Trigeminal motor nucleus || Receives sensation from the face and innervates the muscles of mastication
|- style="background:#F0F8FF; color:black"
| '''VI'''
| '''''Abducens nerve'''''
| Abducens nucleus
| Innervates the lateral rectus, which abducts the eye and the retractor bulbi which forces the third eyelid across the surface of the cornea as a protective mechanism.
|-
| '''VII''' || '''''Facial nerve''''' || Facial nucleus, Solitary nucleus, Superior salivary nucleus || Provides motor innervation to the muscles of facial expression and stapedius, receives the special sense of taste from the anterior 2/3 of the tongue, and provides secretomotor innervation to the salivary glands (except parotid) and the lacrimal gland
|- style="background:#F0F8FF; color:black"
|'''VIII'''
| '''''Vestibulocochlear nerve'''''
| Vestibular nuclei, Cochlear nuclei
| Senses sound, rotation and gravity (essential for balance & movement)
|-
| '''IX''' || '''''Glossopharyngeal nerve''''' || Nucleus ambiguus, Inferior salivary nucleus, Solitary nucleus || Receives taste from the posterior 1/3 of the tongue, provides secretomotor innervation to the parotid gland, and provides motor innervation to the stylopharyngeus
|- style="background:#F0F8FF; color:black"
| '''X'''
| '''''Vagus nerve'''''
| Nucleus ambiguus, Dorsal motor vagal nucleus, Solitary nucleus
| Supplies branchiomotor innervation to most laryngeal and pharyngeal muscles; provides parasympathetic fibers to nearly all thoracic and abdominal viscera down to the splenic flexure; and receives the special sense of taste from the epiglottis
|-
| '''XI''' || '''''Accessory nerve''''' || Nucleus ambiguus, Spinal accessory nucleus || Controls muscles of the neck and overlaps with functions of the vagus
|- style="background:#F0F8FF; color:black"
| '''XII'''
| '''''Hypoglossal nerve'''''
| Hypoglossal nucleus
| Provides motor innervation to the intrinsic muscles of the tongue and other glossal muscles
|}

==Learning Mnemonic==
There are various ways to memorise the cranial nerves including both the names of the actual nerves themselves and also their functions/type of nerve fibre. Here are some examples for the nerve names and also some for the type of nerve.
===Nerve Name Mnemonics===
====Mnemonic 1====
* '''O'''h (''O''lfactory I)
* '''O'''h (''O''ptic II)
* '''O'''h (''O''culomotor III)
* '''T'''o (''T''rochlear IV)
* '''T'''ouch (''T''rigeminal V)
* '''A'''nd (''A''bducens VI)
* '''F'''eel (''F''acial VII)
* '''A''' (''A''uditory/Vestibulocochlear VIII)
* '''G'''irl's (''G''lossopharyngeal IX)
* '''V'''ery (''V''agus X)
* '''S'''oft (''S''pinal/Accessory XI)
* '''H'''ands (''H''ypoglossal XII)
====Mnemonic 2====
* '''O'''h (''O''lfactory I)
* '''O'''nce (''O''ptic II)
* '''O'''ne (''O''culomotor III)
* '''T'''akes (''T''rochlear IV)
* '''T'''he (''T''rigeminal V)
* '''A'''natomy (''A''bducens VI)
* '''F'''inal (''F''acial VII)
* '''A''' (''A''uditory/Vestibulocochlear VIII)
* '''G'''ood (''G''lossopharyngeal IX)
* '''V'''acation (''V''agus X)
* '''S'''eems (''S''pinal/Accessory XI)
* '''H'''eavenly (''H''ypoglossal XII)
====Mnemonic 3====
* '''O'''nly (''O''lfactory I)
* '''O'''ffer (''O''ptic II)
* '''O'''nce (''O''culomotor III)
* '''T'''o (''T''rochlear IV)
* '''T'''ry (''T''rigeminal V)
* '''A'''nd (''A''bducens VI)
* '''F'''ind (''F''acial VII)
* '''V'''erdant (''A''uditory/Vestibulocochlear VIII)
* '''G'''reen (''G''lossopharyngeal IX)
* '''V'''erges (''V''agus X)
* '''A'''nd (''S''pinal/Accessory XI)
* '''H'''edges (''H''ypoglossal XII)

===Nerve Type Mnemonics===
For the mnemonic below ''S = sensory'', ''M = motor'' and ''B = both'' (sensory and motor).
* '''S'''ome
* '''S'''ay
* '''M'''arry
* '''M'''oney
* '''B'''ut
* '''M'''y
* '''B'''rother
* '''S'''ays
* '''B'''ig
* '''B'''usiness
* '''M'''akes
* '''M'''oney

{{Learning
|videos = [[Video: Lateral surface of the head of the dog potcast 2|Lateral surface of the head of the dog potcast 2]]<br>[[Video: Canine orbit and sagittal section of the canine head|Canine orbit and sagittal section of the canine head]]<br>[[Video: Lateral surface of the head of the dog potcast 3|Lateral surface of the head of the dog potcast]]<br>[[Video: Lateral surface of the head of the dog potcast 5|Lateral surface of the head of the dog potcast 5]]<br>
}}

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[[Category:Nervous System - Anatomy & Physiology]]
[[Category:A&P Done]]

Cranial Nerves - Anatomy & Physiology

2022-10-27T19:30:07Z

Roytwv:

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[[File:Brain human normal inferior view with labels en.svg|thumb|right|400px|Ventral brain showing labelled cranial nerves, WikiCommons]]
==Introduction==
Cranial nerves are those nerves which arise from the brain and [[Hindbrain - Anatomy & Physiology|brain stem]] rather than the spinal cord. Nerves arising from the spinal cord are the [[PNS Structure - Anatomy & Physiology|spinal nerves]]. There are 12 pairs of cranial nerves and these pairs of nerves passage through [[Skull and Facial Muscles - Anatomy & Physiology|foramina in the skull]], either individually or in groups. Cranial nerves are traditionally referred to by Roman numerals and these numerals begin cranially and run caudally.
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The most cranial nerve is the '''Olfactory nerve (I)''' which runs from the nasal cavity through to the olfactory bulb. The next most cranial is the '''Optic nerve (II)''' which runs from the eyes to the [[Forebrain - Anatomy & Physiology#Thalamus|thalamus]]. Cranial nerves III to XII all exit from the brain stem and innervate the head, neck and organs in the thorax and abdomen. In order of most cranial to caudal, these include the '''Oculomotor nerve (III)''', the '''Trochlear nerve (IV)''', the '''Trigeminal nerve (V)''', the '''Abducens nerve (VI)''', the '''Facial nerve (VII)''', the '''Vestibulocochlear nerve (VIII)''', the '''Glossopharyngeal nerve (IX)''', the '''Vagus nerve (X)''', the '''Accessory nerve (XI)''' and the '''Hypoglossal nerve (XII)'''.
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Many of the cranial nerves with nuclei within the brain stem contain sensory and motor neurone components. The sensory fibre components have their cell bodies located in ganglia outside the central nervous system and the motor fibre element have their cell bodies within the central nervous system.

==Cranial Nerve Fibre Types==
Prior to a full explanation of each cranial nerve function, physiology, anatomy and particularly composition, the numerous types of nerve fibre found in cranial nerves must be explained to ensure that the following can be better understood.

Nerve fibres can undertake numerous roles within the body and their function is dictated by what type of fibre the nerve is composed of. A classification scheme is used to describe the type of fibres found within the cranial nerves and therefore provides a better understanding of the function and composition of that particular nerve. Below is a brief outline of this nerve fibre classification.

===Afferent Fibres - Sensory===
====General Somatic Afferent (GSA)====
This type of fibre is used in the majority of basic senses including temperature, touch and [[Pain|pain]]. These fibres mainly supply sensation to various areas of the head including to the skin and face via the trigeminal nerve (cranial nerve V); to the skin of the [[Ear - Anatomy & Physiology#Outer_Ear|external ear]] via the trigeminal nerve (cranial nerve V), the facial nerve (cranial nerve VII), the glossopharyngeal nerve (cranial nerve IX) and via the vagus nerve (cranial nerve X); to the mucosae of the [[Oral Cavity Overview - Anatomy & Physiology|oral cavity]] via the trigeminal nerve (cranial nerve V) and to the [[Meninges - Anatomy & Physiology|meningies]] of the brain via the trigeminal nerve (cranial nerve V) and the vagus nerve (cranial nerve X).

:'''Skin Sensation Example'''

:''Sensory cortex —→ Thalamus —→ Trigeminal nuclei —→ Trigeminal ganglion —→ Skin etc.''

====Special Somatic Afferent (SSA)====
The special signifies that this fibre type is found in nerves related to the special senses which include [[Eye - Anatomy & Physiology#Vision|vision]] and [[Ear - Anatomy & Physiology#Function_-_Hearing|hearing]]. This therefore relates to the optic nerves (cranial nerve II) and the auditory/vestibular systems which are the vestibulocochlear nerves (cranial nerve VIII).

:'''Vision Example'''

:''Occipital cortex —→ Thalamus MGN —→ Rostral colliculus/Retinal ganglion cell —→ Bipolar cell —→ [[Eye - Anatomy & Physiology|Vision]]''

:'''Hearing Example'''

:''Temporal cortex —→ Thalamus MGN —→ Caudal colliculus and hindbrain —→ Spiral ganglion —→ [[Ear - Anatomy & Physiology|Hearing]]''

====General Visceral Afferent (GVA)====
This fibre type is commonly found in sensory nerves to organs and to sensory tissues related to chemicals. These include fibres found in the glossopharyngeal nerves (cranial nerve IX) and the vagus nerves (cranial nerve X).

:'''Organ Sensory Example'''

:''Sensory cortex —→ Thalamus —→ Cranial nerve nuculi —→ Nerve ganglion —→ Organs etc.''

====Special Visceral Afferent (SVA)====
This fibre type is found again in special sense organs related to the sensing of chemicals and therefore including [[Gustatory System - Anatomy & Physiology|taste]] and [[olfaction]]. The olfactory sense relates to the olfactory nerve (cranial nerve I) and the taste senses relate to the facial nerve (cranial nerve VII), the glossopharyngeal nerve (cranial nerve IX) and the vagus nerve (cranial nerve X). The sense of taste is performed by the gustatory organ which are cells located in gustatory papillae in the mucous membrane of the dorsal side of the tongue. Taste buds can also be found in the soft palate, pharynx, larynx, lips and cheeks.

:'''Olfaction Example'''

:''Piriform cortex —→ Olfactory tubercle —→ Olfactory Bulb —→ [[Nose - Anatomy & Physiology|Smell]]''

:'''Taste Example'''

:''Sensory cortex —→ Thalamus —→ Hindbrain (VII, IX, X) —→ Ganglion —→ [[Gustatory System - Anatomy & Physiology|Taste]]''

===Efferent Fibres - Motor===
====General Somatic Efferent (GSE)====
This type of nerve fibre is mainly found in nerves supplying [[Muscles - Anatomy & Physiology#Skeletal_Muscle|skeletal muscles]]. Motor fibres such as these undertake numerous roles within the body such as control over the external ocular muscles via the oculomotor nerve (cranial nerve III), the trochlear nerve (cranial nerve IV) and the abducent nerve (cranial nerve VI); or for example the muscles around the dorsal and ventral neck including the brachiocephalicus, trapezius, omotransversarius and the sternocephalicus which are all supplied by the accessory nerve (cranial nerve XI).

:'''Motor Nerve Innervation Example'''

:''Motor cortex —→ Motor nuculi —→ Muscle''

====General Visceral Efferent (GVE)====
This type of nerve fibre is found in nerves supplying [[Muscles - Anatomy & Physiology#Smooth_Muscle|smooth muscle]], [[Muscles - Anatomy & Physiology#Cardiac_Muscle|cardiac muscle]] and glands. Sympathetic innervation for this type of nerve fibre comes directly from the cranial cervical ganglion. However, parasympathetic innervation comes from several cranial nerves including the oculomotor nerve (cranial nerve III), the vestibulocochlear nerve (cranial nerve VIII), the glossopharyngeal nerve (cranial nerve IX) and the vagus nerve (cranial nerve X). Examples of where this type of fibre functions include the pupillary sphinter via the oculomotor nerve, glands of the nasal/oral cavity via the vestibulocochlear and glossopharyngeal nerves and thoracic/abdominal viscera via the vagus nerve.

:'''Gland Innervation Example'''

:''Brainstem —→ Parasympathetic nuculi —→ Parasympathetic ganglion —→ Gland etc.''

==Cranial Nerves==
There are three main groups of cranial nerves; special senses, innervation of the head muscles and innervation of structures originating from branchial arches. The special senses cranial nerves include the olfactory, ocular and vestibulocochlear. Cranial nerves related to the innervation of the head muscles include the oculomotor, trochlear, abducens and the hypoglossal nerves. Cranial nerves related to innervation of structures originating from branchial arches include the trigeminal, facial, glossopharyngeal, vagus and accessory nerves.

===Olfactory Nerve (I)===
Olfaction is part of the special senses cranial nerve group and represents the chemical senses of olfaction (smell) and gustation (taste). When chemical substances interact with our bodies they stimulate special sensory cells which in turn generate an action potential. The resultant impulse is sent to the brain via sensory afferent fibres and it is these fibres that represent the olfactory cranial nerve. Note: an action potential is only generated where a special sensory cell for that particular chemical substance exists. If no sensory cell exists, that chemical substance will go undetected. The olfactory neurosensory cells are found within the olfactory epithelium. The olfactory epithelium contains cilia on the surface of the cells to increase the surface area for chemical interactions.
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The olfactory nerve runs to the olfactory bulb which is found within the [[Forebrain - Anatomy & Physiology#Olfactory_Bulb|telencephalon]]. The olfactory nerve is a sensory nerve and is composed of many '''Special Visceral Afferent''' fibres. The fibres are formed into bundles that are referred to as 'Olfactory filaments'. The olfactory nerve passes through the [[Skull and Facial Muscles - Anatomy & Physiology#Ethmoid Bone (os ethmoidale)|'''Cribiform plate''']] and is surrounded by meningeal sheets including the [[Meninges - Anatomy & Physiology#Subarachnoid_Space|sub-arachnoid space]]. Therefore the route of the olfactory nerve represents a potential site for an infection to track towards the brain. Injury of this nerve can lead to 'anosmia', or loss of smell.
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The olfactory organ in dogs is extremely well developed and species such as canines use olfaction to orientate themselves in an environment in a way that humans do not. Olfactory cells are continuously replaced and are only viable sensory cells for between 30 - 60 days. This point is of importance as this is the only area in which nerve cells are able to be replaced or regenerated in adult animals and this area is now under research at Cambridge University for the treatment of damaged nerves and/or nerve disorders in nerves other than those involved in olfaction.

===Optic Nerve (II)===
The optic nerve is part of the special senses cranial nerves and represents the connection between the receptor cells of the [[Eye - Anatomy & Physiology#The Wall (retina, uvea and sclera)|retina]] and the [[Forebrain - Anatomy & Physiology|diencephalon]]. The optic nerve is a sensory nerve and is composed of '''Special Somatic Afferent fibres'''. Optic nerve axons pass from the optic disc of the retina to the brain, entering the skull via the [[Skull and Facial Muscles - Anatomy & Physiology#Sphenoid Bone (os_sphenoidale)|'''optic canal''']]. The majority of axons decussate at the [[Skull and Facial Muscles - Anatomy & Physiology#Sphenoid Bone (os_sphenoidale)|'''optic chiasm''']] before continuing as the optic tracts.
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The optic nerve can be examined clinically via a [[Neurological Eye Examination - Horse#Menace Response|menace response]] and anopsia (loss of vision) can be seen in injury.

===Oculomotor nerve (III)===
The oculomotor nerve is part of the group of cranial nerves responsible for innervating the [[Skull and Facial Muscles - Anatomy & Physiology#Facial_Muscles|muscles of the head]]. The nerves originate from the ventral [[Midbrain - Anatomy & Physiology|midbrain]] and is a motor nerve. It is composed of '''general somatic efferent fibres''' and '''general visceral efferent fibres'''. The general somatic efferent fibres of the oculomotor nerve are responsible for the motor function of four of the six [[Eye - Anatomy & Physiology#Around_the_Eye|external muscles of the eyeball]]; the 'dorsal rectus', 'medial rectus', 'ventral rectus', 'ventral oblique' and 'levator of the upper eyelid'. The general visceral efferent fibres of the oculomotor nerve control the 'sphincter pupillae' muscle (alters pupillary diameter) and the 'ciliaris' muscle (alters curvature of the lens).
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The oculomotor nerve has a pre-ganglionic nucleus in the midbrain and the nerve passes through the [[Skull_and_Facial_Muscles_-_Anatomy_%26_Physiology#Major_Foramen_and_Canals|'''orbital fissure''']], along with the trochlear, abducens and opthalmic branch (V1) of the trigeminal nerve. It synapses in the ciliary ganglion of the eye. During a clinical examination, horizontal eye movements (strabismus) or an absent [[Neurological_Eye_Examination_-_Horse#The_pupillary_light_reflex_(PLR)|pupillary light reflex (PLR)]] may indicate a problem.

===Trochlear nerve (IV)===
The trochlear nerve is part of the cranial nerve group responsible for innervation of the muscles of the head. The trochlear nerve originates from the dorsal mid-brain and is a motor nerve. It is composed of '''general somatic efferent fibres''' and is the smallest of the cranial nerves. The nerve is specifically responsible for the 'dorsal oblique muscle' muscle of the eye and also passes through the [[Skull and Facial Muscles - Anatomy & Physiology#Major Foramen and Canals|'''orbital fissure''']].
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During a clinical examination, a dorso-lateral strabismus may indicate a problem with this nerve.

===Trigeminal nerve (V)===
The trigeminal nerve is part of the cranial nerve group responsible for innervation of structures originating from branchial arches. The trigeminal nerve nuclei are in the area of the pons and medulla oblongata and it is the nerve of the 1st branchial arch. In general terms the trigeminal represents the sensory nerve of the head but also provides motor fibres to structures also associated with the 1st branchial arch. There are three primary branches of the trigeminal nerve; the '''Opthalmic nerve (V1)''', the ''' Maxillary nerve (V2)''' and the '''Mandibular nerve (V3)'''.

====Ophthalmic nerve (V1)====
The ophthalmic nerve is a sensory nerve composed of '''general somatic afferent fibres''' and passes through the [[Skull and Facial Muscles - Anatomy & Physiology#Major Foramen and Canals|'''orbital fissure''']]. As it enters the orbit of the eye it splits further into the '''lacrimal nerve''', the '''frontal nerve''', the '''nasociliary nerve''' and the '''infratrochlear nerve'''. Therefore the nerve supplies sensory fibres to many components of the orbit.

====Maxillary nerve (V2)====
The maxillary nerve is a sensory nerve composed of '''general somatic afferent fibres'''. The maxillary nerve passes through the [[Skull and Facial Muscles - Anatomy & Physiology#Major Foramen and Canals|'''round foramen''']] and the [[Skull and Facial Muscles - Anatomy & Physiology#Major Foramen and Canals|'''alar canal''']]. It also runs across the wall of the '''pterygopalatine fossa''' and enters the '''infraorbital canal''' via the '''maxillary foramen'''. Whilst in the infraorbital canal, the maxillary nerve branch then branches further into the '''infraorbital nerve''' which supplies sensory fibres to the teeth. On exiting the infraorbital canal via the infraorbital foramen, the maxillary nerve branches again into the '''zygomatic nerve''' which supplies sensory fibres to the horn and to the '''pterygopalatine nerve''' supplying sensory fibres to the palate.

====Mandibular nerve (V3)====
The mandibular nerve is a mixed sensory '''general somatic afferent fibres''' and motor '''general somatic efferent''' nerves. The mandibular nerve passes through the [[Skull_and_Facial_Muscles_-_Anatomy_%26_Physiology#Major_Foramen_and_Canals|'''oval foramen''']]. It provides motor branches to the [[Mastication|masticatory muscles]], the [[Larynx - Anatomy & Physiology#Intrinsic Musculature|ventral throat]] and [[Tongue - Anatomy & Physiology#Muscles|muscles of the palate]]. The mandibular nerve further branches into the '''masticatory nerve''', the '''masseteric nerve''' and the '''temporal nerve'''. The mandibular nerve provides sensory branches called the '''buccal nerve''', the '''auriculotemporal nerve''', and then itself divides into two smaller branches; the '''lingual nerve''' and the '''inferior alveolar nerve'''. The '''lingual nerve''' receives sensory fibres to the rostral 2/3 of the tongue and also connects some sensory taste fibres to parasympathetic salivary glands via the [[Tongue - Anatomy & Physiology#Innervation|'''chorda tympani''']]. The lingual branch of the glossopharyngeal nerve supplies sensory taste fibres to the caudal 1/3 of the tongue, while the facial nerve supplies sensory taste fibres to the rostral 2/3 of the tongue.

===Abducent nerve (VI)===
The abducent nerve is part of the cranial nerve group responsible for innervation of the muscles of the head. The abducent nerve originates from the medulla oblongata and is a motor nerve. It is composed of '''general somatic efferent fibres''' which are responsible for controlling the 'lateral rectus' muscle and the 'retractor bulbi' muscle of the eye. The nerve passes through the '''orbital fissure''' and can be found within the same layer of the meninges as the opthalmic branch (V1) of the trigeminal nerve (V).
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During a clinical examination, medial deviation strabismus may indicate a problem with this nerve.

===Facial nerve (VII)===
The facial nerve is part of the cranial nerve group responsible for the innervation of structures originating from the branchial arches. It originates from the medulla oblongata and from the second branchial arch. It has a common dura sheet with the opthalmic (V1) branch of the trigeminal nerve. The facial nerve is of a mixed composite and is made up of a number of different fibre types. It has a '''general somatic efferent fibre''' within the ear canal, a '''general visceral efferent fibre''' acting under parasympathetic control to some salivary glands, lacrimal glands, nasal cavity and palate, a '''special visceral afferent fibre''' providing taste to the rostral 2/3 of the tongue and finally it has a '''general somatic efferent fibre''' supplying motor function to the muscles of facial expression.
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The facial nerve enters the petrosal bone via the [[Skull and Facial Muscles - Anatomy & Physiology#Temporal Bone (os_temporale)|'''internal acoustic meatus''']] along with the vestibulocochlear nerve. The facial nerve also runs inside the '''facial canal'''. There are a number of intermediate branches which separate from the main facial nerve inside the facial canal including the '''greater petrosal nerve''', the '''stapedial nerve''' (motor) and the '''chorda tympani'''. These then emerges via the [[Skull and Facial Muscles - Anatomy & Physiology#Major Foramen and Canals|'''stylomastoid foramen''']] at the caudoventral aspect of the skull. The chorda tympani of the facial nerve represents the '''special visceral afferent fibre''' supplying taste to the rostral 2/3 of the tongue.
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There are also numerous external branches of the facial nerve once the facial nerve has left the facial canal. These include the '''internal auricular nerve''', the '''auriculopalpebral nerve''', the '''rostral auricular nerve''', the '''palpebral nerve''', the '''dorsal buccolabial nerve''', the '''ventral buccolabial nerve''', the '''ramus colli''', the '''digastric nerve''', the '''stylohoid nerve''' and the '''caudal auricular nerve'''.
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The facial nerve supplies motor innervation to the muscles of facial expression. These are superficial flat, thin muscles that originate from bony areas of fascia and then radiate out around the skin. They may also often from sphincters such as around the mouth and eye.
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During a clinical examination any facial paralysis, drooling or abscence of blinking may indicate a problem with the facial nerve.

===Vestibulocochlear nerve (VIII)===
The vestibulocochlear nerve is part of the special senses group of cranial nerves and is made up of two components; the vestibular nerve and the cochlear nerve. The vestibular nerve is responsible for balance whilst the cochlear nerve is responsible for hearing. The nerves send impulses from the inner ear which contains the [[Ear - Anatomy & Physiology#Vestibular Receptors and Balance|vestibular apparatus]] and [[Ear - Anatomy & Physiology#The Cochlea|cochlea]]. The vestibulocochlear nerve is a sensory nerve made up of '''special somatic afferent fibres'''. It passes through the '''internal acoustic meatus''' and into the '''petrosal bone'''. The facial nerve also takes this route.
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Clinical problems with the vestibulocochlear nerve would be indicated on examination by changes in hearing and/or horizontal and vertical eye movements (strabismus and [[Vestibular System Examination|nystagmus]]). A head tilt is also associated with this nerve.

===Glossopharyngeal nerve (IX)===
The glossopharyngeal nerve is part of the group of cranial nerves responsible for innervation of structures derived from the branchial arches. This nerve innervates structures related to the third branchial arch. It is also part of a group together with the vagus and accessory nerves that passes through the '''jugular foramen''' which is termed the '''vagus group'''. The glossopharyngeal nerve has cell bodies that are referred to as '''nucleus ambiguus'''. The glossopharyngeal nerve originates from the medulla oblongata and has several branches including the '''pharyngeal nerve''', the '''lingual nerve''' and the '''tympanic branches'''.
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The glossopharyngeal nerve is composed of many fibre types including '''general somatic efferent fibres''' that innervate the stylopharyngeus muscle; the '''general visceral afferent fibres''' that provide sensory information from the carotid body, the pharynx and the middle ear; the '''general visceral efferent fibres''' that provide parasympathetic innervation to the parotid and zygomatic salivary glands; the '''special visceral afferent fibres''' that provide taste caudal to the tongue and finally the '''general somatic afferent fibres''' that provide sensory information from the external ear.
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The '''lingual branch''' of the glossopharyngeal nerve provides '''general somatic afferent fibres''' and '''special visceral afferent fibres''' to the caudal 1/3 of the tongue.
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On clinical examination, choking or dysphagia as a result of malfunctioning or absent pharyngeal reflexes would indicate a problem with the glossopharyngeal nerve.

===Vagus nerve (X)===
The vagus nerve is part of the group of cranial nerves responsible for innervation of structures derived from the branchial arches. It is also part of a group together with the glossopharyngeal and accessory nerves that passes through the '''jugular foramen''' which is termed the '''vagus group'''. The vagus nerve innervates structures related to the fourth branchial arch. The vagus nerve has cell bodies that are referred to as '''nucleus ambiguus'''.
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The vagus nerve is composed of many different types of nerve fibre including '''general somatic efferent fibres''' supplying motor function to the muscles of the larynx, pharynx, palate and oesophagus; '''general visceral afferent fibres''' to the base of the tongue, pharynx and larynx; '''general visceral efferent fibres''' for parasympathetic supply of the thoracic and abdominal viscera; '''special visceral afferent fibres''' supplying taste to regions of the epiglottis and palate and finally '''general somatic afferent fibres''' to the external ear and the dura mater. The vagus nerve also supplies '''general somatic afferent fibres''' and '''special visceral afferent fibres''' to the root of the tongue.
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There are many functional components of the vagus nerve including the heart, larynx, pharynx and many other viscera. On clinical examination any changes related to gag reflexes, blood pressure or heart rate, changes in 'voice' or inspiratory dyspnoea may indicate a problem with the vagus nerve.

===Accessory nerve (XI)===
The accessory nerve is part of the group of cranial nerves responsible for innervation of structures derived from the branchial arches. It is also part of a group together with the glossopharyngeal and vagus nerves that passes through the '''jugular foramen''' which is termed the '''vagus group'''. The accessory nerve supplies structures related to the fourth branchial arch. The accessory nerve has cell bodies that are referred to as '''nucleus ambiguus''' and originate in the medulla oblongata. The cranial root of the accessory nerve actually contributes to the vagus nerve and to the striated muscles of the pharynx, larynx, palate and oesophagus.

However, the accessory nerve also contributes to the cervical spinal cord and spinal root through the '''foramen magnum''' providing innervation to muscles of the neck. The spinal root of the accessory nerve branches into the '''dorsal branch''' and the '''ventral branch'''. The dorsal branch innervates the brachiocephalicus, trapezius and omotransversarius muscles of the dorsal neck. The ventral branch innervates the sternocephalicus muscle.
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During clinical examination any difficulties in turning the neck or muscle atrophy around the dorsal and ventral neck may indicate a problem with the accessory nerve.

===Hypoglossal nerve (XII)===
The hypoglossal nerve is part of the group of cranial nerves responsible for the control of muscles of the head. It is in part a cervical nerve due to its caudal position on the [[Hindbrain - Anatomy & Physiology|brain stem]]. The nerve is composed of '''general somatic efferent fibres''' which control the intrinsic and extrinsic muscles of the tongue (together with other nerves including the lingual nerve, facial nerve, lingual branch of the glossopharyngeal nerve and the vagus nerve). The nucleus of the nerve is located within the medulla oblongata of the brain stem and it passes through the '''hypoglossal canal'''.
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During a clinical examination any deviation of the tongue may indicate a problem with this nerve. Deviation of the tongue is always to the side of the lesion.

==Cranial Nerve Summary/Revision Tables==
These tables are designed to be a revision aid and do not contain any specific details. Details regarding each nerve are in the written section above.
===Cranial Nerve Location and Routes===
A table summarising the cranial nerve location and route information in the section above has been included to summarise the key points for each cranial nerve. For the fibre type please see the Fibre Type section (heading 2 above) using the fibre type link in the table.

{| style="width:100%; height:200px" border="1"

! '''Nerve'''
! '''Attatchment to brain'''
! '''Exit Foramen'''
! '''[[#Cranial Nerve Fibre Types|Fibre Type]]'''
! '''Location of cell bodies'''
! '''Distribution'''

|-
| '''I - Olfactory'''
| Olfactory bulb
| Cribriform plate
| SVA
| Olfactory epithelium
| Olfactory epithelium
|-

| '''II - Optic'''
| Diencephalon (via optic chiasm)
| Optic canal
| SSA
| Retina
| Retina

|-
| '''III - Oculomotor'''
| Midbrain
| Orbital fissure
| GSE + GVE
| Oculomotor motor nucleus
Parasympathetic nucleus of oculomotor nerve
| Extraoccular mm.
Constrictor pupilli

|-
| '''IV - Trochlear'''
| Midbrain (dorsal)
| Orbital fissure
| GSE
| Trochlear nucleus
| Dorsal oblique mm.
|-

| '''V - Trigeminal'''
| Pons
| V1 - Orbital fissure
V2 - Round Foramen/Rostral alar foramen

V3 - Oval Foramen
| V1 - GSA
V2 - GSA

V3 - GSA & GSE
| V1 - Trigeminal gangion (GSA)
V2 - Trigeminal ganglion (GSA)

V3 - Trigeminal ganglion (GSA), Geniculate ganglion (SVA), Trigeminal motor nucleus (motor)
| V1 - Eye region
V2 - Upper jaw inc. teeth

V3 - mm. of arch 1, lower jaw, rostral 2/3 tongue

|-
| '''VI - Abducens'''
| Medulla oblongata
| Orbital fissure
| GSE
| Abducent nucleus
| Lateral rectus and retractor bulbi mm.
|-

|-
| '''VII - Facial'''
| Medulla oblongata
| Internal acoustic meatus/facial canal/stylomastoid foramen
| SVA + GVE + GSE + GSA
| Facial motor nucleus
Geniculate ganglion
| mm. of arch 2
Submaxillary and sublingual glands

Rostral 2/3 tongue
|-

|-
| '''VIII - Vestibulocochlear'''
| Medulla oblongata
| Internal acoustic meatus
| SSA
| Vestibular ganglion, spiral ganglion
| Maculae and cristae
|-

|-
| '''IX - Glossopharyngeal'''
| Medulla oblongata
| Jugular foramen/tympanooccipital fissure
| GSE GVA GVE GSA SVA
| Glossopharyngeal ganglion
Glossopharyngeal parasympathetic nucleus, nucleus ambiguus - mm. arch 3
| Carotid gland
Caudal 1/3 tongue
mm. of arch 3

Carotid body
|-

|-
| '''X - Vagus'''
| Medulla oblongata
| Jugular foramen/tympanooccipital fissure
| GSE GVA GVE SVA GSA
| Vagal ganglion - (amongst others)
Vagal parasympathetic nucleus, nucleus ambiguus
| Thoracic and abdominal organs
mm. of arches 4-6
Pharynx and larynx
External ear
|-

|-
| '''XI - Accessory'''
| Medulla oblongata
| Jugular foramen/tympanooccipital fissure
| GSE
| Nucleus ambiguus, accessory motor nucleus (cervical spinal cord)
| Trapezius m. etc
|-

|-
| '''XII - Hypoglossal'''
| Medulla oblongata
| Hypoglossal canal
| GSE
| Hypoglossal nucleus
| Tongue mm.
|-
|}

===Cranial Nerves Functions===
This table is designed to provide the basic function of each cranial nerve and has also been designed as a summary/revision aid.
{| border="1" cellpadding="7"
|-style="background:#B0E0E6; color:black"
!'''#'''
!'''Name'''
!'''Nuclei'''
!'''Function'''
|-
|'''I'''
| '''''Olfactory nerve'''''
|Anterior olfactory nucleus
| Transmits the sense of smell
|- style="background:#F0F8FF; color:black"
| '''II'''
| '''''Optic nerve'''''
| Lateral geniculate nucleus
| Transmits visual information to the brain
|-
| '''III''' || '''''Oculomotor nerve''''' || Oculomotor nucleus, Edinger-Westphal nucleus || Innervates the dorsal rectus, medial rectus, ventral rectus, and ventral oblique, which collectively perform most eye movements
|- style="background:#F0F8FF; color:black"
| '''IV'''
| '''''Trochlear nerve'''''
| Trochlear nucleus
| Innervates the superior oblique muscle, which depresses, pulls laterally, and intorts the eyeball
|-
| '''V''' || '''''Trigeminal nerve''''' || Principal sensory trigeminal nucleus, Spinal trigeminal nucleus, Mesencephalic trigeminal nucleus, Trigeminal motor nucleus || Receives sensation from the face and innervates the muscles of mastication
|- style="background:#F0F8FF; color:black"
| '''VI'''
| '''''Abducens nerve'''''
| Abducens nucleus
| Innervates the lateral rectus, which abducts the eye and the retractor bulbi which forces the third eyelid across the surface of the cornea as a protective mechanism.
|-
| '''VII''' || '''''Facial nerve''''' || Facial nucleus, Solitary nucleus, Superior salivary nucleus || Provides motor innervation to the muscles of facial expression and stapedius, receives the special sense of taste from the anterior 2/3 of the tongue, and provides secretomotor innervation to the salivary glands (except parotid) and the lacrimal gland
|- style="background:#F0F8FF; color:black"
|'''VIII'''
| '''''Vestibulocochlear nerve'''''
| Vestibular nuclei, Cochlear nuclei
| Senses sound, rotation and gravity (essential for balance & movement)
|-
| '''IX''' || '''''Glossopharyngeal nerve''''' || Nucleus ambiguus, Inferior salivary nucleus, Solitary nucleus || Receives taste from the posterior 1/3 of the tongue, provides secretomotor innervation to the parotid gland, and provides motor innervation to the stylopharyngeus
|- style="background:#F0F8FF; color:black"
| '''X'''
| '''''Vagus nerve'''''
| Nucleus ambiguus, Dorsal motor vagal nucleus, Solitary nucleus
| Supplies branchiomotor innervation to most laryngeal and pharyngeal muscles; provides parasympathetic fibers to nearly all thoracic and abdominal viscera down to the splenic flexure; and receives the special sense of taste from the epiglottis
|-
| '''XI''' || '''''Accessory nerve''''' || Nucleus ambiguus, Spinal accessory nucleus || Controls muscles of the neck and overlaps with functions of the vagus
|- style="background:#F0F8FF; color:black"
| '''XII'''
| '''''Hypoglossal nerve'''''
| Hypoglossal nucleus
| Provides motor innervation to the intrinsic muscles of the tongue and other glossal muscles
|}

==Learning Mnemonic==
There are various ways to memorise the cranial nerves including both the names of the actual nerves themselves and also their functions/type of nerve fibre. Here are some examples for the nerve names and also some for the type of nerve.
===Nerve Name Mnemonics===
====Mnemonic 1====
* '''O'''h (''O''lfactory I)
* '''O'''h (''O''ptic II)
* '''O'''h (''O''culomotor III)
* '''T'''o (''T''rochlear IV)
* '''T'''ouch (''T''rigeminal V)
* '''A'''nd (''A''bducens VI)
* '''F'''eel (''F''acial VII)
* '''A''' (''A''uditory/Vestibulocochlear VIII)
* '''G'''irl's (''G''lossopharyngeal IX)
* '''V'''ery (''V''agus X)
* '''S'''oft (''S''pinal/Accessory XI)
* '''H'''ands (''H''ypoglossal XII)
====Mnemonic 2====
* '''O'''h (''O''lfactory I)
* '''O'''nce (''O''ptic II)
* '''O'''ne (''O''culomotor III)
* '''T'''akes (''T''rochlear IV)
* '''T'''he (''T''rigeminal V)
* '''A'''natomy (''A''bducens VI)
* '''F'''inal (''F''acial VII)
* '''A''' (''A''uditory/Vestibulocochlear VIII)
* '''G'''ood (''G''lossopharyngeal IX)
* '''V'''acation (''V''agus X)
* '''S'''eems (''S''pinal/Accessory XI)
* '''H'''eavenly (''H''ypoglossal XII)
====Mnemonic 3====
* '''O'''nly (''O''lfactory I)
* '''O'''ffer (''O''ptic II)
* '''O'''nce (''O''culomotor III)
* '''T'''o (''T''rochlear IV)
* '''T'''ry (''T''rigeminal V)
* '''A'''nd (''A''bducens VI)
* '''F'''ind (''F''acial VII)
* '''V'''erdant (''A''uditory/Vestibulocochlear VIII)
* '''G'''reen (''G''lossopharyngeal IX)
* '''V'''erges (''V''agus X)
* '''A'''nd (''S''pinal/Accessory XI)
* '''H'''edges (''H''ypoglossal XII)

===Nerve Type Mnemonics===
For the mnemonic below ''S = sensory'', ''M = motor'' and ''B = both'' (sensory and motor).
* '''S'''ome
* '''S'''ay
* '''M'''arry
* '''M'''oney
* '''B'''ut
* '''M'''y
* '''B'''rother
* '''S'''ays
* '''B'''ig
* '''B'''usiness
* '''M'''akes
* '''M'''oney

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[[Category:Nervous System - Anatomy & Physiology]]
[[Category:A&P Done]]

Cranial Nerves - Anatomy & Physiology

2022-10-27T19:29:07Z

Roytwv:

{{OpenPagesTop}}
[[File:Brain human normal inferior view with labels en.svg|thumb|right|400px|Ventral brain showing labelled cranial nerves, WikiCommons]]
==Introduction==
Cranial nerves are those nerves which arise from the brain and [[Hindbrain - Anatomy & Physiology|brain stem]] rather than the spinal cord. Nerves arising from the spinal cord are the [[PNS Structure - Anatomy & Physiology|spinal nerves]]. There are 12 pairs of cranial nerves and these pairs of nerves passage through [[Skull and Facial Muscles - Anatomy & Physiology|foramina in the skull]], either individually or in groups. Cranial nerves are traditionally referred to by Roman numerals and these numerals begin cranially and run caudally.
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The most cranial nerve is the '''Olfactory nerve (I)''' which runs from the nasal cavity through to the olfactory bulb. The next most cranial is the '''Optic nerve (II)''' which runs from the eyes to the [[Forebrain - Anatomy & Physiology#Thalamus|thalamus]]. Cranial nerves III to XII all exit from the brain stem and innervate the head, neck and organs in the thorax and abdomen. In order of most cranial to caudal, these include the '''Oculomotor nerve (III)''', the '''Trochlear nerve (IV)''', the '''Trigeminal nerve (V)''', the '''Abducens nerve (VI)''', the '''Facial nerve (VII)''', the '''Vestibulocochlear nerve (VIII)''', the '''Glossopharyngeal nerve (IX)''', the '''Vagus nerve (X)''', the '''Accessory nerve (XI)''' and the '''Hypoglossal nerve (XII)'''.
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Many of the cranial nerves with nuclei within the brain stem contain sensory and motor neurone components. The sensory fibre components have their cell bodies located in ganglia outside the central nervous system and the motor fibre element have their cell bodies within the central nervous system.

==Cranial Nerve Fibre Types==
Prior to a full explanation of each cranial nerve function, physiology, anatomy and particularly composition, the numerous types of nerve fibre found in cranial nerves must be explained to ensure that the following can be better understood.

Nerve fibres can undertake numerous roles within the body and their function is dictated by what type of fibre the nerve is composed of. A classification scheme is used to describe the type of fibres found within the cranial nerves and therefore provides a better understanding of the function and composition of that particular nerve. Below is a brief outline of this nerve fibre classification.

===Afferent Fibres - Sensory===
====General Somatic Afferent (GSA)====
This type of fibre is used in the majority of basic senses including temperature, touch and [[Pain|pain]]. These fibres mainly supply sensation to various areas of the head including to the skin and face via the trigeminal nerve (cranial nerve V); to the skin of the [[Ear - Anatomy & Physiology#Outer_Ear|external ear]] via the trigeminal nerve (cranial nerve V), the facial nerve (cranial nerve VII), the glossopharyngeal nerve (cranial nerve IX) and via the vagus nerve (cranial nerve X); to the mucosae of the [[Oral Cavity Overview - Anatomy & Physiology|oral cavity]] via the trigeminal nerve (cranial nerve V) and to the [[Meninges - Anatomy & Physiology|meningies]] of the brain via the trigeminal nerve (cranial nerve V) and the vagus nerve (cranial nerve X).

:'''Skin Sensation Example'''

:''Sensory cortex —→ Thalamus —→ Trigeminal nuclei —→ Trigeminal ganglion —→ Skin etc.''

====Special Somatic Afferent (SSA)====
The special signifies that this fibre type is found in nerves related to the special senses which include [[Eye - Anatomy & Physiology#Vision|vision]] and [[Ear - Anatomy & Physiology#Function_-_Hearing|hearing]]. This therefore relates to the optic nerves (cranial nerve II) and the auditory/vestibular systems which are the vestibulocochlear nerves (cranial nerve VIII).

:'''Vision Example'''

:''Occipital cortex —→ Thalamus MGN —→ Rostral colliculus/Retinal ganglion cell —→ Bipolar cell —→ [[Eye - Anatomy & Physiology|Vision]]''

:'''Hearing Example'''

:''Temporal cortex —→ Thalamus MGN —→ Caudal colliculus and hindbrain —→ Spiral ganglion —→ [[Ear - Anatomy & Physiology|Hearing]]''

====General Visceral Afferent (GVA)====
This fibre type is commonly found in sensory nerves to organs and to sensory tissues related to chemicals. These include fibres found in the glossopharyngeal nerves (cranial nerve IX) and the vagus nerves (cranial nerve X).

:'''Organ Sensory Example'''

:''Sensory cortex —→ Thalamus —→ Cranial nerve nuculi —→ Nerve ganglion —→ Organs etc.''

====Special Visceral Afferent (SVA)====
This fibre type is found again in special sense organs related to the sensing of chemicals and therefore including [[Gustatory System - Anatomy & Physiology|taste]] and [[olfaction]]. The olfactory sense relates to the olfactory nerve (cranial nerve I) and the taste senses relate to the facial nerve (cranial nerve VII), the glossopharyngeal nerve (cranial nerve IX) and the vagus nerve (cranial nerve X). The sense of taste is performed by the gustatory organ which are cells located in gustatory papillae in the mucous membrane of the dorsal side of the tongue. Taste buds can also be found in the soft palate, pharynx, larynx, lips and cheeks.

:'''Olfaction Example'''

:''Piriform cortex —→ Olfactory tubercle —→ Olfactory Bulb —→ [[Nose - Anatomy & Physiology|Smell]]''

:'''Taste Example'''

:''Sensory cortex —→ Thalamus —→ Hindbrain (VII, IX, X) —→ Ganglion —→ [[Gustatory System - Anatomy & Physiology|Taste]]''

===Efferent Fibres - Motor===
====General Somatic Efferent (GSE)====
This type of nerve fibre is mainly found in nerves supplying [[Muscles - Anatomy & Physiology#Skeletal_Muscle|skeletal muscles]]. Motor fibres such as these undertake numerous roles within the body such as control over the external ocular muscles via the oculomotor nerve (cranial nerve III), the trochlear nerve (cranial nerve IV) and the abducent nerve (cranial nerve VI); or for example the muscles around the dorsal and ventral neck including the brachiocephalicus, trapezius, omotransversarius and the sternocephalicus which are all supplied by the accessory nerve (cranial nerve XI).

:'''Motor Nerve Innervation Example'''

:''Motor cortex —→ Motor nuculi —→ Muscle''

====General Visceral Efferent (GVE)====
This type of nerve fibre is found in nerves supplying [[Muscles - Anatomy & Physiology#Smooth_Muscle|smooth muscle]], [[Muscles - Anatomy & Physiology#Cardiac_Muscle|cardiac muscle]] and glands. Sympathetic innervation for this type of nerve fibre comes directly from the cranial cervical ganglion. However, parasympathetic innervation comes from several cranial nerves including the oculomotor nerve (cranial nerve III), the vestibulocochlear nerve (cranial nerve VIII), the glossopharyngeal nerve (cranial nerve IX) and the vagus nerve (cranial nerve X). Examples of where this type of fibre functions include the pupillary sphinter via the oculomotor nerve, glands of the nasal/oral cavity via the vestibulocochlear and glossopharyngeal nerves and thoracic/abdominal viscera via the vagus nerve.

:'''Gland Innervation Example'''

:''Brainstem —→ Parasympathetic nuculi —→ Parasympathetic ganglion —→ Gland etc.''

==Cranial Nerves==
There are three main groups of cranial nerves; special senses, innervation of the head muscles and innervation of structures originating from branchial arches. The special senses cranial nerves include the olfactory, ocular and vestibulocochlear. Cranial nerves related to the innervation of the head muscles include the oculomotor, trochlear, abducens and the hypoglossal nerves. Cranial nerves related to innervation of structures originating from branchial arches include the trigeminal, facial, glossopharyngeal, vagus and accessory nerves.

===Olfactory Nerve (I)===
Olfaction is part of the special senses cranial nerve group and represents the chemical senses of olfaction (smell) and gustation (taste). When chemical substances interact with our bodies they stimulate special sensory cells which in turn generate an action potential. The resultant impulse is sent to the brain via sensory afferent fibres and it is these fibres that represent the olfactory cranial nerve. Note: an action potential is only generated where a special sensory cell for that particular chemical substance exists. If no sensory cell exists, that chemical substance will go undetected. The olfactory neurosensory cells are found within the olfactory epithelium. The olfactory epithelium contains cilia on the surface of the cells to increase the surface area for chemical interactions.
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The olfactory nerve runs to the olfactory bulb which is found within the [[Forebrain - Anatomy & Physiology#Olfactory_Bulb|telencephalon]]. The olfactory nerve is a sensory nerve and is composed of many '''Special Visceral Afferent''' fibres. The fibres are formed into bundles that are referred to as 'Olfactory filaments'. The olfactory nerve passes through the [[Skull and Facial Muscles - Anatomy & Physiology#Ethmoid Bone (os ethmoidale)|'''Cribiform plate''']] and is surrounded by meningeal sheets including the [[Meninges - Anatomy & Physiology#Subarachnoid_Space|sub-arachnoid space]]. Therefore the route of the olfactory nerve represents a potential site for an infection to track towards the brain. Injury of this nerve can lead to 'anosmia', or loss of smell.
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The olfactory organ in dogs is extremely well developed and species such as canines use olfaction to orientate themselves in an environment in a way that humans do not. Olfactory cells are continuously replaced and are only viable sensory cells for between 30 - 60 days. This point is of importance as this is the only area in which nerve cells are able to be replaced or regenerated in adult animals and this area is now under research at Cambridge University for the treatment of damaged nerves and/or nerve disorders in nerves other than those involved in olfaction.

===Optic Nerve (II)===
The optic nerve is part of the special senses cranial nerves and represents the connection between the receptor cells of the [[Eye - Anatomy & Physiology#The Wall (retina, uvea and sclera)|retina]] and the [[Forebrain - Anatomy & Physiology|diencephalon]]. The optic nerve is a sensory nerve and is composed of '''Special Somatic Afferent fibres'''. Optic nerve axons pass from the optic disc of the retina to the brain, entering the skull via the [[Skull and Facial Muscles - Anatomy & Physiology#Sphenoid Bone (os_sphenoidale)|'''optic canal''']]. The majority of axons decussate at the [[Skull and Facial Muscles - Anatomy & Physiology#Sphenoid Bone (os_sphenoidale)|'''optic chiasm''']] before continuing as the optic tracts.
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The optic nerve can be examined clinically via a [[Neurological Eye Examination - Horse#Menace Response|menace response]] and anopsia (loss of vision) can be seen in injury.

===Oculomotor nerve (III)===
The oculomotor nerve is part of the group of cranial nerves responsible for innervating the [[Skull and Facial Muscles - Anatomy & Physiology#Facial_Muscles|muscles of the head]]. The nerves originate from the ventral [[Midbrain - Anatomy & Physiology|midbrain]] and is a motor nerve. It is composed of '''general somatic efferent fibres''' and '''general visceral efferent fibres'''. The general somatic efferent fibres of the oculomotor nerve are responsible for the motor function of four of the six [[Eye - Anatomy & Physiology#Around_the_Eye|external muscles of the eyeball]]; the 'dorsal rectus', 'medial rectus', 'ventral rectus', 'ventral oblique' and 'levator of the upper eyelid'. The general visceral efferent fibres of the oculomotor nerve control the 'sphincter pupillae' muscle (alters pupillary diameter) and the 'ciliaris' muscle (alters curvature of the lens).
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The oculomotor nerve has a pre-ganglionic nucleus in the midbrain and the nerve passes through the [[Skull_and_Facial_Muscles_-_Anatomy_%26_Physiology#Major_Foramen_and_Canals|'''orbital fissure''']], along with the trochlear, abducens and opthalmic branch (V1) of the trigeminal nerve. It synapses in the ciliary ganglion of the eye. During a clinical examination, horizontal eye movements (strabismus) or an absent [[Neurological_Eye_Examination_-_Horse#The_pupillary_light_reflex_(PLR)|pupillary light reflex (PLR)]] may indicate a problem.

===Trochlear nerve (IV)===
The trochlear nerve is part of the cranial nerve group responsible for innervation of the muscles of the head. The trochlear nerve originates from the dorsal mid-brain and is a motor nerve. It is composed of '''general somatic efferent fibres''' and is the smallest of the cranial nerves. The nerve is specifically responsible for the 'dorsal oblique muscle' muscle of the eye and also passes through the [[Skull and Facial Muscles - Anatomy & Physiology#Major Foramen and Canals|'''orbital fissure''']].
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During a clinical examination, a dorso-lateral strabismus may indicate a problem with this nerve.

===Trigeminal nerve (V)===
The trigeminal nerve is part of the cranial nerve group responsible for innervation of structures originating from branchial arches. The trigeminal nerve nuclei are in the area of the pons and medulla oblongata and it is the nerve of the 1st branchial arch. In general terms the trigeminal represents the sensory nerve of the head but also provides motor fibres to structures also associated with the 1st branchial arch. There are three primary branches of the trigeminal nerve; the '''Opthalmic nerve (V1)''', the ''' Maxillary nerve (V2)''' and the '''Mandibular nerve (V3)'''.

====Ophthalmic nerve (V1)====
The ophthalmic nerve is a sensory nerve composed of '''general somatic afferent fibres''' and passes through the [[Skull and Facial Muscles - Anatomy & Physiology#Major Foramen and Canals|'''orbital fissure''']]. As it enters the orbit of the eye it splits further into the '''lacrimal nerve''', the '''frontal nerve''', the '''nasociliary nerve''' and the '''infratrochlear nerve'''. Therefore the nerve supplies sensory fibres to many components of the orbit.

====Maxillary nerve (V2)====
The maxillary nerve is a sensory nerve composed of '''general somatic afferent fibres'''. The maxillary nerve passes through the [[Skull and Facial Muscles - Anatomy & Physiology#Major Foramen and Canals|'''round foramen''']] and the [[Skull and Facial Muscles - Anatomy & Physiology#Major Foramen and Canals|'''alar canal''']]. It also runs across the wall of the '''pterygopalatine fossa''' and enters the '''infraorbital canal''' via the '''maxillary foramen'''. Whilst in the infraorbital canal, the maxillary nerve branch then branches further into the '''infraorbital nerve''' which supplies sensory fibres to the teeth. On exiting the infraorbital canal via the infraorbital foramen, the maxillary nerve branches again into the '''zygomatic nerve''' which supplies sensory fibres to the horn and to the '''pterygopalatine nerve''' supplying sensory fibres to the palate.

====Mandibular nerve (V3)====
The mandibular nerve is a mixed sensory '''general somatic afferent fibres''' and motor '''general somatic efferent''' nerves. The mandibular nerve passes through the [[Skull_and_Facial_Muscles_-_Anatomy_%26_Physiology#Major_Foramen_and_Canals|'''oval foramen''']]. It provides motor branches to the [[Mastication|masticatory muscles]], the [[Larynx - Anatomy & Physiology#Intrinsic Musculature|ventral throat]] and [[Tongue - Anatomy & Physiology#Muscles|muscles of the palate]]. The mandibular nerve further branches into the '''masticatory nerve''', the '''masseteric nerve''' and the '''temporal nerve'''. The mandibular nerve provides sensory branches called the '''buccal nerve''', the '''auriculotemporal nerve''', and then itself divides into two smaller branches; the '''lingual nerve''' and the '''inferior alveolar nerve'''. The '''lingual nerve''' receives sensory fibres to the rostral 2/3 of the tongue and also connects some sensory taste fibres to parasympathetic salivary glands via the [[Tongue - Anatomy & Physiology#Innervation|'''chorda tympani''']]. The lingual branch of the glossopharyngeal nerve supplies sensory taste fibres to the caudal 1/3 of the tongue, while the facial nerve supplies sensory taste fibres to the rostral 2/3 of the tongue.

===Abducent nerve (VI)===
The abducent nerve is part of the cranial nerve group responsible for innervation of the muscles of the head. The abducent nerve originates from the medulla oblongata and is a motor nerve. It is composed of '''general somatic efferent fibres''' which are responsible for controlling the 'lateral rectus' muscle and the 'retractor bulbi' muscle of the eye. The nerve passes through the '''orbital fissure''' and can be found within the same layer of the meninges as the opthalmic branch (V1) of the trigeminal nerve (V).
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During a clinical examination, medial deviation strabismus may indicate a problem with this nerve.

===Facial nerve (VII)===
The facial nerve is part of the cranial nerve group responsible for the innervation of structures originating from the branchial arches. It originates from the medulla oblongata and from the second branchial arch. It has a common dura sheet with the opthalmic (V1) branch of the trigeminal nerve. The facial nerve is of a mixed composite and is made up of a number of different fibre types. It has a '''general somatic efferent fibre''' within the ear canal, a '''general visceral efferent fibre''' acting under parasympathetic control to some salivary glands, lacrimal glands, nasal cavity and palate, a '''special visceral afferent fibre''' providing taste to the rostral 2/3 of the tongue and finally it has a '''general somatic efferent fibre''' supplying motor function to the muscles of facial expression.
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The facial nerve enters the petrosal bone via the [[Skull and Facial Muscles - Anatomy & Physiology#Temporal Bone (os_temporale)|'''internal acoustic meatus''']] along with the vestibulocochlear nerve. The facial nerve also runs inside the '''facial canal'''. There are a number of intermediate branches which separate from the main facial nerve inside the facial canal including the '''greater petrosal nerve''', the '''stapedial nerve''' (motor) and the '''chorda tympani'''. These then emerges via the [[Skull and Facial Muscles - Anatomy & Physiology#Major Foramen and Canals|'''stylomastoid foramen''']] at the caudoventral aspect of the skull. The chorda tympani of the facial nerve represents the '''special visceral afferent fibre''' supplying taste to the rostral 2/3 of the tongue.
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There are also numerous external branches of the facial nerve once the facial nerve has left the facial canal. These include the '''internal auricular nerve''', the '''auriculopalpebral nerve''', the '''rostral auricular nerve''', the '''palpebral nerve''', the '''dorsal buccolabial nerve''', the '''ventral buccolabial nerve''', the '''ramus colli''', the '''digastric nerve''', the '''stylohoid nerve''' and the '''caudal auricular nerve'''.
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The facial nerve supplies motor innervation to the muscles of facial expression. These are superficial flat, thin muscles that originate from bony areas of fascia and then radiate out around the skin. They may also often from sphincters such as around the mouth and eye.
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During a clinical examination any facial paralysis, drooling or abscence of blinking may indicate a problem with the facial nerve.

===Vestibulocochlear nerve (VIII)===
The vestibulocochlear nerve is part of the special senses group of cranial nerves and is made up of two components; the vestibular nerve and the cochlear nerve. The vestibular nerve is responsible for balance whilst the cochlear nerve is responsible for hearing. The nerves send impulses from the inner ear which contains the [[Ear - Anatomy & Physiology#Vestibular Receptors and Balance|vestibular apparatus]] and [[Ear - Anatomy & Physiology#The Cochlea|cochlea]]. The vestibulocochlear nerve is a sensory nerve made up of '''special somatic afferent fibres'''. It passes through the '''internal acoustic meatus''' and into the '''petrosal bone'''. The facial nerve also takes this route.
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Clinical problems with the vestibulocochlear nerve would be indicated on examination by changes in hearing and/or horizontal and vertical eye movements (strabismus and [[Vestibular System Examination|nystagmus]]). A head tilt is also associated with this nerve.

===Glossopharyngeal nerve (IX)===
The glossopharyngeal nerve is part of the group of cranial nerves responsible for innervation of structures derived from the branchial arches. This nerve innervates structures related to the third branchial arch. It is also part of a group together with the vagus and accessory nerves that passes through the '''jugular foramen''' which is termed the '''vagus group'''. The glossopharyngeal nerve has cell bodies that are referred to as '''nucleus ambiguus'''. The glossopharyngeal nerve originates from the medulla oblongata and has several branches including the '''pharyngeal nerve''', the '''lingual nerve''' and the '''tympanic branches'''.
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The glossopharyngeal nerve is composed of many fibre types including '''general somatic efferent fibres''' that innervate the stylopharyngeus muscle; the '''general visceral afferent fibres''' that provide sensory information from the carotid body, the pharynx and the middle ear; the '''general visceral efferent fibres''' that provide parasympathetic innervation to the parotid and zygomatic salivary glands; the '''special visceral afferent fibres''' that provide taste caudal to the tongue and finally the '''general somatic afferent fibres''' that provide sensory information from the external ear.
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The '''lingual branch''' of the glossopharyngeal nerve provides '''general somatic afferent fibres''' and '''special visceral afferent fibres''' to the caudal 1/3 of the tongue.
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On clinical examination, choking or dysphagia as a result of malfunctioning or absent pharyngeal reflexes would indicate a problem with the glossopharyngeal nerve.

===Vagus nerve (X)===
The vagus nerve is part of the group of cranial nerves responsible for innervation of structures derived from the branchial arches. It is also part of a group together with the glossopharyngeal and accessory nerves that passes through the '''jugular foramen''' which is termed the '''vagus group'''. The vagus nerve innervates structures related to the fourth branchial arch. The vagus nerve has cell bodies that are referred to as '''nucleus ambiguus'''.
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The vagus nerve is composed of many different types of nerve fibre including '''general somatic efferent fibres''' supplying motor function to the muscles of the larynx, pharynx, palate and oesophagus; '''general visceral afferent fibres''' to the base of the tongue, pharynx and larynx; '''general visceral efferent fibres''' for parasympathetic supply of the thoracic and abdominal viscera; '''special visceral afferent fibres''' supplying taste to regions of the epiglottis and palate and finally '''general somatic afferent fibres''' to the external ear and the dura mater. The vagus nerve also supplies '''general somatic afferent fibres''' and '''special visceral afferent fibres''' to the root of the tongue.
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There are many functional components of the vagus nerve including the heart, larynx, pharynx and many other viscera. On clinical examination any changes related to gag reflexes, blood pressure or heart rate, changes in 'voice' or inspiratory dyspnoea may indicate a problem with the vagus nerve.

===Accessory nerve (XI)===
The accessory nerve is part of the group of cranial nerves responsible for innervation of structures derived from the branchial arches. It is also part of a group together with the glossopharyngeal and vagus nerves that passes through the '''jugular foramen''' which is termed the '''vagus group'''. The accessory nerve supplies structures related to the fourth branchial arch. The accessory nerve has cell bodies that are referred to as '''nucleus ambiguus''' and originate in the medulla oblongata. The cranial root of the accessory nerve actually contributes to the vagus nerve and to the striated muscles of the pharynx, larynx, palate and oesophagus.

However, the accessory nerve also contributes to the cervical spinal cord and spinal root through the '''foramen magnum''' providing innervation to muscles of the neck. The spinal root of the accessory nerve branches into the '''dorsal branch''' and the '''ventral branch'''. The dorsal branch innervates the brachiocephalicus, trapezius and omotransversarius muscles of the dorsal neck. The ventral branch innervates the sternocephalicus muscle.
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During clinical examination any difficulties in turning the neck or muscle atrophy around the dorsal and ventral neck may indicate a problem with the accessory nerve.

===Hypoglossal nerve (XII)===
The hypoglossal nerve is part of the group of cranial nerves responsible for the control of muscles of the head. It is in part a cervical nerve due to its caudal position on the [[Hindbrain - Anatomy & Physiology|brain stem]]. The nerve is composed of '''general somatic efferent fibres''' which control the intrinsic and extrinsic muscles of the tongue (together with other nerves including the lingual nerve, facial nerve, lingual branch of the glossopharyngeal nerve and the vagus nerve). The nucleus of the nerve is located within the medulla oblongata of the brain stem and it passes through the '''hypoglossal canal'''.
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During a clinical examination any deviation of the tongue may indicate a problem with this nerve. Deviation of the tongue is always to the side of the lesion.

==Cranial Nerve Summary/Revision Tables==
These tables are designed to be a revision aid and do not contain any specific details. Details regarding each nerve are in the written section above.
===Cranial Nerve Location and Routes===
A table summarising the cranial nerve location and route information in the section above has been included to summarise the key points for each cranial nerve. For the fibre type please see the Fibre Type section (heading 2 above) using the fibre type link in the table.

{| style="width:100%; height:200px" border="1"

! '''Nerve'''
! '''Attatchment to brain'''
! '''Exit Foramen'''
! '''[[#Cranial Nerve Fibre Types|Fibre Type]]'''
! '''Location of cell bodies'''
! '''Distribution'''

|-
| '''I - Olfactory'''
| Olfactory bulb
| Cribriform plate
| SVA
| Olfactory epithelium
| Olfactory epithelium
|-

| '''II - Optic'''
| Diencephalon (via optic chiasm)
| Optic canal
| SSA
| Retina
| Retina

|-
| '''III - Oculomotor'''
| Midbrain
| Orbital fissure
| GSE + GVE
| Oculomotor motor nucleus
Parasympathetic nucleus of oculomotor nerve
| Extraoccular mm.
Constrictor pupilli

|-
| '''IV - Trochlear'''
| Midbrain (dorsal)
| Orbital fissure
| GSE
| Trochlear nucleus
| Dorsal oblique mm.
|-

| '''V - Trigeminal'''
| Pons
| V1 - Orbital fissure
V2 - Round Foramen/Rostral alar foramen

V3 - Oval Foramen
| V1 - GSA
V2 - GSA

V3 - GSA & GSE
| V1 - Trigeminal gangion (GSA)
V2 - Trigeminal ganglion (GSA)

V3 - Trigeminal ganglion (GSA), Geniculate ganglion (SVA), Trigeminal motor nucleus (motor)
| V1 - Eye region
V2 - Upper jaw inc. teeth

V3 - mm. of arch 1, lower jaw, rostral 2/3 tongue

|-
| '''VI - Abducens'''
| Medulla oblongata
| Orbital fissure
| GSE
| Abducent nucleus
| Lateral rectus and retractor bulbi mm.
|-

|-
| '''VII - Facial'''
| Medulla oblongata
| Internal acoustic meatus/facial canal/stylomastoid foramen
| SVA + GVE + GSE + GSA
| Facial motor nucleus
Geniculate ganglion
| mm. of arch 2
Submaxillary and sublingual glands

Rostral 2/3 tongue
|-

|-
| '''VIII - Vestibulocochlear'''
| Medulla oblongata
| Internal acoustic meatus
| SSA
| Vestibular ganglion, spiral ganglion
| Maculae and cristae
|-

|-
| '''IX - Glossopharyngeal'''
| Medulla oblongata
| Jugular foramen/tympanooccipital fissure
| GSE GVA GVE GSA SVA
| Glossopharyngeal ganglion
Glossopharyngeal parasympathetic nucleus, nucleus ambiguus - mm. arch 3
| Carotid gland
Caudal 1/3 tongue
mm. of arch 3

Carotid body
|-

|-
| '''X - Vagus'''
| Medulla oblongata
| Jugular foramen/tympanooccipital fissure
| GSE GVA GVE SVA GSA
| Vagal ganglion - (amongst others)
Vagal parasympathetic nucleus, nucleus ambiguus
| Thoracic and abdominal organs
mm. of arches 4-6
Pharynx and larynx
External ear
|-

|-
| '''XI - Accessory'''
| Medulla oblongata
| Jugular foramen/tympanooccipital fissure
| GSE
| Nucleus ambiguus, accessory motor nucleus (cervical spinal cord)
| Trapezius m. etc
|-

|-
| '''XII - Hypoglossal'''
| Medulla oblongata
| Hypoglossal canal
| GSE
| Hypoglossal nucleus
| Tongue mm.
|-
|}

===Cranial Nerves Functions===
This table is designed to provide the basic function of each cranial nerve and has also been designed as a summary/revision aid.
{| border="1" cellpadding="7"
|-style="background:#B0E0E6; color:black"
!'''#'''
!'''Name'''
!'''Nuclei'''
!'''Function'''
|-
|'''I'''
| '''''Olfactory nerve'''''
|Anterior olfactory nucleus
| Transmits the sense of smell
|- style="background:#F0F8FF; color:black"
| '''II'''
| '''''Optic nerve'''''
| Lateral geniculate nucleus
| Transmits visual information to the brain
|-
| '''III''' || '''''Oculomotor nerve''''' || Oculomotor nucleus, Edinger-Westphal nucleus || Innervates the dorsal rectus, medial rectus, ventral rectus, and ventral oblique, which collectively perform most eye movements
|- style="background:#F0F8FF; color:black"
| '''IV'''
| '''''Trochlear nerve'''''
| Trochlear nucleus
| Innervates the superior oblique muscle, which depresses, pulls laterally, and intorts the eyeball
|-
| '''V''' || '''''Trigeminal nerve''''' || Principal sensory trigeminal nucleus, Spinal trigeminal nucleus, Mesencephalic trigeminal nucleus, Trigeminal motor nucleus || Receives sensation from the face and innervates the muscles of mastication
|- style="background:#F0F8FF; color:black"
| '''VI'''
| '''''Abducens nerve'''''
| Abducens nucleus
| Innervates the lateral rectus, which abducts the eye and the retractor bulbi which forces the third eyelid across the surface of the cornea as a protective mechanism.
|-
| '''VII''' || '''''Facial nerve''''' || Facial nucleus, Solitary nucleus, Superior salivary nucleus || Provides motor innervation to the muscles of facial expression and stapedius, receives the special sense of taste from the anterior 2/3 of the tongue, and provides secretomotor innervation to the salivary glands (except parotid) and the lacrimal gland
|- style="background:#F0F8FF; color:black"
|'''VIII'''
| '''''Vestibulocochlear nerve'''''
| Vestibular nuclei, Cochlear nuclei
| Senses sound, rotation and gravity (essential for balance & movement)
|-
| '''IX''' || '''''Glossopharyngeal nerve''''' || Nucleus ambiguus, Inferior salivary nucleus, Solitary nucleus || Receives taste from the posterior 1/3 of the tongue, provides secretomotor innervation to the parotid gland, and provides motor innervation to the stylopharyngeus
|- style="background:#F0F8FF; color:black"
| '''X'''
| '''''Vagus nerve'''''
| Nucleus ambiguus, Dorsal motor vagal nucleus, Solitary nucleus
| Supplies branchiomotor innervation to most laryngeal and pharyngeal muscles; provides parasympathetic fibers to nearly all thoracic and abdominal viscera down to the splenic flexure; and receives the special sense of taste from the epiglottis
|-
| '''XI''' || '''''Accessory nerve''''' || Nucleus ambiguus, Spinal accessory nucleus || Controls muscles of the neck and overlaps with functions of the vagus
|- style="background:#F0F8FF; color:black"
| '''XII'''
| '''''Hypoglossal nerve'''''
| Hypoglossal nucleus
| Provides motor innervation to the intrinsic muscles of the tongue and other glossal muscles
|}

==Learning Mnemonic==
There are various ways to memorise the cranial nerves including both the names of the actual nerves themselves and also their functions/type of nerve fibre. Here are some examples for the nerve names and also some for the type of nerve.
===Nerve Name Mnemonics===
====Mnemonic 1====
* '''O'''h (''O''lfactory I)
* '''O'''h (''O''ptic II)
* '''O'''h (''O''culomotor III)
* '''T'''o (''T''rochlear IV)
* '''T'''ouch (''T''rigeminal V)
* '''A'''nd (''A''bducens VI)
* '''F'''eel (''F''acial VII)
* '''A''' (''A''uditory/Vestibulocochlear VIII)
* '''G'''irl's (''G''lossopharyngeal IX)
* '''V'''ery (''V''agus X)
* '''S'''oft (''S''pinal/Accessory XI)
* '''H'''ands (''H''ypoglossal XII)
====Mnemonic 2====
* '''O'''h (''O''lfactory I)
* '''O'''nce (''O''ptic II)
* '''O'''ne (''O''culomotor III)
* '''T'''akes (''T''rochlear IV)
* '''T'''he (''T''rigeminal V)
* '''A'''natomy (''A''bducens VI)
* '''F'''inal (''F''acial VII)
* '''A''' (''A''uditory/Vestibulocochlear VIII)
* '''G'''ood (''G''lossopharyngeal IX)
* '''V'''acation (''V''agus X)
* '''S'''eems (''S''pinal/Accessory XI)
* '''H'''eavenly (''H''ypoglossal XII)
====Mnemonic 3====
* '''O'''nly (''O''lfactory I)
* '''O'''ffer (''O''ptic II)
* '''O'''nce (''O''culomotor III)
* '''T'''o (''T''rochlear IV)
* '''T'''ry (''T''rigeminal V)
* '''A'''nd (''A''bducens VI)
* '''F'''ind (''F''acial VII)
* '''V'''erdant (''A''uditory/Vestibulocochlear VIII)
* '''G'''reen (''G''lossopharyngeal IX)
* '''V'''erges (''V''agus X)
* '''A'''nd (''S''pinal/Accessory XI)
* '''H'''edges (''H''ypoglossal XII)

===Nerve Type Mnemonics===
For the mnemonic below ''S = sensory'', ''M = motor'' and ''B = both'' (sensory and motor).
* '''S'''ome
* '''S'''ay
* '''M'''arry
* '''M'''oney
* '''B'''ut
* '''M'''y
* '''B'''rother
* '''S'''ays
* '''B'''ig
* '''B'''usiness
* '''M'''akes
* '''M'''oney

==Webinars==
'''[https://www.thewebinarvet.com/webinar/clinical-decision-making-in-neurology?utm_source=wikivet&utm_medium=link&utm_campaign=Cranial_Nerves Clinical Decision Making in Neurology]'''

{{Learning
|videos = [[Video: Lateral surface of the head of the dog potcast 2|Lateral surface of the head of the dog potcast 2]]<br>[[Video: Canine orbit and sagittal section of the canine head|Canine orbit and sagittal section of the canine head]]<br>[[Video: Lateral surface of the head of the dog potcast 3|Lateral surface of the head of the dog potcast]]<br>[[Video: Lateral surface of the head of the dog potcast 5|Lateral surface of the head of the dog potcast 5]]<br>
}}
<rss max="10" highlight="none">https://www.thewebinarvet.com/urogenital-and-reproduction/webinars/feed</rss>
[[Category:Nervous System - Anatomy & Physiology]]
[[Category:A&P Done]]

Heart Structure - Anatomy & Physiology

2022-10-27T19:27:18Z

Roytwv:

{{OpenPagesTop}}
==Structure of the Heart==
[[Image:Aspinall Slide7.JPG|thumb|right|350px|<small>Image from [http://www.elsevierhealth.co.uk/veterinary-nursing/spe-60136/ Aspinall, The Complete Textbook of Veterinary Nursing], Elsevier Health Sciences, ''All rights reserved''</small>]]
[[Image:Aspinall Slide8.JPG|thumb|right|350px|<small>Image from [http://www.elsevierhealth.co.uk/veterinary-nursing/spe-60136/ Aspinall, The Complete Textbook of Veterinary Nursing], Elsevier Health Sciences, ''All rights reserved''</small>]]
===Position and Shape of the Heart===

The heart is located in the thoracic cavity in between the [[Lungs - Anatomy & Physiology|lungs]], 60% of it lying to the left of the median plane. The heart’s lateral projection extends from [[Ribs and Sternum - Anatomy & Physiology|rib]] 3 to 6. Most of the heart’s surface is covered by the [[Lungs - Anatomy & Physiology|lungs]] and in juveniles it is bordered cranially by the [[Thymus - Anatomy & Physiology|thymus]]. Caudally the heart extends as far as the [[Diaphragm - Anatomy & Physiology|diaphragm]]. Variations in position and size exist among individuals depending on species, breed, age, fitness and pathology. Roughly speaking, the heart is responsible for about 0.75% of the bodyweight.

The heart is cone-shaped, with a broad base at the top from which the large blood vessels enter and exit. The tip, known as the apex, points downwards and lies close to the [[Ribs and Sternum - Anatomy & Physiology|sternum]]. The longitudinal axis of the heart is tilted to varying degrees depending on the species resulting in the base facing craniodorsally and the apex caudoventrally.

The heart has a right and left lateral surface, which meet cranially at the right ventricular border and caudally at the left ventricular border. The auricles of the atria are visible on the left side, surrounding the root of the aorta and the pulmonary trunk, whilst the large veins and the main parts of the atria are situated on the right.

Grooves on the surface represent the divisions of the internal structure of the heart. The right surface of the heart is marked by the subsinusoidal groove which extends from the coronary groove to the apex of the heart. The paraconal groove runs over the left surface of the heart from the coronary groove to the distal end of the cranial margin. The fat-filled coronary groove contains the coronary blood vessels and marks the separation of the atria and ventricles.

===Pericardium===

The pericardium is the membrane that surrounds and protects the heart. It is composed of two layers separated by a narrow cavity. The inner layer is firmly attached to the heart wall and is known as the visceral layer or epicardium. The outer layer is composed of relatively inelastic connective tissue and is termed the parietal layer. This fibrous layer prevents distension of the heart, thus preventing excessive stretching of the heart muscle fibres. The cavity between the two layers contains a small volume of fluid which serves as a lubricant, facilitating the movement of the heart by minimising friction. The sternopericardiac ligament connects the parietal layer to the sternum and the phrenopericardiac ligament joins the parietal layer to the diaphragm. The latter is present only in canine and swine.

===Layers of the Heart Wall===

The wall of the heart consists of three layers: the epicardium (external layer), the myocardium (middle layer) and the endocardium (inner layer). The epicardium is the thin, transparent outer layer of the wall and is composed of delicate connective tissue. The myocardium, comprised of cardiac muscle tissue, makes up the majority of the cardiac wall and is responsible for its pumping action. The thickness of the myocardium mirrors the load to which each specific region of the heart is subjected. The endocardium is a thin layer of endothelium overlying a thin layer of connective tissue. It provides a smooth lining for the chambers of the heart and covers the valves. The endocardium is continuous with the endothelial lining of the large blood vessels attached to the heart.

====Structure of Cardiac Muscle====

Cardiac muscle fibres are shorter in length and larger in diameter than skeletal muscle fibres. They also exhibit branching, which gives an individual fibre a Y-shaped appearance. A typical cardiac muscle fibre is 50-100μm long and has a diameter of about 14μm. Normally, there is only one centrally located nucleus, although occasionally a cell may have two nuclei. The sarcoplasm of cardiac muscle is more abundant than that of skeletal muscle and the mitochondria are larger and more numerous. Cardiac muscle fibres have actin and myosin filaments arranged in the same way as skeletal muscle fibres and possess a well-developed T-tubule system. In contrast to [[Muscles - Anatomy & Physiology#Skeletal Muscle|skeletal muscle]], cardiac muscle does not fatigue, cannot be repaired when damaged and is regulated by the autonomic nervous system.

Although cardiac muscle fibres branch and interconnect with each other, they form two separate functional syncytia, one for the atria and another for the ventricles. The ends of each fibre in a network connect to its neighbours by irregular transverse thickenings of the sarcolemma called intercalated discs. The discs contain desmosomes, which hold the fibres together, and gap junctions, which allow ions to travel between cells and permit the rapid propagation of action potentials. Consequently, excitement of a single fibre of either network results in stimulation of all the other fibres in the network. As a result, each network contracts as a functional unit.

====Fibrous Skeleton====

In addition to cardiac muscle tissue, the heart wall also contains dense connective tissue that forms the fibrous skeleton of the heart. The fibrous skeleton is composed of dense connective tissue rings that surround the four heart orifices. The skeleton contains fibrocartilage in which nodules of bones (ossa cordis) may develop in some species. Although these bones occur most commonly in cattle, they are not restricted to this species. The skeleton performs several functions:

* It serves as a point of attachment for the heart valves
* The cardiac muscle bundles insert onto the fibrous skeleton.
* It prevents the valves from overstretching as blood passes through them.
* It acts as an electrical insulator thereby preventing the direct spread of action potentials from the atria to the ventricles.

===Chambers of the Heart===

The heart contains four chambers. The two upper chambers are the atria and the two lower chambers are the ventricles. On the cranial surface of each atrium is a pouch-like appendage called an auricle which is thought to increase the capacity of the atrium slightly.

The thickness of the myocardium of the four chambers varies according to function. The atria are thin-walled because they deliver blood into the adjacent ventricles and the ventricles are equipped with thick muscular walls because they pump blood over greater distances. Even though the right and left ventricles act as two separate pumps that simultaneously eject equal volumes of blood, the right side has a much smaller workload. This is because the right ventricle only pumps blood into the lungs, which are close by and present little resistance to blood flow. On the other hand, the left ventricle pumps blood to the rest of the body, where the resistance to blood flow is considerably higher. Consequently, the left ventricle works harder than the right ventricle to maintain the same blood flow rate. This difference in workload affects the anatomy of the ventricular walls; the muscular wall of the left ventricle being significantly thicker than that of the right.

====Right Atrium====

The right atrium forms the dorsocranial section of the base of the heart and receives blood from the cranial vena cava, caudal vena cava and coronary sinus. The interatrial septum is a thin partition dividing the right and left atria and possesses a characteristic oval depression called the fossa ovalis which is a remnant of the foetal foramen ovalis. The right atrium also houses the sinoatrial node. Blood flows from the right atrium to the right ventricle through the tricuspid valve (also know as the right atrioventricular valve).
In rabbits the right atrioventricular valve is bicuspid not tricuspid.

====Right Ventricle====

The right ventricle forms most of the anterior surface of the heart and is crescent-shaped in cross-section. The cusps of the tricuspid valve are connected to tendon-like cords, the chordae tendinae, which, in turn, are connected to cone-shaped papillary muscles within the ventricular wall. The right ventricle is separated from the left by a partition called the interventricular septum. The trabecula septomarginalis is a muscular band that traverses the lumen of the right ventricle. Deoxygenated blood passes from the right ventricle through the pulmonary semi-lunar valve to the pulmonary trunk, which conveys the blood to the lungs.

====Left Atrium====

The left atrium forms the dorsocaudal section of the base of the heart and is similar to the right atrium in structure and shape. It receives oxygenated blood from the lungs via the pulmonary veins. Blood passes from the left atrium to the left ventricle through the bicuspid or left atrioventricular valve. The left atrium lies under the tracheal bifurcation and enlargement of this area of the heart can cause breathing difficulties.

====Left Ventricle====

The left ventricle forms the apex of the heart and is conical in shape. Blood passes from the left ventricle to the ascending aorta through the aortic semi-lunar valve. From here some of the blood flows into the coronary arteries, which branch from the ascending aorta and carry blood to the heart wall. The remainder of the blood travels throughout the body.
<br>
{{Template:Learning
|dragster = [[Canine Heart Dissection Anatomy Resources (I & II)]]<br>[[Canine Heart Dissection Anatomy Resources (III & IV)]]<br>[[Cardiovascular System Histology Resource (I)]]
|videos = [[Video: Heart potcast|Heart potcast]]<br>[[Video: Heart (internal structure) potcast|Heart (internal structure) potcast]]<br>[[Video: Dorsal view of the ventricles and valves of the heart|Dorsal view of the ventricles and valves of the heart]]
|OVAM = [http://www.real3danatomy.com/thorax/dog-heart-lungs-ribs-3d.html Canine thoracic organs in Real 3D Anatomy, showing the heart, lungs and ribs and allowing detailed and accurate visualisation of organs "in-situ"]<br>[http://www.bristol.ac.uk/anatomy/media/elearning/internet/gracie/thorax/index.html Cross-sectional anatomy atlas of the canine thorax consisting of transverse sections and MRI images]<br>[http://www.um.es/anatvet/interactividad/ingles/avispi/practicas/practica3.htm Dissection plans of the thoracic cavity and heart]<br>[http://www.onlineveterinaryanatomy.net/sites/default/files/original_media/document/asset_8875_CDV.C.1_coronary_arteries_all.pdf Canine Heart - Coronary Artery Cast]<br>[http://www.onlineveterinaryanatomy.net/sites/default/files/original_media/document/asset_8864_cdv.c.18_all.pdf Plastinated Canine Heart (various views)]<br>[http://www.onlineveterinaryanatomy.net/content/cow-heart-internal-cast Internal Cast of Bovine Heart]<br>[http://www.onlineveterinaryanatomy.net/content/bronchial-and-heart-cast Canine Heart and Bronchial Cast]
|Vetstream = [https://www.vetstream.com/canis/Content/Disease/dis60195.asp Heart Failure]
}}

{{Chapter}}
{{Mansonchapter
|chapterlink = http://www.mansonpublishing.co.uk/book-images/9781840761535_sample.pdf
|chaptername = Normal Cardiovascular System
|book = Cardiovascular Disease in Small Animal Medicine
|author = Wendy A. Ware
|isbn = 9781840761535
}}

== Webinars ==
<rss max="10" highlight="heart cardiac cardiology">https://www.thewebinarvet.com/cardiology/webinars/feed</rss>

[[Category:Heart - Anatomy & Physiology]]
[[Category:Cardiology Section]]

Heart Structure - Anatomy & Physiology

2022-10-27T19:26:23Z

Roytwv:

{{OpenPagesTop}}
==Structure of the Heart==
[[Image:Aspinall Slide7.JPG|thumb|right|350px|<small>Image from [http://www.elsevierhealth.co.uk/veterinary-nursing/spe-60136/ Aspinall, The Complete Textbook of Veterinary Nursing], Elsevier Health Sciences, ''All rights reserved''</small>]]
[[Image:Aspinall Slide8.JPG|thumb|right|350px|<small>Image from [http://www.elsevierhealth.co.uk/veterinary-nursing/spe-60136/ Aspinall, The Complete Textbook of Veterinary Nursing], Elsevier Health Sciences, ''All rights reserved''</small>]]
===Position and Shape of the Heart===

The heart is located in the thoracic cavity in between the [[Lungs - Anatomy & Physiology|lungs]], 60% of it lying to the left of the median plane. The heart’s lateral projection extends from [[Ribs and Sternum - Anatomy & Physiology|rib]] 3 to 6. Most of the heart’s surface is covered by the [[Lungs - Anatomy & Physiology|lungs]] and in juveniles it is bordered cranially by the [[Thymus - Anatomy & Physiology|thymus]]. Caudally the heart extends as far as the [[Diaphragm - Anatomy & Physiology|diaphragm]]. Variations in position and size exist among individuals depending on species, breed, age, fitness and pathology. Roughly speaking, the heart is responsible for about 0.75% of the bodyweight.

The heart is cone-shaped, with a broad base at the top from which the large blood vessels enter and exit. The tip, known as the apex, points downwards and lies close to the [[Ribs and Sternum - Anatomy & Physiology|sternum]]. The longitudinal axis of the heart is tilted to varying degrees depending on the species resulting in the base facing craniodorsally and the apex caudoventrally.

The heart has a right and left lateral surface, which meet cranially at the right ventricular border and caudally at the left ventricular border. The auricles of the atria are visible on the left side, surrounding the root of the aorta and the pulmonary trunk, whilst the large veins and the main parts of the atria are situated on the right.

Grooves on the surface represent the divisions of the internal structure of the heart. The right surface of the heart is marked by the subsinusoidal groove which extends from the coronary groove to the apex of the heart. The paraconal groove runs over the left surface of the heart from the coronary groove to the distal end of the cranial margin. The fat-filled coronary groove contains the coronary blood vessels and marks the separation of the atria and ventricles.

===Pericardium===

The pericardium is the membrane that surrounds and protects the heart. It is composed of two layers separated by a narrow cavity. The inner layer is firmly attached to the heart wall and is known as the visceral layer or epicardium. The outer layer is composed of relatively inelastic connective tissue and is termed the parietal layer. This fibrous layer prevents distension of the heart, thus preventing excessive stretching of the heart muscle fibres. The cavity between the two layers contains a small volume of fluid which serves as a lubricant, facilitating the movement of the heart by minimising friction. The sternopericardiac ligament connects the parietal layer to the sternum and the phrenopericardiac ligament joins the parietal layer to the diaphragm. The latter is present only in canine and swine.

===Layers of the Heart Wall===

The wall of the heart consists of three layers: the epicardium (external layer), the myocardium (middle layer) and the endocardium (inner layer). The epicardium is the thin, transparent outer layer of the wall and is composed of delicate connective tissue. The myocardium, comprised of cardiac muscle tissue, makes up the majority of the cardiac wall and is responsible for its pumping action. The thickness of the myocardium mirrors the load to which each specific region of the heart is subjected. The endocardium is a thin layer of endothelium overlying a thin layer of connective tissue. It provides a smooth lining for the chambers of the heart and covers the valves. The endocardium is continuous with the endothelial lining of the large blood vessels attached to the heart.

====Structure of Cardiac Muscle====

Cardiac muscle fibres are shorter in length and larger in diameter than skeletal muscle fibres. They also exhibit branching, which gives an individual fibre a Y-shaped appearance. A typical cardiac muscle fibre is 50-100μm long and has a diameter of about 14μm. Normally, there is only one centrally located nucleus, although occasionally a cell may have two nuclei. The sarcoplasm of cardiac muscle is more abundant than that of skeletal muscle and the mitochondria are larger and more numerous. Cardiac muscle fibres have actin and myosin filaments arranged in the same way as skeletal muscle fibres and possess a well-developed T-tubule system. In contrast to [[Muscles - Anatomy & Physiology#Skeletal Muscle|skeletal muscle]], cardiac muscle does not fatigue, cannot be repaired when damaged and is regulated by the autonomic nervous system.

Although cardiac muscle fibres branch and interconnect with each other, they form two separate functional syncytia, one for the atria and another for the ventricles. The ends of each fibre in a network connect to its neighbours by irregular transverse thickenings of the sarcolemma called intercalated discs. The discs contain desmosomes, which hold the fibres together, and gap junctions, which allow ions to travel between cells and permit the rapid propagation of action potentials. Consequently, excitement of a single fibre of either network results in stimulation of all the other fibres in the network. As a result, each network contracts as a functional unit.

====Fibrous Skeleton====

In addition to cardiac muscle tissue, the heart wall also contains dense connective tissue that forms the fibrous skeleton of the heart. The fibrous skeleton is composed of dense connective tissue rings that surround the four heart orifices. The skeleton contains fibrocartilage in which nodules of bones (ossa cordis) may develop in some species. Although these bones occur most commonly in cattle, they are not restricted to this species. The skeleton performs several functions:

* It serves as a point of attachment for the heart valves
* The cardiac muscle bundles insert onto the fibrous skeleton.
* It prevents the valves from overstretching as blood passes through them.
* It acts as an electrical insulator thereby preventing the direct spread of action potentials from the atria to the ventricles.

===Chambers of the Heart===

The heart contains four chambers. The two upper chambers are the atria and the two lower chambers are the ventricles. On the cranial surface of each atrium is a pouch-like appendage called an auricle which is thought to increase the capacity of the atrium slightly.

The thickness of the myocardium of the four chambers varies according to function. The atria are thin-walled because they deliver blood into the adjacent ventricles and the ventricles are equipped with thick muscular walls because they pump blood over greater distances. Even though the right and left ventricles act as two separate pumps that simultaneously eject equal volumes of blood, the right side has a much smaller workload. This is because the right ventricle only pumps blood into the lungs, which are close by and present little resistance to blood flow. On the other hand, the left ventricle pumps blood to the rest of the body, where the resistance to blood flow is considerably higher. Consequently, the left ventricle works harder than the right ventricle to maintain the same blood flow rate. This difference in workload affects the anatomy of the ventricular walls; the muscular wall of the left ventricle being significantly thicker than that of the right.

====Right Atrium====

The right atrium forms the dorsocranial section of the base of the heart and receives blood from the cranial vena cava, caudal vena cava and coronary sinus. The interatrial septum is a thin partition dividing the right and left atria and possesses a characteristic oval depression called the fossa ovalis which is a remnant of the foetal foramen ovalis. The right atrium also houses the sinoatrial node. Blood flows from the right atrium to the right ventricle through the tricuspid valve (also know as the right atrioventricular valve).
In rabbits the right atrioventricular valve is bicuspid not tricuspid.

====Right Ventricle====

The right ventricle forms most of the anterior surface of the heart and is crescent-shaped in cross-section. The cusps of the tricuspid valve are connected to tendon-like cords, the chordae tendinae, which, in turn, are connected to cone-shaped papillary muscles within the ventricular wall. The right ventricle is separated from the left by a partition called the interventricular septum. The trabecula septomarginalis is a muscular band that traverses the lumen of the right ventricle. Deoxygenated blood passes from the right ventricle through the pulmonary semi-lunar valve to the pulmonary trunk, which conveys the blood to the lungs.

====Left Atrium====

The left atrium forms the dorsocaudal section of the base of the heart and is similar to the right atrium in structure and shape. It receives oxygenated blood from the lungs via the pulmonary veins. Blood passes from the left atrium to the left ventricle through the bicuspid or left atrioventricular valve. The left atrium lies under the tracheal bifurcation and enlargement of this area of the heart can cause breathing difficulties.

====Left Ventricle====

The left ventricle forms the apex of the heart and is conical in shape. Blood passes from the left ventricle to the ascending aorta through the aortic semi-lunar valve. From here some of the blood flows into the coronary arteries, which branch from the ascending aorta and carry blood to the heart wall. The remainder of the blood travels throughout the body.
<br>
{{Template:Learning
|dragster = [[Canine Heart Dissection Anatomy Resources (I & II)]]<br>[[Canine Heart Dissection Anatomy Resources (III & IV)]]<br>[[Cardiovascular System Histology Resource (I)]]
|videos = [[Video: Heart potcast|Heart potcast]]<br>[[Video: Heart (internal structure) potcast|Heart (internal structure) potcast]]<br>[[Video: Dorsal view of the ventricles and valves of the heart|Dorsal view of the ventricles and valves of the heart]]
|OVAM = [http://www.real3danatomy.com/thorax/dog-heart-lungs-ribs-3d.html Canine thoracic organs in Real 3D Anatomy, showing the heart, lungs and ribs and allowing detailed and accurate visualisation of organs "in-situ"]<br>[http://www.bristol.ac.uk/anatomy/media/elearning/internet/gracie/thorax/index.html Cross-sectional anatomy atlas of the canine thorax consisting of transverse sections and MRI images]<br>[http://www.um.es/anatvet/interactividad/ingles/avispi/practicas/practica3.htm Dissection plans of the thoracic cavity and heart]<br>[http://www.onlineveterinaryanatomy.net/sites/default/files/original_media/document/asset_8875_CDV.C.1_coronary_arteries_all.pdf Canine Heart - Coronary Artery Cast]<br>[http://www.onlineveterinaryanatomy.net/sites/default/files/original_media/document/asset_8864_cdv.c.18_all.pdf Plastinated Canine Heart (various views)]<br>[http://www.onlineveterinaryanatomy.net/content/cow-heart-internal-cast Internal Cast of Bovine Heart]<br>[http://www.onlineveterinaryanatomy.net/content/bronchial-and-heart-cast Canine Heart and Bronchial Cast]
|Vetstream = [https://www.vetstream.com/canis/Content/Disease/dis60195.asp Heart Failure]
}}

{{Chapter}}
{{Mansonchapter
|chapterlink = http://www.mansonpublishing.co.uk/book-images/9781840761535_sample.pdf
|chaptername = Normal Cardiovascular System
|book = Cardiovascular Disease in Small Animal Medicine
|author = Wendy A. Ware
|isbn = 9781840761535
}}

== Webinars ==
<rss max="10" highlight="none">https://www.thewebinarvet.com/urogenital-and-reproduction/webinars/feed</rss>
'''[https://www.thewebinarvet.com/webinar/every-last-drop-squeezing-the-most-from-your-diuretics?utm_source=wikivet&utm_medium=link&utm_campaign=Heart_Structure Every last drop: squeezing the most from your diuretics]'''

'''[https://www.thewebinarvet.com/webinar/diagnosing-heart-failure-in-general-practice?utm_source=wikivet&utm_medium=link&utm_campaign=Heart_Structure Diagnosing Heart Failure in General Practice]'''

'''[https://www.thewebinarvet.com/webinar/management-of-congestive-heart-failure-in-dogs-and-cats?utm_source=wikivet&utm_medium=link&utm_campaign=Heart_Structure Management of congestive heart failure in dogs and cats]'''

'''[https://www.thewebinarvet.com/webinar/heart-murmurs-when-should-i-investigate?utm_source=wikivet&utm_medium=link&utm_campaign=Heart_Structure Heart murmurs: when should I investigate?]'''

'''[https://www.thewebinarvet.com/webinar/heart-disease-in-small-mammals?utm_source=wikivet&utm_medium=link&utm_campaign=Heart_Structure Heart disease in small mammals]'''

'''[https://www.thewebinarvet.com/webinar/feline-cardiology?utm_source=wikivet&utm_medium=link&utm_campaign=Heart_Structure Treatment of feline cardiomyopathy: establishing the what, when and how?]'''

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[[Category:Heart - Anatomy & Physiology]]
[[Category:Cardiology Section]]

Hindlimb - Anatomy & Physiology

2022-10-27T19:25:23Z

Roytwv:

{{OpenPagesTop}}
==Common structures of the Proximal Hindlimb and Pelvis==

===Ilium===

The ilium makes up the craniodorsal part of the hip bone. It extends in a cranio-dorsal direction, from the hip joint to the articulation with the sacrum. It is made from a cranial wing and a caudal body.

'''''Ilial Wing'''''

The margin of the wing is known as the '''iliac crest'''. Along the crest are two very important anatomical landmarks:
:#'''Tuber Coxae''' or Coxal Tuberosity forms the palpable point of the hip.
:#'''Sacral Tuber''' is the thickened mediodorsal angle of the ilial wing.

The '''lateral''' surface of the wing provides a point of attachment for the gluteal muscles. The '''medial''' surface has two distinct parts:
:# The lateroventral part provides the point of insertion for many pelvic muscles.
:# The mediodorsal part articulates with the '''sacrum''' forming the '''sacroiliac joint'''.

The caudodorsal border of the wing is very concave and along its surface is the '''greater sciatic notch'''. This is where the '''sciatic nerve''' runs over the ilium.

'''''Ilial Body'''''

The only anatomical feature of note is the '''psoas tubercle''' on the ventral border. This provides attachment for the psoas muscle.

Click here for [[Ossification Hindlimb - Anatomy & Physiology#Ilium|Ossification centers of the ilium]].

===Ischium===

The Ischium can be divided into three main sections:
:#The '''body''' is part of the acetabulum. The dorsal border is continuous with that of the ilium forming the '''ischiatic spine''' which tapers towards the lesser sciatic notch.
:#The '''caudal plate''' extends cranially into the symphysial and acetabular branches, which form the caudal borders of the '''obturator foramen'''. The caudal section is thickened creating the '''ischial tuberosity''' that is a visible landmark in most animals. The medial caudal borders meet in a concave fashion forming a broad and deep notch called the '''ischial arch'''.
:#The '''medial branch''' forms the caudal section of the pelvic symphysis.

Click here for [[Ossification Hindlimb - Anatomy & Physiology#Ischium|ossification centers of the ischium]].

===Pubis===

The pubis is an L shaped bone that makes up one of the three bones of the pelvis. It consists of three parts:

#'''Body'''
#Transerse '''acetabular branch''' the cranial edge of which is the '''pectin of pubis''' and forms the '''iliopubic emminence''', to which some of the abdominal muscles attach.
#Sagittal '''symphysial branch'''

The two pubis fuse at the cranial section of the '''pubic symphysis'''. Lying off the ventral surface of the symphysis is the '''ventral pubic tubercle'''. The pubis forms more than half the '''obturator foramen'''. This is an opening in the pelvic floor that allows the obturator nerve to pass through it. The foramen is closed by musculature and soft tissue.

Click here for the [[Ossification Hindlimb - Anatomy & Physiology#Pubis|ossification centers of the pubis]].

===Femur===

The femur is the strongest of the long bones and provides the origin and attachment for many muscles and tendons. This means that it is characteristically modelled for each species. Despite this it can be divided into three basic parts:

1. '''''The Femoral Head'''''
:The head is offset from the main shaft of the femur, points in a medial direction and articulates with the acetabulum. It has a hemispherical articular surface with an associated '''notch''', ''fovea capitis'', which provides attachment for the '''intracapsular ligament'''. Lateral to the head is the '''greater trochanter'''. This process provides attachment to the gluteal muscles. The '''trochantic fossa''' separates the greater trochanter and the neck of the femur. It provides a site of insertion for the deep hip muscles. The '''lesser trochanter''' is a smaller process on the medial side that provides a site of attachment for the iliopsoas.

2. '''''Femoral Shaft'''''
:The caudal surface is roughened proximally and is framed by the '''medial and lateral lips'''. These lips extend distally and enclose the '''popliteal surface'''. They also provide attachment for the adductor muscles.

3. '''''Distal Extremity'''''
:This consists of the '''medial and lateral condyles''' caudally and a trochlea cranially. The condyles articulate with the tibia and menisci to form the '''femorotibial joint'''. The '''intercondylar fossa''' lies between the condyles and is separated from the popliteal surface by the '''intercondylar line'''. Both condyles are roughened on their abaxial surfaces, providing attachment for the collateral ligaments of the stifle joint. The '''extensor fossa''' is one of a pair of depressions on the lateral condyle. It is the more cranial of the two and forms an attachment point for the long digital extensor and third perineal muscle. The caudal depression gives origin to the popliteal muscle. On the caudal aspect of each condyle are facets for the articulation with the '''fabellae'''. These are sesamoid bones that are embedded in the tendinous insertion of the '''gastrocnemius'''. The '''trochlea''' is made up of two ridges and a groove that articulates with the '''patella''' to form the '''femoropatellar joint'''.

Click here for the [[Ossification Hindlimb - Anatomy & Physiology#Femur|ossification centers of the femur]].

==Joints of the Proximal Hindlimb==

===Sacroiliac Joint===

This is a '''synovial joint''' that is formed by the articulations between the auricular surfaces of the ilial wing and the sacrum. It has a joint capsule that tightly surrounds the joint and is strengthened by the '''ventral sacroiliac ligaments'''. The sacroiliac ligaments are:

#'''Interosseous sacroiliac ligaments''' - these lie between the iliac tuberosity and the dorsal aspect of the sacral wing.
#'''Dorsal Sacroiliac ligaments''' - this is made up of two branches. The short branch connects the sacral tuber to either the mammilary processes (carnivores and pigs)or to the spinous processes (ruminants and horses) of the sacrum. The long branch connects the sacral tuber to the lateral aspect of the sacrum.
#The '''sacrotuberous ligament''' - is highly variable among species.

{{Template:Learning
|videos = [[Video: Sacro-tuberous (sacro-sciatic) ligament dissection|Sacro-tuberous (sacro-sciatic) ligament dissection]]
}}

===Coxofemoral/Hip Joint===

This is a spheroidal joint formed by the femoral head and the '''acetabulum'''. The '''acetabulum''' is formed by all three pelvic bones and an additional '''small acetabular bone''' in carnivores. The craniolateral part is made by the ilium, the caudolateral part by the ischium and the medial part by the pubis. The cavity of the acetabulum consists of a peripheral '''articular lunate surface''' and the non-articular '''acetabular fossa''' in its centre. The lunate surface is crescent shaped and has on its medial aspect the '''acetabular notch'''. Cattle also have a '''cranioventral notch ''' present. The '''acetabular lip''' is a band of fibrocartilage that lies on the acetabular rim, thus deepening the acetabulum. The joint capsule is large and attaches to the acetabular lip.

The '''ligament of the femoral head''' connects the fovea in the head, by running through the acetabular notch, to the acetabular fossa. It is covered by a synovial membrane and for the majority is intracapsular. The '''acessory ligament of the femur''' is only present in the horse. It originates from the straight muscle of the abdomen and passes through the acetabular notch to finally attach in the fovea of the femoral head. The '''transverse acetabular ligament''' crosses the acetabular notch and ensures that the other two ligaments remain in their notch.

==Common Structures of the Distal Hindlimb==

===Tibia===

The tibia is one of the major weight bearing bones of the hind limb and is involved in both the stifle and hock. The tibia can be divided into three distinct sections:

1.'''''Proximal Extremity'''''
:It is three sided and has two condyles which are separated by the '''popliteal notch''' on its caudal aspect. The condyles have an articular surface which articulates with its corresponding femoral condyle or the distal surface of the meniscus. In between these articular surfaces lies the '''intercondylar eminence'''. The '''central intercondylar area''' divides this into a '''higher medial part''' and a '''lower lateral part'''. Cranial and caudal to the eminence are depressions where ligaments attach. The lateral side of the condyle has an articular facet for the articulation with the fibula. The '''extensor groove''' is a large notch on the craniolateral aspect which allows passage of the long digital extensor muscle.

2.'''''Tibial Shaft'''''
:It is craniocaudally compressed. The '''tibial tuberosity/tibial crest''' projects cranially from the proximal part of the shaft and is an important palpable landmark. The '''cranial border of the tibia''' is an extension of the crest distally. It divides the cranial aspect of the shaft in two. The medial aspect is subcutaneous and the lateral aspect is covered in muscles.

3. '''''Distal Extremity'''''
:This carries the '''cochlea''' which has two grooves divided by a ridge. This central ridge is directed sagittally in most species. The cochlea articulates with the trochlear ridges of the talus. The '''medial malleolus''' lies on the medial side of the cochlea and is a bony protuberence. The lateral aspect of the cochlea is highly variable in domestic species.

Click here for [[Ossification Hindlimb - Anatomy & Physiology#Tibia|ossification centers of the tibia]].

===Fibula===

The fibula lies laterally to the tibia and proximally doesn't interact with the stifle joint. The fibula consists of a '''proximal head''', a '''neck''', a '''shaft''' and a distal extremity/'''lateral malleoulus'''. During evolution, the fibula has been reduced in size and so also in relative strength and function. The amount of reduction is highly variable in domestic species.

===Tarsal bones===

The '''tarsus/hock''' is made up of two bones that lie between the crus and metatarsals. The proximal row is made of the '''talus''' and '''calcaneous''' and articulate with the tibia forming the '''tarsocrural joint'''. The distal row is made up of the central, 1st, 2nd, 3rd and 4th tarsal bones. The pattern of these bones is highly variable amongst domestic species, but in general they articulate with proximal row forming the '''tarsocrural joint''' and with the metatarsal bones forming the '''tarsometatarsal joint'''.

'''''Talus'''''
:The largest bone of the tarsus. It is the medial bone of the proximal row. It can be divided into three distinct areas; the compact '''body''', the '''trochlea''' and the '''head'''. The '''trochlea''' has prominent sagittal ridges dorsoproximally that articulate with the sagittal grooves and intermediate ridge of the distal end of the '''tibia'''. The cylindrical '''head''' is a smaller distal trochlea that articulates with the '''central tarsal bone'''. The plantar and lateral sides articulate with the '''calcaneous'''.

'''''Calcaneus'''''
:It lies laterally and plantar to the '''talus'''. It articulates medially and dorsally to the talus and distally towards the 4th tarsal bone. It has a proximal plantar projection called the '''calcaneal tuberosity''', it is this that forms the palpable '''point of the hock'''. It acts as a lever for muscles involved in hock extension. The '''susentaculum tali''' lies on the medial aspect of the distal portion of the calcaneus. It supports the deep digital flexor tendon and overlaps the talus on its plantar side.

'''''Distal Row of Tarsal Bones'''''
:These are highly variable amongst species but are discussed on their relevant pages.

==Joints of the Distal Hindlimb==

===Stifle Joint===

[[Image:stifle anatomy.jpg|thumb|right|250px|The Stifle, Cranial Caudal View - Copyright RVC]]

A composite, incongruent hinge joint made up of the '''femorotibial joint''' and '''femoropatellar joint'''.

'''''Femorotibial Joint'''''
:Essentially, this joint is formed between the femoral condyles and the proximal end of the tibia. A '''meniscus''' exists between each condyle and the tibia to compensate for any incongruency of the articular surfaces. The meniscus is a semilunar, fibrocartilage with a thick, convex peripheral border and central thin, concave border. The surface facing the femoral condyles is concave and facing the tibia it is flattened. As a condylar joint, the principal movements are '''flexion''' and '''extension''', but due to the presence of the menisci there is a limited amount of rotation. The '''fibrous layer''' of the joint capsule attaches to the margins of the articular surfaces and menisci and so completely encircles the femoral condyles. The '''synovial layer''' of the capsule covers the cruciates and forms a partition between the medial and lateral parts of the joint. These sacs are further separated by the menisci into a proximal and distal communicating compartments. The lateral femorotibial joint contains two pouches; one ensheathes the origin of the tendinous origin of the popliteal and the other ensheathes the origin of the long digital extensor at the extensor fossa.

'''''Meniscal Ligaments'''''
:'''Cranial tibial ligaments of the menisci''' - connecting the cranial aspect of the menisci to the medial and lateral cranial intercondyloid area of the tibia.
:'''Caudal tibial ligaments of the menisci''' - the medial ligament connects the caudal angle of the medial meniscus to the caudal intercondyloid area of the tibia. The lateral ligament connects the caudal angle of the lateral meniscus to the popliteal notch of the tibia.
:'''Femoral ligament of the lateral meniscus''' - connects the caudal angle of the lateral meniscus to the inside aspect of the medial femoral condyle.
:'''Transverse ligament''' - connects the cranial angles of the lateral and medial menisci. Found in carnivores and cattle.

'''''Femorotibial ligaments'''''
:'''Lateral and Medial Collateral Ligaments''' - The lateral connects the lateral epicondyle of the femur to both the lateral condyle of the tibia and the head of the fibula. The medial connects the medial epicondyle of the femur to just distal to the margin of the medial condyle of the tibia. This ligament fuses with the joint capsule and medial meniscus.
:'''Cranial and Caudal Cruciate Ligaments''' - These ligaments sit in the intercondyloid fossa of the femur in between the two synovial sacs. The cranial connects the lateral femoral condyle to the central intercondylar area of the tibia. The caudal connects the medial femoral condyle to the popliteal notch of the tibia.
:'''Oblique Popliteal Ligament''' - This is made of fibrous strands that are embedded in the joint capsule and run in latero-proximal to medial-distal direction.

'''''Femoropatellar Joint'''''
:This joint is formed between the articular surfaces of the patella and femur. The ligaments of this joint can be grouped as the '''femoropatellar ligaments''' and the '''patellar ligament'''. Both these groups of ligaments are highly species specific and are discussed on the species pages.

===Patella===

This is the largest '''sesamoid bone''' and lies in the tendinous insertion of the quadriceps muscle. The articular surface is on the caudal aspect and faces the femur. The free surface, faces cranial and is palpable in all species. The base is at the proximal end and is rough due to muscular attachments. The apex is at the distal end.

===Tarsal Joint/Hock===

A '''composite joint''' between the tibia, fibula, tarsal bones and metatarsals which has four levels of articulation. The joint capsules' '''fibrous layer''', extends from the distal crus to the proximal metatarsal and thus covers the whole tarsus. The '''synovial layer''' forms four synovial sacs for each level of articulation. The points of articulations are: '''Tarsocrural Joint''', '''Proximal Intertarsal Joint''', '''Distal Intertarsal Joint''' and the '''Tarsometatarsal Joint'''. The intratarsal joints are very closely apposed and so allow very little movement.

'''''Tarsocrural Joint'''''
:A cochlear joint, formed by the articulation of the trochlea of the talus and the distal end of the tibia. It is also the articulation between the calcaneous and the distal end of the fibula or lateral malleolus in cows. It has a large joint capsule that communicates with the proximal intertarsal joint. It has two plantar pouches that extend proximally above the medial and lateral malleoli. It also has a dorsal pouch that continues under the medial tendon of the cranial tibial muscle.

'''''Proximal Intertarsal Joint'''''
:Proximally, the talus and calcaneus articulate, and distally the central and forth tarsal bone articulate. The extent of direction of movement is species variable. A rigid joint is formed by the central tarsal bone and the small tarsal bones distally.

'''''Tarsometatarsal Joint'''''
:This is the articulation between the distal tarsal bones and the metatarsal bones.

'''''Ligaments of the Tarsus'''''
:# '''Long lateral collateral ligament''' connects the lateral malleolus to the proximal part of the lateral metatarsal bones. Along its course it attaches to the lateral tarsal bones.
:# '''Short lateral collateral ligament''' connects the lateral malleoulus to the calcaneus and the talus, and lies deep to the long lateral collateral ligament.
:# '''Long medial collateral ligament''' connects the medial malleolus to the proximal part of the medial metatarsal bones. Along its course it attaches to the medial tarsal bones.
:# '''Short medial collateral ligament''' connects the medial malleolus to the calcaneus and the talus and is deep to the long ligament.
:# '''Dorsal tarsal ligament''' is a triangular sheath, which is spread between the medial part of the talus, the central and 3rd tarsal bones and the 3rd and 4th metatarsal bones.
:# '''Long plantar ligament''' is a strong ligament connecting the calcaneus to the central and 4th tarsal bones and the proximal part of the 3rd and 4th metatarsal bones.

Numerous short ligaments bridge the joint spaces in the intratarsal joints. Strong fascia help keep tendons in place and are partially fused to the joint capsule. The most important are the '''proximal extensor retinaculum''', which holds down the tendon of the long digital extensor and the cranial tibial muscles, and the '''distal extensor retinaculum''', which holds the tendon of the long digital extensor in place.

==Muscles of the Hindlimb==

===Girdle Musculature===

These muscles arise from the ventral aspect of the lumbar vertebrae and will insert on either the pelvis or femur. They are also known as the '''sublumbar muscles'''. Their main function is to stabilise the vertebral column and pelvis during locomotion and for control of dorsiflexion and ventriflexion of the spine.

'''Psoas Minor'''
:Function: flexion of the vertebral column during the stance phase. Stabilisation of the vertebral column.
:Origin: 2nd-3rd caudal thoracic vertebrae on their ventral aspect and the 4th/5th cranial lumbar vertebrae.
:Insertion: via a strong tendon to the psoas tubercle of the femoral shaft.

'''Iliopsoas'''
:The strongest muscle of the girdle.
:Function: Flexion of the hip and outward rotation of the stifle. ie. draws hindlimb forward.
:In all animals, except carnivores, where they are fused, the muscle can be divided into two distinct parts.

'''Greater Psoas''' - the lumbar portion.
:Origin: last thoracic vertebrae and ribs and the bodies and transverse processes of the lumbar vertebrae.
:Insertion: Incorporates with iliac muscle and inserts on the lesser trochanter.
:It is positioned dorsally to the psoas minor and ventral to the quadrate lumbar muscle.

'''Iliac '''muscle
:Origin: wing and shaft of ilium.
:Insertion: via the common iliopsoas tendon to the lesser trochanter of the femur.
:The muscle passes through the '''muscular lacuna'''; an opening between the os coxae laterally and caudally, the rectus abdominus medially and the iliac fascia cranially.

'''Quadrate Lumbar''' muscle
:Function: stabilisation of the lumbar vertebral column.
:Origin: Ventral aspect of the transverse processes of the lumbar vertebrae and the proximal ends of the ribs.
:Insertion: Ventral aspect of the wings of the ilium and sacrum.

===Rump Muscles===

The rump muscles main function is to extend the hip and some also extend the stifle and tarsus. They can be grouped into four distinct groups; the gluteals, the hamstrings, the medial muscles of the thigh and the inner pelvic muscles.

===='''The Gluteals'''====

They lie over the lateral and caudal aspect of the pelvic wall and extend between the thigh and ilium.

'''''Superficial Gluteal Muscle'''''
:This muscle shows great species variance and will be explained on their respective pages.
:Function - Extension of the hip, also retraction of the limb and supports outward rotation.

'''''Gluteofemoral Muscle'''''
:This muscle only exists in the cat.
:Function - Retraction and abduction of the limb and hip extension.
:Origin - 2nd-4th caudal vertebrae.
:Insertion - Lateral aspect of patella and fascia lata via an aponeurosis.
:Location - Between the superficial gluteal muscle and biceps muscle of the thigh.

'''''Middle Gluteal Muscle'''''
:This muscle also shows great species variance, though all species have a superficial and deep portion that are separated by a tendinous sheet. Both tendons on their site of insertion are protected by a synovial bursa.
:Function - most powerful extensor of the hip, also abducts and retracts the limb.

'''''Piriform Muscle'''''
:This is fused to the middle gluteal muscle except in carnivores.
:Function - Extensor of hip and abducter of the limb.
:Origin - last sacral vertebrae and sacrotuberous ligament.
:Insertion - just distal to the greater trochanter on the lateral aspect of the femur.
:Location - caudal and medial to the middle gluteal and is covered by the superficial gluteal.

'''Deep Gluteal Muscle'''
:Function - abduction of the limb.
:Origin - lateral aspect of the ilial shaft.
:Insertion - via a short tendon to the greater trochanter.

'''''Tensor Muscle of the Fascia Lata'''''
:This muscle shows great species variance.
:Function - flexion of the hip and extension of the stifle.

===='''The Hamstrings'''====

These muscles cover the caudal aspect of the thigh and are multi-articular. They originate near the ischium and extend to the tibia and have some tendinous components that will make up the '''common calcanean tendon'''.

'''''Biceps Muscle of the thigh'''''
:The largest and most lateral of the muscles, it is superficial and covered only by fascia and skin. It consists of cranial part, arising from the sacrum and sacrotuberous ligament and a small caudal part arising from the ischium. The muscle is composed of multiple parts and has different points of insertion in different species.
:Function - Extension and abduction of the limb. The cranial part extends the hip and stifle, though the caudal part extends the hip but flexes the stifle. It also causes tarsal extension.
:See species pages as is very species specific.

'''''Abductor muscle of the thigh'''''
:Only present in carnivores.
:Function - abduction of the limb.
:Origin - sacrotuberous ligament.
:Insertion - crural fascia.

'''''Semitendinous'''''
:Function - extends the hip, stifle and tarsus when the foot makes contact with the ground, therefore propulsing the animal. On a non-weightbearing leg it flexes the stifle and rotates the leg back and out.
:Origin - the ischial tuberosity ('''pelvic head''').
:Insertion - cranial margin of the tibia and a tendinous insertion on the calcaneal tuberosity.

'''''Semimembranous'''''
:The most medial of the hamstrings.
:Function - Extension of the hip and stifle in a weightbearing stance. On a non-weightbearing limb, it adducts and retracts the limb.
:Origin - can be from either just the pelvic head or from the pelvic head and '''vertebral head'''. This is dependent on species.
:Insertion - onto the medial condyle of the femur and the medial condyle of the tibia.

===='''Medial Muscles of the Thigh'''====

This muscle groups' main functions are to adduct the limb and to prevent unwanted abduction. They lie between the pelvic floor and the medial aspect of the femur.

'''''Sartorius'''''
:Function - flexion of the hip, advancement and abduction of the limb. It can also extend the hip via its attachments to the crural fascia and stifle fascia.
:Origin - Coxal tuberosity; ilial shaft or tendon of psoas minor.
:Insertion - Deep fascia of the leg.
:Location - superficially on the craniomedial border of the thigh as a strap like muscle.

'''''Gracilis'''''
:Function - adductor of the limb, extends the hip.
:Origin - from an aponeurosis of the pelvic symphysis, the insertional tendons of the straight muscle of the abdomen. A tendinous plate is formed between the two aponeurosi of the gracilis' on which the adductor muscles originate.
:Insertion - An aponeurotic insertion with the crural fascia that attaches to the tibial crest.
:Location - broad muscular sheet on the caudal aspect of the medial part of the thigh.

'''''Pectineal Muscle'''''
:Function - flexor of the hip, adductor and supinator of the limb.
:Origin - iliopubic eminence of pelvic floor.
:Insertion - medial border of the femur.
:Location - a fusiform muscle extending between the pecten of the pubis, the pelvic floor and the femur.

'''''Adductor Muscles'''''
:Function - adduction of the limb, can also retract the limb.
:Origin - the tendinous plate of the gracilis muscles.
:Insertion - medial aspect of the femur, fascia and ligaments of the medial aspect of the stifle.

===='''Inner Pelvic Muscles'''====

This set of muscles are a rather mixed group of small muscles lying close to the hip joint. They lie between the pelvis and trochantic fossa of the femur.

'''''Internal Obturator'''''
:Only exists in carnivores and horses.
:Function - extension of the hip and rotation of the femur laterally.
:Origin and insertion - are both dependent on species involved.

'''''External Obturator'''''
:Function - supinator of the femur and adductor of the limb.
:Origin - the ventral pelvic surface close to the obturator foramen.
:Insertion - trochantic fossa.

'''''Gemellus'''''
:Function - rotation of the limb laterally.
:Origin - ischiatic spine.
:Insertion - unites partially with the internal obturator and so inserts on the trochantic fossa.

'''''Quadrate Muscle'''''
:Function - extension of the hip and retraction of the limb.
:Origin - ventral aspect of ischium.
:Insertion - trochantic fossa.

'''''Articular muscle of the hip joint'''''
:Only in carnivores and horses.
:Function - causes tension of the joint capsule and thus helps prevent damage to the peri-articular structures.
:Origin - Hip joint capsule.

===Muscles of the Stifle===

Many of the muscles of the hip (see [[Hindlimb - Anatomy & Physiology#Girdle Musculature|girdle musculature]] and [[Hindlimb - Anatomy & Physiology#Rump Muscles|rump muscles]]) act on the stifle by inserting on structures involved with the stifle or are distal to it. There are only really two muscles that act solely on the stifle; the '''quadriceps''' and the '''popliteal'''.

'''''Quadriceps'''''
:This muscle forms the main muscle bulk on the cranial aspect of the thigh, but is covered by the tensor muscle of the fascia lata, the sartorius and the medial femoral fascia. The quadriceps are the main extensors of the stifle and the straight muscle also flexes the hip. The muscle consists of four parts that have separate points of origin but have a common single tendon, the '''patella tendon''' that inserts onto the patella and '''tibial tuberosity'''.

The four parts are:
:# '''Lateral Vastus''' - On the craniolateral side of the femur, originating from the lateral aspect of the proximal femur.
:# '''Medial Vastus''' - On the craniomedial side of the femur, originating from the medial aspect of the proxial femur.
:# '''Intermediate Vastus''' - On the cranial surface of the femur, it is totally covered by the other quadriceps muscles and is the weakest muscle of the quadriceps.
:# '''Straight muscle/Rectus femoris''' - Originates from the ilial shaft cranial to the acetabulum and runs down to the patella tendon between the two bellies of the lateral and medial vastus.

'''''Popliteal'''''
:Function - flexor of the stifle and pronator of the leg.
:Origin - a tendinous origin from the lateral condyle of the femur.
:Insertion - a broad tendon on the medial and caudal surface of the proximal tibia.
:Location - On the caudal aspect of the stifle and runs under the lateral collateral ligament before it inserts.

{{Template:Learning
|OVAM = [http://www.onlineveterinaryanatomy.net/content/muscle-flashcards-crus-quicktime Muscle flashcards - muscles of the canine hindlimb]<br>[http://www.onlineveterinaryanatomy.net/content/muscle-flashcards-hip-quicktime Muscle flashcards - muscles of the canine hip]
}}

==Vasculature of the Hindlimb==

'''[[Arteries of the Hindlimb - Anatomy & Physiology|Arteries of the Hindlimb]]'''

'''[[Veins of the Hindlimb - Anatomy & Physiology|Veins of the Hindlimb]]'''

'''[[Lymphatics of the Hindlimb - Anatomy & Physiology|Lymphatics of the Hindlimb]]'''

==Innervation of the Hindlimb==

The nerves that supply the hindlimb arise from the lumbosacral plexus, that lies on the medial wall of the pelvis. These nerves are:

'''Femoral Nerve'''
:Origin - cranial part of the lumbosacral plexus, L4 and L5. (Sometimes L3 and L6)
:Motor innervation - Quadriceps and iliopsoas muscle.
:Sensory innervation - the medial aspect of the limb.
:Route - through the iliopsoas.

'''Obturator Nerve'''
:Origin - middle part of the lumbosacral plexus, L5 and L6.
:Motor innervation - adductor muscles; external obturator, adductor and gracilis.
:Sensory innervation - none.
:Route - through the iliopsoas, medial to the ilial shaft and then through the obturator foramen.

'''Gluteal Nerves'''
:Origin - L6, L7 and S1.
:Motor innervation - gluteal muscles, tensor fascia lata, biceps femoris and semitendinosus.
:Sensory innervation - none.
:Route - direct to the gluteals

'''Sciatic Nerve'''
:Origin - L6, L7, S1 and S2.
:Motor innervation - biceps femoris, semintendinosus, semimembranosus.
:Sensory innervation - the nerve divides into the tibial and fibula nerves where cutaneous fibres run.
:Route - the largest nerve in the body. It leaves the pelvis at the greater sciatic notch and curves in a ventral caudal direction around the hip joint. It runs distocaudally over the femur, between the biceps femoris medially and the adductor, semimembranosus and semitendinosus muscles medially. It then divides into the tibial and fibular nerves.

'''Tibial Nerve'''
:Origin - the sciatic nerve.
:Motor innervation - extensors of the hock, flexors of the digits, popliteal muscle.
:Sensory innervation - caudal aspect of the limb below the stifle.
:Route - it runs caudal to the stifle joint into the muscle.

'''Fibular (Peroneal Nerve)'''
:Origin - the sciatic nerve.
:Motor innervation - flexors of the hock, extensors of the digits.
:Sensory innervation - cranial and lateral aspect of the limb.
:Route - caudal to the stifle.

==Species Specifics==

Click here for information on the [[Canine Hindlimb - Anatomy & Physiology|canine hindlimb]].

Click here for information on the [[Bovine Hindlimb - Anatomy & Physiology|bovine hindlimb]].

==Webinars==
<rss max="10" highlight="none">https://www.thewebinarvet.com/orthopaedics/webinars/feed</rss>
[[Category:Musculoskeletal System - Anatomy & Physiology]]
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Hindlimb - Anatomy & Physiology

2022-10-27T19:24:48Z

Roytwv:

{{OpenPagesTop}}
==Common structures of the Proximal Hindlimb and Pelvis==

===Ilium===

The ilium makes up the craniodorsal part of the hip bone. It extends in a cranio-dorsal direction, from the hip joint to the articulation with the sacrum. It is made from a cranial wing and a caudal body.

'''''Ilial Wing'''''

The margin of the wing is known as the '''iliac crest'''. Along the crest are two very important anatomical landmarks:
:#'''Tuber Coxae''' or Coxal Tuberosity forms the palpable point of the hip.
:#'''Sacral Tuber''' is the thickened mediodorsal angle of the ilial wing.

The '''lateral''' surface of the wing provides a point of attachment for the gluteal muscles. The '''medial''' surface has two distinct parts:
:# The lateroventral part provides the point of insertion for many pelvic muscles.
:# The mediodorsal part articulates with the '''sacrum''' forming the '''sacroiliac joint'''.

The caudodorsal border of the wing is very concave and along its surface is the '''greater sciatic notch'''. This is where the '''sciatic nerve''' runs over the ilium.

'''''Ilial Body'''''

The only anatomical feature of note is the '''psoas tubercle''' on the ventral border. This provides attachment for the psoas muscle.

Click here for [[Ossification Hindlimb - Anatomy & Physiology#Ilium|Ossification centers of the ilium]].

===Ischium===

The Ischium can be divided into three main sections:
:#The '''body''' is part of the acetabulum. The dorsal border is continuous with that of the ilium forming the '''ischiatic spine''' which tapers towards the lesser sciatic notch.
:#The '''caudal plate''' extends cranially into the symphysial and acetabular branches, which form the caudal borders of the '''obturator foramen'''. The caudal section is thickened creating the '''ischial tuberosity''' that is a visible landmark in most animals. The medial caudal borders meet in a concave fashion forming a broad and deep notch called the '''ischial arch'''.
:#The '''medial branch''' forms the caudal section of the pelvic symphysis.

Click here for [[Ossification Hindlimb - Anatomy & Physiology#Ischium|ossification centers of the ischium]].

===Pubis===

The pubis is an L shaped bone that makes up one of the three bones of the pelvis. It consists of three parts:

#'''Body'''
#Transerse '''acetabular branch''' the cranial edge of which is the '''pectin of pubis''' and forms the '''iliopubic emminence''', to which some of the abdominal muscles attach.
#Sagittal '''symphysial branch'''

The two pubis fuse at the cranial section of the '''pubic symphysis'''. Lying off the ventral surface of the symphysis is the '''ventral pubic tubercle'''. The pubis forms more than half the '''obturator foramen'''. This is an opening in the pelvic floor that allows the obturator nerve to pass through it. The foramen is closed by musculature and soft tissue.

Click here for the [[Ossification Hindlimb - Anatomy & Physiology#Pubis|ossification centers of the pubis]].

===Femur===

The femur is the strongest of the long bones and provides the origin and attachment for many muscles and tendons. This means that it is characteristically modelled for each species. Despite this it can be divided into three basic parts:

1. '''''The Femoral Head'''''
:The head is offset from the main shaft of the femur, points in a medial direction and articulates with the acetabulum. It has a hemispherical articular surface with an associated '''notch''', ''fovea capitis'', which provides attachment for the '''intracapsular ligament'''. Lateral to the head is the '''greater trochanter'''. This process provides attachment to the gluteal muscles. The '''trochantic fossa''' separates the greater trochanter and the neck of the femur. It provides a site of insertion for the deep hip muscles. The '''lesser trochanter''' is a smaller process on the medial side that provides a site of attachment for the iliopsoas.

2. '''''Femoral Shaft'''''
:The caudal surface is roughened proximally and is framed by the '''medial and lateral lips'''. These lips extend distally and enclose the '''popliteal surface'''. They also provide attachment for the adductor muscles.

3. '''''Distal Extremity'''''
:This consists of the '''medial and lateral condyles''' caudally and a trochlea cranially. The condyles articulate with the tibia and menisci to form the '''femorotibial joint'''. The '''intercondylar fossa''' lies between the condyles and is separated from the popliteal surface by the '''intercondylar line'''. Both condyles are roughened on their abaxial surfaces, providing attachment for the collateral ligaments of the stifle joint. The '''extensor fossa''' is one of a pair of depressions on the lateral condyle. It is the more cranial of the two and forms an attachment point for the long digital extensor and third perineal muscle. The caudal depression gives origin to the popliteal muscle. On the caudal aspect of each condyle are facets for the articulation with the '''fabellae'''. These are sesamoid bones that are embedded in the tendinous insertion of the '''gastrocnemius'''. The '''trochlea''' is made up of two ridges and a groove that articulates with the '''patella''' to form the '''femoropatellar joint'''.

Click here for the [[Ossification Hindlimb - Anatomy & Physiology#Femur|ossification centers of the femur]].

==Joints of the Proximal Hindlimb==

===Sacroiliac Joint===

This is a '''synovial joint''' that is formed by the articulations between the auricular surfaces of the ilial wing and the sacrum. It has a joint capsule that tightly surrounds the joint and is strengthened by the '''ventral sacroiliac ligaments'''. The sacroiliac ligaments are:

#'''Interosseous sacroiliac ligaments''' - these lie between the iliac tuberosity and the dorsal aspect of the sacral wing.
#'''Dorsal Sacroiliac ligaments''' - this is made up of two branches. The short branch connects the sacral tuber to either the mammilary processes (carnivores and pigs)or to the spinous processes (ruminants and horses) of the sacrum. The long branch connects the sacral tuber to the lateral aspect of the sacrum.
#The '''sacrotuberous ligament''' - is highly variable among species.

{{Template:Learning
|videos = [[Video: Sacro-tuberous (sacro-sciatic) ligament dissection|Sacro-tuberous (sacro-sciatic) ligament dissection]]
}}

===Coxofemoral/Hip Joint===

This is a spheroidal joint formed by the femoral head and the '''acetabulum'''. The '''acetabulum''' is formed by all three pelvic bones and an additional '''small acetabular bone''' in carnivores. The craniolateral part is made by the ilium, the caudolateral part by the ischium and the medial part by the pubis. The cavity of the acetabulum consists of a peripheral '''articular lunate surface''' and the non-articular '''acetabular fossa''' in its centre. The lunate surface is crescent shaped and has on its medial aspect the '''acetabular notch'''. Cattle also have a '''cranioventral notch ''' present. The '''acetabular lip''' is a band of fibrocartilage that lies on the acetabular rim, thus deepening the acetabulum. The joint capsule is large and attaches to the acetabular lip.

The '''ligament of the femoral head''' connects the fovea in the head, by running through the acetabular notch, to the acetabular fossa. It is covered by a synovial membrane and for the majority is intracapsular. The '''acessory ligament of the femur''' is only present in the horse. It originates from the straight muscle of the abdomen and passes through the acetabular notch to finally attach in the fovea of the femoral head. The '''transverse acetabular ligament''' crosses the acetabular notch and ensures that the other two ligaments remain in their notch.

==Common Structures of the Distal Hindlimb==

===Tibia===

The tibia is one of the major weight bearing bones of the hind limb and is involved in both the stifle and hock. The tibia can be divided into three distinct sections:

1.'''''Proximal Extremity'''''
:It is three sided and has two condyles which are separated by the '''popliteal notch''' on its caudal aspect. The condyles have an articular surface which articulates with its corresponding femoral condyle or the distal surface of the meniscus. In between these articular surfaces lies the '''intercondylar eminence'''. The '''central intercondylar area''' divides this into a '''higher medial part''' and a '''lower lateral part'''. Cranial and caudal to the eminence are depressions where ligaments attach. The lateral side of the condyle has an articular facet for the articulation with the fibula. The '''extensor groove''' is a large notch on the craniolateral aspect which allows passage of the long digital extensor muscle.

2.'''''Tibial Shaft'''''
:It is craniocaudally compressed. The '''tibial tuberosity/tibial crest''' projects cranially from the proximal part of the shaft and is an important palpable landmark. The '''cranial border of the tibia''' is an extension of the crest distally. It divides the cranial aspect of the shaft in two. The medial aspect is subcutaneous and the lateral aspect is covered in muscles.

3. '''''Distal Extremity'''''
:This carries the '''cochlea''' which has two grooves divided by a ridge. This central ridge is directed sagittally in most species. The cochlea articulates with the trochlear ridges of the talus. The '''medial malleolus''' lies on the medial side of the cochlea and is a bony protuberence. The lateral aspect of the cochlea is highly variable in domestic species.

Click here for [[Ossification Hindlimb - Anatomy & Physiology#Tibia|ossification centers of the tibia]].

===Fibula===

The fibula lies laterally to the tibia and proximally doesn't interact with the stifle joint. The fibula consists of a '''proximal head''', a '''neck''', a '''shaft''' and a distal extremity/'''lateral malleoulus'''. During evolution, the fibula has been reduced in size and so also in relative strength and function. The amount of reduction is highly variable in domestic species.

===Tarsal bones===

The '''tarsus/hock''' is made up of two bones that lie between the crus and metatarsals. The proximal row is made of the '''talus''' and '''calcaneous''' and articulate with the tibia forming the '''tarsocrural joint'''. The distal row is made up of the central, 1st, 2nd, 3rd and 4th tarsal bones. The pattern of these bones is highly variable amongst domestic species, but in general they articulate with proximal row forming the '''tarsocrural joint''' and with the metatarsal bones forming the '''tarsometatarsal joint'''.

'''''Talus'''''
:The largest bone of the tarsus. It is the medial bone of the proximal row. It can be divided into three distinct areas; the compact '''body''', the '''trochlea''' and the '''head'''. The '''trochlea''' has prominent sagittal ridges dorsoproximally that articulate with the sagittal grooves and intermediate ridge of the distal end of the '''tibia'''. The cylindrical '''head''' is a smaller distal trochlea that articulates with the '''central tarsal bone'''. The plantar and lateral sides articulate with the '''calcaneous'''.

'''''Calcaneus'''''
:It lies laterally and plantar to the '''talus'''. It articulates medially and dorsally to the talus and distally towards the 4th tarsal bone. It has a proximal plantar projection called the '''calcaneal tuberosity''', it is this that forms the palpable '''point of the hock'''. It acts as a lever for muscles involved in hock extension. The '''susentaculum tali''' lies on the medial aspect of the distal portion of the calcaneus. It supports the deep digital flexor tendon and overlaps the talus on its plantar side.

'''''Distal Row of Tarsal Bones'''''
:These are highly variable amongst species but are discussed on their relevant pages.

==Joints of the Distal Hindlimb==

===Stifle Joint===

[[Image:stifle anatomy.jpg|thumb|right|250px|The Stifle, Cranial Caudal View - Copyright RVC]]

A composite, incongruent hinge joint made up of the '''femorotibial joint''' and '''femoropatellar joint'''.

'''''Femorotibial Joint'''''
:Essentially, this joint is formed between the femoral condyles and the proximal end of the tibia. A '''meniscus''' exists between each condyle and the tibia to compensate for any incongruency of the articular surfaces. The meniscus is a semilunar, fibrocartilage with a thick, convex peripheral border and central thin, concave border. The surface facing the femoral condyles is concave and facing the tibia it is flattened. As a condylar joint, the principal movements are '''flexion''' and '''extension''', but due to the presence of the menisci there is a limited amount of rotation. The '''fibrous layer''' of the joint capsule attaches to the margins of the articular surfaces and menisci and so completely encircles the femoral condyles. The '''synovial layer''' of the capsule covers the cruciates and forms a partition between the medial and lateral parts of the joint. These sacs are further separated by the menisci into a proximal and distal communicating compartments. The lateral femorotibial joint contains two pouches; one ensheathes the origin of the tendinous origin of the popliteal and the other ensheathes the origin of the long digital extensor at the extensor fossa.

'''''Meniscal Ligaments'''''
:'''Cranial tibial ligaments of the menisci''' - connecting the cranial aspect of the menisci to the medial and lateral cranial intercondyloid area of the tibia.
:'''Caudal tibial ligaments of the menisci''' - the medial ligament connects the caudal angle of the medial meniscus to the caudal intercondyloid area of the tibia. The lateral ligament connects the caudal angle of the lateral meniscus to the popliteal notch of the tibia.
:'''Femoral ligament of the lateral meniscus''' - connects the caudal angle of the lateral meniscus to the inside aspect of the medial femoral condyle.
:'''Transverse ligament''' - connects the cranial angles of the lateral and medial menisci. Found in carnivores and cattle.

'''''Femorotibial ligaments'''''
:'''Lateral and Medial Collateral Ligaments''' - The lateral connects the lateral epicondyle of the femur to both the lateral condyle of the tibia and the head of the fibula. The medial connects the medial epicondyle of the femur to just distal to the margin of the medial condyle of the tibia. This ligament fuses with the joint capsule and medial meniscus.
:'''Cranial and Caudal Cruciate Ligaments''' - These ligaments sit in the intercondyloid fossa of the femur in between the two synovial sacs. The cranial connects the lateral femoral condyle to the central intercondylar area of the tibia. The caudal connects the medial femoral condyle to the popliteal notch of the tibia.
:'''Oblique Popliteal Ligament''' - This is made of fibrous strands that are embedded in the joint capsule and run in latero-proximal to medial-distal direction.

'''''Femoropatellar Joint'''''
:This joint is formed between the articular surfaces of the patella and femur. The ligaments of this joint can be grouped as the '''femoropatellar ligaments''' and the '''patellar ligament'''. Both these groups of ligaments are highly species specific and are discussed on the species pages.

===Patella===

This is the largest '''sesamoid bone''' and lies in the tendinous insertion of the quadriceps muscle. The articular surface is on the caudal aspect and faces the femur. The free surface, faces cranial and is palpable in all species. The base is at the proximal end and is rough due to muscular attachments. The apex is at the distal end.

===Tarsal Joint/Hock===

A '''composite joint''' between the tibia, fibula, tarsal bones and metatarsals which has four levels of articulation. The joint capsules' '''fibrous layer''', extends from the distal crus to the proximal metatarsal and thus covers the whole tarsus. The '''synovial layer''' forms four synovial sacs for each level of articulation. The points of articulations are: '''Tarsocrural Joint''', '''Proximal Intertarsal Joint''', '''Distal Intertarsal Joint''' and the '''Tarsometatarsal Joint'''. The intratarsal joints are very closely apposed and so allow very little movement.

'''''Tarsocrural Joint'''''
:A cochlear joint, formed by the articulation of the trochlea of the talus and the distal end of the tibia. It is also the articulation between the calcaneous and the distal end of the fibula or lateral malleolus in cows. It has a large joint capsule that communicates with the proximal intertarsal joint. It has two plantar pouches that extend proximally above the medial and lateral malleoli. It also has a dorsal pouch that continues under the medial tendon of the cranial tibial muscle.

'''''Proximal Intertarsal Joint'''''
:Proximally, the talus and calcaneus articulate, and distally the central and forth tarsal bone articulate. The extent of direction of movement is species variable. A rigid joint is formed by the central tarsal bone and the small tarsal bones distally.

'''''Tarsometatarsal Joint'''''
:This is the articulation between the distal tarsal bones and the metatarsal bones.

'''''Ligaments of the Tarsus'''''
:# '''Long lateral collateral ligament''' connects the lateral malleolus to the proximal part of the lateral metatarsal bones. Along its course it attaches to the lateral tarsal bones.
:# '''Short lateral collateral ligament''' connects the lateral malleoulus to the calcaneus and the talus, and lies deep to the long lateral collateral ligament.
:# '''Long medial collateral ligament''' connects the medial malleolus to the proximal part of the medial metatarsal bones. Along its course it attaches to the medial tarsal bones.
:# '''Short medial collateral ligament''' connects the medial malleolus to the calcaneus and the talus and is deep to the long ligament.
:# '''Dorsal tarsal ligament''' is a triangular sheath, which is spread between the medial part of the talus, the central and 3rd tarsal bones and the 3rd and 4th metatarsal bones.
:# '''Long plantar ligament''' is a strong ligament connecting the calcaneus to the central and 4th tarsal bones and the proximal part of the 3rd and 4th metatarsal bones.

Numerous short ligaments bridge the joint spaces in the intratarsal joints. Strong fascia help keep tendons in place and are partially fused to the joint capsule. The most important are the '''proximal extensor retinaculum''', which holds down the tendon of the long digital extensor and the cranial tibial muscles, and the '''distal extensor retinaculum''', which holds the tendon of the long digital extensor in place.

==Muscles of the Hindlimb==

===Girdle Musculature===

These muscles arise from the ventral aspect of the lumbar vertebrae and will insert on either the pelvis or femur. They are also known as the '''sublumbar muscles'''. Their main function is to stabilise the vertebral column and pelvis during locomotion and for control of dorsiflexion and ventriflexion of the spine.

'''Psoas Minor'''
:Function: flexion of the vertebral column during the stance phase. Stabilisation of the vertebral column.
:Origin: 2nd-3rd caudal thoracic vertebrae on their ventral aspect and the 4th/5th cranial lumbar vertebrae.
:Insertion: via a strong tendon to the psoas tubercle of the femoral shaft.

'''Iliopsoas'''
:The strongest muscle of the girdle.
:Function: Flexion of the hip and outward rotation of the stifle. ie. draws hindlimb forward.
:In all animals, except carnivores, where they are fused, the muscle can be divided into two distinct parts.

'''Greater Psoas''' - the lumbar portion.
:Origin: last thoracic vertebrae and ribs and the bodies and transverse processes of the lumbar vertebrae.
:Insertion: Incorporates with iliac muscle and inserts on the lesser trochanter.
:It is positioned dorsally to the psoas minor and ventral to the quadrate lumbar muscle.

'''Iliac '''muscle
:Origin: wing and shaft of ilium.
:Insertion: via the common iliopsoas tendon to the lesser trochanter of the femur.
:The muscle passes through the '''muscular lacuna'''; an opening between the os coxae laterally and caudally, the rectus abdominus medially and the iliac fascia cranially.

'''Quadrate Lumbar''' muscle
:Function: stabilisation of the lumbar vertebral column.
:Origin: Ventral aspect of the transverse processes of the lumbar vertebrae and the proximal ends of the ribs.
:Insertion: Ventral aspect of the wings of the ilium and sacrum.

===Rump Muscles===

The rump muscles main function is to extend the hip and some also extend the stifle and tarsus. They can be grouped into four distinct groups; the gluteals, the hamstrings, the medial muscles of the thigh and the inner pelvic muscles.

===='''The Gluteals'''====

They lie over the lateral and caudal aspect of the pelvic wall and extend between the thigh and ilium.

'''''Superficial Gluteal Muscle'''''
:This muscle shows great species variance and will be explained on their respective pages.
:Function - Extension of the hip, also retraction of the limb and supports outward rotation.

'''''Gluteofemoral Muscle'''''
:This muscle only exists in the cat.
:Function - Retraction and abduction of the limb and hip extension.
:Origin - 2nd-4th caudal vertebrae.
:Insertion - Lateral aspect of patella and fascia lata via an aponeurosis.
:Location - Between the superficial gluteal muscle and biceps muscle of the thigh.

'''''Middle Gluteal Muscle'''''
:This muscle also shows great species variance, though all species have a superficial and deep portion that are separated by a tendinous sheet. Both tendons on their site of insertion are protected by a synovial bursa.
:Function - most powerful extensor of the hip, also abducts and retracts the limb.

'''''Piriform Muscle'''''
:This is fused to the middle gluteal muscle except in carnivores.
:Function - Extensor of hip and abducter of the limb.
:Origin - last sacral vertebrae and sacrotuberous ligament.
:Insertion - just distal to the greater trochanter on the lateral aspect of the femur.
:Location - caudal and medial to the middle gluteal and is covered by the superficial gluteal.

'''Deep Gluteal Muscle'''
:Function - abduction of the limb.
:Origin - lateral aspect of the ilial shaft.
:Insertion - via a short tendon to the greater trochanter.

'''''Tensor Muscle of the Fascia Lata'''''
:This muscle shows great species variance.
:Function - flexion of the hip and extension of the stifle.

===='''The Hamstrings'''====

These muscles cover the caudal aspect of the thigh and are multi-articular. They originate near the ischium and extend to the tibia and have some tendinous components that will make up the '''common calcanean tendon'''.

'''''Biceps Muscle of the thigh'''''
:The largest and most lateral of the muscles, it is superficial and covered only by fascia and skin. It consists of cranial part, arising from the sacrum and sacrotuberous ligament and a small caudal part arising from the ischium. The muscle is composed of multiple parts and has different points of insertion in different species.
:Function - Extension and abduction of the limb. The cranial part extends the hip and stifle, though the caudal part extends the hip but flexes the stifle. It also causes tarsal extension.
:See species pages as is very species specific.

'''''Abductor muscle of the thigh'''''
:Only present in carnivores.
:Function - abduction of the limb.
:Origin - sacrotuberous ligament.
:Insertion - crural fascia.

'''''Semitendinous'''''
:Function - extends the hip, stifle and tarsus when the foot makes contact with the ground, therefore propulsing the animal. On a non-weightbearing leg it flexes the stifle and rotates the leg back and out.
:Origin - the ischial tuberosity ('''pelvic head''').
:Insertion - cranial margin of the tibia and a tendinous insertion on the calcaneal tuberosity.

'''''Semimembranous'''''
:The most medial of the hamstrings.
:Function - Extension of the hip and stifle in a weightbearing stance. On a non-weightbearing limb, it adducts and retracts the limb.
:Origin - can be from either just the pelvic head or from the pelvic head and '''vertebral head'''. This is dependent on species.
:Insertion - onto the medial condyle of the femur and the medial condyle of the tibia.

===='''Medial Muscles of the Thigh'''====

This muscle groups' main functions are to adduct the limb and to prevent unwanted abduction. They lie between the pelvic floor and the medial aspect of the femur.

'''''Sartorius'''''
:Function - flexion of the hip, advancement and abduction of the limb. It can also extend the hip via its attachments to the crural fascia and stifle fascia.
:Origin - Coxal tuberosity; ilial shaft or tendon of psoas minor.
:Insertion - Deep fascia of the leg.
:Location - superficially on the craniomedial border of the thigh as a strap like muscle.

'''''Gracilis'''''
:Function - adductor of the limb, extends the hip.
:Origin - from an aponeurosis of the pelvic symphysis, the insertional tendons of the straight muscle of the abdomen. A tendinous plate is formed between the two aponeurosi of the gracilis' on which the adductor muscles originate.
:Insertion - An aponeurotic insertion with the crural fascia that attaches to the tibial crest.
:Location - broad muscular sheet on the caudal aspect of the medial part of the thigh.

'''''Pectineal Muscle'''''
:Function - flexor of the hip, adductor and supinator of the limb.
:Origin - iliopubic eminence of pelvic floor.
:Insertion - medial border of the femur.
:Location - a fusiform muscle extending between the pecten of the pubis, the pelvic floor and the femur.

'''''Adductor Muscles'''''
:Function - adduction of the limb, can also retract the limb.
:Origin - the tendinous plate of the gracilis muscles.
:Insertion - medial aspect of the femur, fascia and ligaments of the medial aspect of the stifle.

===='''Inner Pelvic Muscles'''====

This set of muscles are a rather mixed group of small muscles lying close to the hip joint. They lie between the pelvis and trochantic fossa of the femur.

'''''Internal Obturator'''''
:Only exists in carnivores and horses.
:Function - extension of the hip and rotation of the femur laterally.
:Origin and insertion - are both dependent on species involved.

'''''External Obturator'''''
:Function - supinator of the femur and adductor of the limb.
:Origin - the ventral pelvic surface close to the obturator foramen.
:Insertion - trochantic fossa.

'''''Gemellus'''''
:Function - rotation of the limb laterally.
:Origin - ischiatic spine.
:Insertion - unites partially with the internal obturator and so inserts on the trochantic fossa.

'''''Quadrate Muscle'''''
:Function - extension of the hip and retraction of the limb.
:Origin - ventral aspect of ischium.
:Insertion - trochantic fossa.

'''''Articular muscle of the hip joint'''''
:Only in carnivores and horses.
:Function - causes tension of the joint capsule and thus helps prevent damage to the peri-articular structures.
:Origin - Hip joint capsule.

===Muscles of the Stifle===

Many of the muscles of the hip (see [[Hindlimb - Anatomy & Physiology#Girdle Musculature|girdle musculature]] and [[Hindlimb - Anatomy & Physiology#Rump Muscles|rump muscles]]) act on the stifle by inserting on structures involved with the stifle or are distal to it. There are only really two muscles that act solely on the stifle; the '''quadriceps''' and the '''popliteal'''.

'''''Quadriceps'''''
:This muscle forms the main muscle bulk on the cranial aspect of the thigh, but is covered by the tensor muscle of the fascia lata, the sartorius and the medial femoral fascia. The quadriceps are the main extensors of the stifle and the straight muscle also flexes the hip. The muscle consists of four parts that have separate points of origin but have a common single tendon, the '''patella tendon''' that inserts onto the patella and '''tibial tuberosity'''.

The four parts are:
:# '''Lateral Vastus''' - On the craniolateral side of the femur, originating from the lateral aspect of the proximal femur.
:# '''Medial Vastus''' - On the craniomedial side of the femur, originating from the medial aspect of the proxial femur.
:# '''Intermediate Vastus''' - On the cranial surface of the femur, it is totally covered by the other quadriceps muscles and is the weakest muscle of the quadriceps.
:# '''Straight muscle/Rectus femoris''' - Originates from the ilial shaft cranial to the acetabulum and runs down to the patella tendon between the two bellies of the lateral and medial vastus.

'''''Popliteal'''''
:Function - flexor of the stifle and pronator of the leg.
:Origin - a tendinous origin from the lateral condyle of the femur.
:Insertion - a broad tendon on the medial and caudal surface of the proximal tibia.
:Location - On the caudal aspect of the stifle and runs under the lateral collateral ligament before it inserts.

{{Template:Learning
|OVAM = [http://www.onlineveterinaryanatomy.net/content/muscle-flashcards-crus-quicktime Muscle flashcards - muscles of the canine hindlimb]<br>[http://www.onlineveterinaryanatomy.net/content/muscle-flashcards-hip-quicktime Muscle flashcards - muscles of the canine hip]
}}

==Vasculature of the Hindlimb==

'''[[Arteries of the Hindlimb - Anatomy & Physiology|Arteries of the Hindlimb]]'''

'''[[Veins of the Hindlimb - Anatomy & Physiology|Veins of the Hindlimb]]'''

'''[[Lymphatics of the Hindlimb - Anatomy & Physiology|Lymphatics of the Hindlimb]]'''

==Innervation of the Hindlimb==

The nerves that supply the hindlimb arise from the lumbosacral plexus, that lies on the medial wall of the pelvis. These nerves are:

'''Femoral Nerve'''
:Origin - cranial part of the lumbosacral plexus, L4 and L5. (Sometimes L3 and L6)
:Motor innervation - Quadriceps and iliopsoas muscle.
:Sensory innervation - the medial aspect of the limb.
:Route - through the iliopsoas.

'''Obturator Nerve'''
:Origin - middle part of the lumbosacral plexus, L5 and L6.
:Motor innervation - adductor muscles; external obturator, adductor and gracilis.
:Sensory innervation - none.
:Route - through the iliopsoas, medial to the ilial shaft and then through the obturator foramen.

'''Gluteal Nerves'''
:Origin - L6, L7 and S1.
:Motor innervation - gluteal muscles, tensor fascia lata, biceps femoris and semitendinosus.
:Sensory innervation - none.
:Route - direct to the gluteals

'''Sciatic Nerve'''
:Origin - L6, L7, S1 and S2.
:Motor innervation - biceps femoris, semintendinosus, semimembranosus.
:Sensory innervation - the nerve divides into the tibial and fibula nerves where cutaneous fibres run.
:Route - the largest nerve in the body. It leaves the pelvis at the greater sciatic notch and curves in a ventral caudal direction around the hip joint. It runs distocaudally over the femur, between the biceps femoris medially and the adductor, semimembranosus and semitendinosus muscles medially. It then divides into the tibial and fibular nerves.

'''Tibial Nerve'''
:Origin - the sciatic nerve.
:Motor innervation - extensors of the hock, flexors of the digits, popliteal muscle.
:Sensory innervation - caudal aspect of the limb below the stifle.
:Route - it runs caudal to the stifle joint into the muscle.

'''Fibular (Peroneal Nerve)'''
:Origin - the sciatic nerve.
:Motor innervation - flexors of the hock, extensors of the digits.
:Sensory innervation - cranial and lateral aspect of the limb.
:Route - caudal to the stifle.

==Species Specifics==

Click here for information on the [[Canine Hindlimb - Anatomy & Physiology|canine hindlimb]].

Click here for information on the [[Bovine Hindlimb - Anatomy & Physiology|bovine hindlimb]].

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[[Category:Musculoskeletal System - Anatomy & Physiology]]
[[Category:A&P Done]]

Joints and Ligaments - Horse Anatomy

2022-10-27T19:23:55Z

Roytwv:

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==[[Forelimb - Anatomy & Physiology|Thoracic Limb]]==
===Shoulder Joint===
The shoulder joint is the articulation between the glenoid cavity of the [[Limb Bones and Cartilages - Horse Anatomy#Scapula|scapula]] and the head of the [[Limb Bones and Cartilages - Horse Anatomy#Humerus|humerus]]. In the horse, lateral and medial movements of this joint are impossible due to the shape of the [[Limb Bones and Cartilages - Horse Anatomy#Humerus|humeral]] head; movement is therefore limited to flexion and extension. The joint is strengthened by the medial and lateral '''glenohumeral ligaments'''. There is also an additional '''coracohumeral ligament''' between the supraglenoid tubercle and the greater tubercle of the [[Limb Bones and Cartilages - Horse Anatomy#Humerus|humerus]].
In the horse, there is no sheath surrounding the bicipital tendon; instead there is an '''intertubercular bursa'''. This bursa lies between the humeral tubercles, cushioning the bicipital tendon, but does not communicate with the cavity of the shoulder joint. The bursa and tendon are held in place by the '''transverse humeral retinaculum''', running between the greater and lesser tubercles of the [[Limb Bones and Cartilages - Horse Anatomy#Humerus|humerus]].

===Elbow Joint===
The elbow joint is the articulation between the [[Limb Bones and Cartilages - Horse Anatomy#Humerus|humeral]] condyle, trochlear notch of the [[Limb Bones and Cartilages - Horse Anatomy#Radius and Ulna|ulna]] and the [[Limb Bones and Cartilages - Horse Anatomy#Radius and Ulna|radial head]]. The joint capsule attaches to the articular surface of the condyle, the periphery of the olecranon fossa and the articular cartilage of the trochlear notch of the [[Limb Bones and Cartilages - Horse Anatomy#Radius and Ulna|ulna]]. Ligaments of the elbow include:
*'''Lateral (radial) collateral ligament''': Attaches to the lateral [[Limb Bones and Cartilages - Horse Anatomy#Humerus|humeral]] epicondyle, the caudal (ulnar) branch is absent in the horse.
*'''Medial (ulnar) collateral ligament''': Attaches to the medial [[Limb Bones and Cartilages - Horse Anatomy#Humerus|humeral]] epicondyle and inserts on the [[Limb Bones and Cartilages - Horse Anatomy#Radius and Ulna|ulna]] and [[Limb Bones and Cartilages - Horse Anatomy#Radius and Ulna|radius]]. The cranial part of the ligament is the remnant of the ''pronator teres'' muscle in horses.

===Carpal Joint===

The carpal joint is a compound joint composed of:
:The '''antebrachiocarpal joint''' between the [[Limb Bones and Cartilages - Horse Anatomy#Radius and Ulna|radius/ulna]] and the proximal [[Limb Bones and Cartilages - Horse Anatomy#Carpal Bones|carpal bones]]
:The '''middle carpal joint''' between the two rows of [[Limb Bones and Cartilages - Horse Anatomy#Carpal Bones|carpal bones]]
:The '''carpometacarpal joint''' between the distal [[Limb Bones and Cartilages - Horse Anatomy#Carpal Bones|carpal bones]] and the proximal [[Limb Bones and Cartilages - Horse Anatomy#Metacarpals and Metatarsals|metacarpals]]

The joint is a synovial joint, comprising a common outer fibrous capsule and three inner synovial pouches, one for each joint. The fibrous joint capsule is strengthened by the '''extensor retinaculum''' on the dorsal aspect and the '''flexor retinaculum''' on the palmar aspect. The '''carpal canal''' houses both the [[Tendons - Horse Anatomy#Flexors|superficial and deep digital flexor tendon]] within a common synovial sheath.

Ligaments supporting the [[Joints and Ligaments - Horse Anatomy#Carpal Joint|carpus ]] include:
*'''Long lateral collateral ligament''': Attaches to the lateral styloid process of the [[Limb Bones and Cartilages - Horse Anatomy#Radius and Ulna|radius]], then divides into a superficial branch and two deep branches. The superficial branch attaches on the [[Limb Bones and Cartilages - Horse Anatomy#Metacarpals and Metatarsals|fourth metacarpal]](lateral splint) and the two deep branches insert on the [[Limb Bones and Cartilages - Horse Anatomy#Carpal Bones|ulnar carpal]] and [[Limb Bones and Cartilages - Horse Anatomy#Carpal Bones|4th carpal]] bones.
*'''Long medial collateral ligament''': Attaches to the medial styloid process of the [[Limb Bones and Cartilages - Horse Anatomy#Radius and Ulna|radius]] then runs to insert on the [[Limb Bones and Cartilages - Horse Anatomy#Metacarpals and Metatarsals|second metacarpal]] (medial splint) bone. A deep branch then detaches to insert on [[Limb Bones and Cartilages - Horse Anatomy#Carpal Bones|2nd carpal]] bone.
*'''Short ligaments''': Join neighbouring [[Limb Bones and Cartilages - Horse Anatomy#Carpal Bones|carpal]] bones either within the same row, or in the adjacent row.

===Metacarpophalangeal (Fetlock) Joint===
The fetlock joint is the articulation between the trochlea of [[Limb Bones and Cartilages - Horse Anatomy#Metacarpals and Metatarsals|third metacarpal]] (cannon bone), the [[Phalanges - Horse Anatomy#Proximal Phalanx|proximal phalanx]] and the proximal sesamoid bones; it allows flexion and extension movements. The joint capsule is divided into a dorsal and palmar pouch. The dorsal pouch extends between [[Limb Bones and Cartilages - Horse Anatomy#Metacarpals and Metatarsals|third metacarpal]] (cannon bone) and the [[Tendons - Horse Anatomy#Extensors|common digital extensor tendon]]. The palmar pouch lies between [[Limb Bones and Cartilages - Horse Anatomy#Metacarpals and Metatarsals|third metacarpal]] (cannon bone) and the suspensory ligament. It has an extensive bursa under the [[Tendons - Horse Anatomy#Extensors|common digital extensor tendon]], continuing a quarter of the length up the [[Limb Bones and Cartilages - Horse Anatomy#Metacarpals and Metatarsals|third metacarpal]]. This joint is associated with a pair of proximal sesamoid bones on the palmar surface. Between the sesamoids, in a groove, lies articular cartilage which articulates with the sagittal ridge of [[Limb Bones and Cartilages - Horse Anatomy#Metacarpals and Metatarsals|third metacarpal]]. The joint capsule runs between all bones in the joint and attaches to the articular cartilage of the sesamoids.

Ligamentous support:
*'''Collateral ligaments''' bind the [[Limb Bones and Cartilages - Horse Anatomy|metacarpal bone]] to the [[Phalanges - Horse Anatomy#Proximal Phalanx|proximal phalanx]], with a deep branch attaching to the sesamoid bone.
*'''Palmar/intersesamoidean ligament''' is a mass of fibrocartilage that embeds the sesamoid bones. The palmar aspect of it forms a groove for the deep flexor tendon to run in, allowing frictionless movement.
*'''Collateral sesamoid ligaments''' connect the outer aspect of the sesamoids to the [[Phalanges - Horse Anatomy#Proximal Phalanx|proximal phalanx]] and there is a distinct branch that attaches to the [[Limb Bones and Cartilages - Horse Anatomy#Metacarpals and Metatarsals|third metacarpal]].
*'''Distal sesamoid ligaments''' are a collection of ligaments that are very marked in the horse and connect the distal surface of the sesamoids to the palmar aspect of the[[Phalanges - Horse Anatomy|phalanx]]. These ligaments include the '''short ligaments''', '''cruciate ligaments''', '''oblique ligament''', '''straight ligament''' and the '''palmar annular ligament'''.
** The '''short ligaments''' connect the axial base of the sesamoids to the lateral/medial aspect on the palmar margin of the [[Phalanges - Horse Anatomy#Proximal Phalanx|proximal phalanx]]. These are the deepest of the ligaments.
** The '''cruciate ligaments''' are paired ligaments from the base of the sesamoids that diagonally cross to attach to the [[Phalanges - Horse Anatomy#Proximal Phalanx|proximal phalanx]]. They lie superficial to the short ligaments.
** The '''oblique ligament''' is a triangular shaped ligament, the base of which attaches to the sesamoids and their interconnecting ligament and the point attaches to the rough palmar aspect of the [[Phalanges - Horse Anatomy#Proximal Phalanx|proximal phalanx]]. It is superficial to the cruciates.
** The '''straight ligament''' proximally attaches like the oblique, but attaches as a flat band to the edge of the complementary fibrocartilage of the proximal end of the [[Phalanges - Horse Anatomy#Middle Phalanx|middle phalanx]].
** The '''palmar annular ligament''' wraps around the sesamoids, [[Tendons - Horse Anatomy#Flexors|flexor tendons]] and their associated sheaths.
<br />

===Proximal Interphalangeal (Pastern) Joint===
The pastern joint, between the trochlea of the [[Phalanges - Horse Anatomy#Proximal Phalanx|proximal phalanx]] and the proximal end of the [[Phalanges - Horse Anatomy#Middle Phalanx|middle phalanx]], allows flexion and extension movements. The palmar border of the [[Phalanges - Horse Anatomy#Middle Phalanx|middle phalanx]] has a complementary fibrocartilage that extends the proximal articular surface of the [[Phalanges - Horse Anatomy#Middle Phalanx|middle phalanx]]. It is sometimes called the middle scutum as it provides a gliding surface for the [[Tendons - Horse Anatomy#Flexors|deep digital flexor tendon]]. The joint capsule is simple and attaches by the articular margins of the two phalanges; blending with the [[Tendons - Horse Anatomy#Extensors|common digital extensor tendon]] dorsally, the collateral ligaments lateral and medially and the straight sesamoidean ligament on the palmar aspect.

The '''collateral ligaments''' connect the distal end of the [[Phalanges - Horse Anatomy#Proximal Phalanx|proximal phalanx]] to the proximal end of the [[Phalanges - Horse Anatomy#Middle Phalanx|middle phalanx]]. They lie in a vertical direction rather than along the bone axis. The fibres of the '''collateral sesamoid ligaments''' of the distal interphalangeal joint run with it, attach to the [[Phalanges - Horse Anatomy#Middle Phalanx|middle phalanx]] and then continue on to their distal attachments. The '''palmar ligaments''' connect the palmar aspect of the distal half of the [[Phalanges - Horse Anatomy#Proximal Phalanx|proximal phalanx]] to the complementary fibrocartilage of the [[Phalanges - Horse Anatomy#Middle Phalanx|middle phalanx]]. These restrict dorsiflexion of the joint. A '''proximal digital annular ligament''' wraps around the superficial surface of the [[Tendons - Horse Anatomy#Flexors|flexor tendons]] and their sheaths at the level of the [[Phalanges - Horse Anatomy#Proximal Phalanx|proximal phalanx]]. There is a distal one also exists that is attached to the [[Phalanges - Horse Anatomy#Proximal Phalanx|proximal phalanx]], it is superficially associated with the digital cushion and is connected to the ergot by the thin fibrous '''ligament of the ergot'''.
<br />

===Distal Interphalangeal (Coffin) Joint===
The coffin joint, between the distal trochlea of the [[Phalanges - Horse Anatomy#Middle Phalanx|middle phalanx]], [[Phalanges - Horse Anatomy#Distal Phalanx|distal phalanx]] and the [[Phalanges - Horse Anatomy#Distal Sesamoid (Navicular) Bone|distal sesamoid ('''navicular bone''')]], allows extension and slight flexion movements. The '''navicular bursa''' lies between the [[Phalanges - Horse Anatomy#Distal Sesamoid (Navicular) Bone|navicular bone]] and the [[Tendons - Horse Anatomy#Flexors|deep digital flexor tendon]]. The joint capsule attaches to the articular periphery and has two pouches, a small dorsal and larger palmar pouch. The dorsal pouch extends under the [[Tendons - Horse Anatomy#Extensors|common digital extensor tendon]] to just proximal of the coronary band. The palmar pouch extends under the [[Tendons - Horse Anatomy#Flexors|deep digital flexor tendon]] to the approximately half way up the [[Phalanges - Horse Anatomy#Middle Phalanx|middle phalanx]]. It dips between the [[Phalanges - Horse Anatomy#Distal Phalanx|distal phalanx]] and sesamoid and bulges laterally where it is related to the collateral ligaments.

The '''collateral ligaments''' connect the distal part of the [[Phalanges - Horse Anatomy#Middle Phalanx|middle phalanx]] to the medial and lateral sides of the proximal [[Phalanges - Horse Anatomy#Distal Phalanx|distal phalanx]] . The '''distal sesamoid ligaments''' connect the distal border of the [[Phalanges - Horse Anatomy#Distal Sesamoid (Navicular) Bone|navicular bone]] to the flexor surface of the [[Phalanges - Horse Anatomy#Distal Phalanx|distal phalanx]] . The '''collateral sesamoid ligaments''' are fibroelastic ligaments that attach to the [[Phalanges - Horse Anatomy#Proximal Phalanx|proximal phalanx]] with the collateral ligaments of the pastern joint and insert to the proximal border of the [[Phalanges - Horse Anatomy#Distal Sesamoid (Navicular) Bone|navicular bone]] . The [[Hoof - Horse Anatomy#Ungual Cartilages|ungual/lateral cartilages]] have a series of ligaments going to the medial/lateral surfaces of the three phalanges and [[Phalanges - Horse Anatomy#Distal Sesamoid (Navicular) Bone|distal sesamoid (navicular bone)]] . There is also a fibrous band connecting the inner surfaces of the cartilages by crossing the superficial aspect of the [[Tendons - Horse Anatomy#Flexors|deep digital flexor tendon]] .

==[[Hindlimb - Anatomy & Physiology|Pelvic Limb]]==
====[[Hindlimb - Anatomy & Physiology#Sacroiliac Joint|Sacroiliac Joint]]====
In horses the short branch of the '''dorsal sacroiliac ligaments''' connects the sacral tuberosity to the spinous processes of the sacrum. The '''sacrotuberous ligament''' is a broad sheet-like ligament, which extends between the transverse processes of the first caudal vertebrae and the dorsal border of [[Hindlimb - Anatomy & Physiology#Ischium|ischium]] and [[Hindlimb - Anatomy & Physiology#Ilium|ilium]]. In this ligament are the '''lesser and greater ischiatic foramen''', these are present to allow for blood vessels, nerves and tendons.

====[[Hindlimb - Anatomy & Physiology#Coxofemoral/Hip Joint|Coxofemoral/Hip Joint]]====
The horse has a limited range of hip movement compared to the dog. This is mainly restricted to flexion and extension and is a result of the conformation of its [[Limb Bones and Cartilages - Horse Anatomy#Femur|femoral head]], intra-articular ligaments and a large muscle mass around the joint. The '''ligament of the femoral head''' extends from the acetabulum to the fovea on the [[Limb Bones and Cartilages - Horse Anatomy#Femur|femoral head]]. Unlike other species, the horse also has an extra ligament present in the joint; the '''accessory ligament'''. The accessory ligament arises from the tendon of insertion of the ''rectus abdominis'' muscle and to a lesser extent ''external abdominal oblique'' muscle as part of the ''prepubic tendon'' and inserts on the fovea. Both ligaments pass through '''acetabular notch'''.

===[[Hindlimb - Anatomy & Physiology#Stifle Joint|Stifle Joint]]===
====Femorotibial Joint====
The femorotibial joint is formed by the [[Limb Bones and Cartilages - Horse Anatomy#Femur|femur]] and [[Limb Bones and Cartilages - Horse Anatomy#Tibia and Fibula|tibia]]. It is divided by '''menisci''' into proximal and distal segments. These communicate through open centres of the menisci where the condyles of the [[Limb Bones and Cartilages - Horse Anatomy#Femur|femur]] and [[Limb Bones and Cartilages - Horse Anatomy#Tibia and Fibula|tibia]] are in contact. The synovial membrane of the joint capsule, which is complete only in the horse, further divides the joint into medial and lateral compartments. The menisci are fibrocartilaginous structures that act as shock absorbers, reducing concussion on the joint as well as incongruency of the articular surfaces. Menisci are attached at the outer margins to the fibrous joint capsule and anchored at their ends mainly on the [[Limb Bones and Cartilages - Horse Anatomy#Tibia and Fibula|tibia]] by the '''cranial and caudal ligaments''', but the lateral meniscus has an additional ligament attaching it to the distal [[Limb Bones and Cartilages - Horse Anatomy#Femur|femur]]. The '''cruciate ligaments''' in the centre of the joint are important for [[Joints and Ligaments - Horse Anatomy#Stifle Joint|stifle]] stability.

====Femoropatellar Joint====
The femoropatellar joint is formed by the [[Limb Bones and Cartilages - Horse Anatomy#Femur|femur]] and [[Hindlimb - Anatomy & Physiology#Patella|patella]]. The [[Hindlimb - Anatomy & Physiology#Patella|patella]] is anchored to the [[Limb Bones and Cartilages - Horse Anatomy#Femur|femur]] by the medial and lateral '''femoropatellar ligaments''' and to the [[Limb Bones and Cartilages - Horse Anatomy#Tibia and Fibula|tibia]] by three patellar ligaments:
*'''Middle Patellar Ligament'''

The middle patellar ligament connects the the cranial aspect of the [[Hindlimb - Anatomy & Physiology#Patella|patella]] apex to the tibial tuberosity. It has two associated bursae; one between the ligament and the groove on the [[Limb Bones and Cartilages - Horse Anatomy#Tibia and Fibula|tibial tuberosity]] and one between the proximal part of the ligament and the [[Hindlimb - Anatomy & Physiology#Patella|patella]] apex. It is palpable just proximal to the [[Limb Bones and Cartilages - Horse Anatomy#Tibia and Fibula|tibial plateaux]].

*'''Lateral Patellar Ligament'''

The lateral patellar ligament attaches to the cranio-lateral aspect of the [[Hindlimb - Anatomy & Physiology#Patella|patella]] and to the lateral aspect of the [[Limb Bones and Cartilages - Horse Anatomy#Tibia and Fibula|tibial tuberosity]]. This arrangement is crucial for the equine [[Stay Apparatus - Horse Anatomy#Pelvic Limb|stay apparatus]] and provides a '''locking ability'''. This ligament contains tendinous tissue from the [[Muscles - Horse Anatomy#Rump Muscles of the Pelvic Limb|''biceps femoris'']] and [[Muscles - Horse Anatomy#Rump Muscles of the Pelvic Limb|''tensor fasciae latae'']] muscles.

*'''Medial Patellar Ligament'''

The medial patellar ligament connects the parapatellar fibrocartilage to the medial aspect of the [[Limb Bones and Cartilages - Horse Anatomy#Tibia and Fibula|tibial tuberosity]] . This ligament contains tendinous elements of the [[Muscles - Horse Anatomy#Rump Muscles of the Pelvic Limb|''sartorius'']] and [[Muscles - Horse Anatomy#Rump Muscles of the Pelvic Limb|''gracilis'']] muscles.

Contraction of the quadriceps while in rest enables the [[Hindlimb - Anatomy & Physiology#Patella|patella]] to be hooked over the trochlea of the [[Limb Bones and Cartilages - Horse Anatomy#Femur|femur]] due to the binding loop formed by the patella, middle and medial patellar ligaments. The '''femeropatellar joint''' capsule sometimes communicates with the '''lateral femerotibial''' cavity and usually with the '''medial'''. No communication exists between the femorotibial joints.

===Tibiofibular Joint===
In the horse, this joint only exists proximally because the distal end of the [[Limb Bones and Cartilages - Horse Anatomy#Tibia and Fibula|fibula]] is fused to the [[Limb Bones and Cartilages - Horse Anatomy#Tibia and Fibula|tibia]] to form the lateral malleolus.

===Tarsal Joint (Hock)===
The hock has four levels of articulation: tarsocrural joint, proximal intertarsal joint, distal intertarsal joint and tarsometatarsal joint. In the horse, the distal three permit almost no movement (high impact, low motion joint).

====Tarsocrural Joint====
In the horse, this joint is formed between the [[Limb Bones and Cartilages - Horse Anatomy#Tibia and Fibula|tibia]] and [[Limb Bones and Cartilages - Horse Anatomy#Tarsal Bones|talus]] only, since the distal end of the [[Limb Bones and Cartilages - Horse Anatomy#Tibia and Fibula|fibula]] is incorporated in the lateral malleolus of the [[Limb Bones and Cartilages - Horse Anatomy#Tibia and Fibula|tibia]]. There is communication with the proximal intertarsal joint.

====Proximal Intertarsal Joint====
Proximally, there is articulation between the [[Limb Bones and Cartilages - Horse Anatomy#Tarsal Bones|talus]] and [[Limb Bones and Cartilages - Horse Anatomy#Tarsal Bones|calcaneus]]. Distally there is articulation between the central and fourth [[Limb Bones and Cartilages - Horse Anatomy#Tarsal Bones|tarsal bones]].

====Distal Intertarsal Joint====
Articulation between the central [[Limb Bones and Cartilages - Horse Anatomy#Tarsal Bones|tarsal bone]] and the numbered [[Limb Bones and Cartilages - Horse Anatomy#Tarsal Bones|tarsal bones]].

====Tarsometatarsal Joint====
Articulation between the small, numbered [[Limb Bones and Cartilages - Horse Anatomy#Tarsal Bones|tarsal bones]] and the [[Limb Bones and Cartilages - Horse Anatomy#Metacarpals and Metatarsals|metatarsals]].

====Ligaments of the Tarsus====
*'''Collateral ligaments''':
**''Long lateral collateral'': Arises from the lateral maleolus of the [[Limb Bones and Cartilages - Horse Anatomy#Tibia and Fibula|tibia]] and terminates on the proximal end of [[Limb Bones and Cartilages - Horse Anatomy#Metacarpals and Metatarsals|metatarsal IV]] (lateral splint). Between these points it attaches to the lateral [[Limb Bones and Cartilages - Horse Anatomy#Tarsal Bones|tarsal bones]].
**''Short lateral collateral'': Deep to the long lateral collateral. It arises from the lateral maleolus of the [[Limb Bones and Cartilages - Horse Anatomy#Tibia and Fibula|tibia]] and attaches via two branches, one to the [[Limb Bones and Cartilages - Horse Anatomy#Tarsal Bones|calcaneus]] and one to the [[Limb Bones and Cartilages - Horse Anatomy#Tarsal Bones|talus]].
**''Long medial collateral'': Arises from the medial malleolus and terminates on the proximal end of [[Limb Bones and Cartilages - Horse Anatomy#Metacarpals and Metatarsals|metatarsal II]] (medial splint). Between these points it attaches to the medial [[Limb Bones and Cartilages - Horse Anatomy#Tarsal Bones|tarsal bones]].
**''Short lateral collateral'': Deep to the long medial collateral. It arises from the medial malleolus and attaches via two branches, one on the [[Limb Bones and Cartilages - Horse Anatomy#Tarsal Bones|calcaneus]] and one on the [[Limb Bones and Cartilages - Horse Anatomy#Tarsal Bones|talus]].
*'''Long plantar ligament''': Extends on the plantar aspect of the hock from the calcaneal tuberosity distally to the proximal end of the third and fourth [[Limb Bones and Cartilages - Horse Anatomy#Metacarpals and Metatarsals|metatarsal bones]] and also attaches to the central and fourth [[Limb Bones and Cartilages - Horse Anatomy#Tarsal Bones|tarsal bones]].

'''The metatarsophalangeal (Fetlock), proximal interphalangeal (Pastern) and distal interphalangeal (Coffin) joints in the pelvic limb are identical to the corresponding joints in the thoracic limb.'''

==Webinars==
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==References==
*Budras, K. Sack, W.O., Anatomy of the Horse, 6th Edition (2012), Schlutersche Verlagsgesellschaft mbH & Co. KG

[[Category:Musculoskeletal System - Horse Anatomy]]

Renal Anatomy - Anatomy & Physiology

2022-10-27T19:21:14Z

Roytwv:

{{OpenPagesTop}}
==Introduction==
The kidneys are paired organs which reside in the dorsal abdomen. One on the left and one on the right. Their role is to filter the blood through the glomerulus to form what is known as the filtrate. This filtrate is then on the whole reabsorbed along the nephron until what is left comprises compounds superfluous to the requirements of the organism. Some compounds, normally fully reabsorbed, are on occasion present in the body in excess. The kidney tubules are able to respond to this excess and excrete such compounds in greater amounts. This is how the kidneys play a major role in the homeostasis of the organism. The kidneys also plays a vital role in the total water balance of the organism. Varying their excretion of water in relation to the hydration status of the animal.

The kidneys receive 25% of the '''cardiac output'''. From this they filter 20% of the plasma forming a filtrate of which all but 1% is reabsorbed. This equates to all the circulatory volume being filtered and reabsorbed every 30 minutes. The functions of the kidneys are to maintain the volume and composition of plasma, regulate water, ion and pH levels, retain nutrients and excrete waste, toxins and excess electrolytes. The kidneys achieve these functions via; glomerular filtration, solute reabsorption, tubular secretion, water balance and acid-base regulation.
[[Image:sagkidlabelled.jpg|right|thumb|250px|<small><center>A labelled saggital section of a lamb kidney(Courtesy of Donal McNally - University of Nottingham)</center></small>]]
==Common Anatomy==
[[Image:basicnormkidap.jpg|right|thumb|250px|<small><center>Histology section of a normal kidney (© RVC 2008)</center></small>]]
[[Image:normkidcortap.jpg|right|thumb|250px|<small><center>Histology section of a normal renal cortex (© RVC 2008)</center></small>]]
[[Image:promaledogab.jpg|right|thumb|250px|<small><center>A prosection of the abdomen of a male dog (© UoN 2008)</center></small>]]
[[Image:profemaledogab.jpg|right|thumb|250px|<small><center>A prosection of the abdomen of a female dog(© UoN 2008)</center></small>]]
* The kidney is the part of the urinary tract where blood is filtered and urine is produced.
* The kidneys are paired and lie in a retroperitoneal position.
* They are positioned in the caudo-dorsal abdomen.
* They lie within a splitting of the sublumbar fascia. This also often contains a large quantity of fat to cushion and protect the kidneys from the pressure of other organs
* The right kidney is most cranial in all species except the pig and grasscutter.
* In species where the right kidney is most cranial it lies in a small fossa of the caudate liver lobe.
* However the left kidney is the most mobile.
* During development all species begin with a multi-lobed structure but a varying degree of fusion occurs between the species giving rise to the various different characteristics seen.

==The Basic Components of the Kidney==

===Outer fibrous capsule===

A tough outer capsule surrounds the parenchyma and this prevents the kidney expanding. It is easily stripped away from a healthy kidney but adheres where pathology has occured.

===Renal Cortex===
* 2 Parts
* External zone
* Internal zone (juxtamedullar)
* Contains the following parts of the [[:Category:Nephron| nephron]]
** [[Nephron Microscopic Anatomy #The Renal Corpuscle| Renal corpuscle]]
** [[Nephron Microscopic Anatomy #Proximal Tubule| Proximal convoluted tubule]]
** [[Nephron Microscopic Anatomy #The Distal Tubule| Distal convoluted tubule]]
** [[WikiWords#Urinary Section| Medullary Rays]]

===Renal Medulla===
[[Image:Aspinall Slide14.JPG|thumb|right|250px|<small>Image from [http://www.elsevierhealth.co.uk/veterinary-nursing/spe-60136/ Aspinall, The Complete Textbook of Veterinary Nursing], Elsevier Health Sciences, ''All rights reserved''</small>]]
* Contains medullary pyramids
* The part nearest the cortex is the base of the pyramid which narrows to form the inner part - renal papilla
* The medulla can be split into two parts, the outer and the inner
* Different parts of the [[:Category:Nephron| nephron]] reside in these areas
====Outer Medulla====
The outer medulla can be further divided into the outer and inner stripe

=====The Outer Stripe=====
This section located just inside the cortex contains the following parts of the [[:Category:Nephron| nephron]]:
* [[Nephron Microscopic Anatomy #Proximal Tubule| Proximal straight tubules]]
* [[Nephron Microscopic Anatomy #The Distal Tubule| Distal straight tubules]]
* [[Nephron Microscopic Anatomy #The Loop of Henle| Thin descending and thick ascending limbs of the loop of henle]]
* [[Nephron Microscopic Anatomy #Collecting Duct| Outer medullary collecting ducts]]
* [[Nephron Microscopic Anatomy #The Vasa Recta| Vasa recta]]

=====The Inner Stripe=====
Located inside of the outer stripe this section contains the following parts:
* [[Nephron Microscopic Anatomy #The Loop of Henle| Thin ascending and thick ascending limbs of the loop of henle]]
* [[Nephron Microscopic Anatomy #Collecting Duct| Outer medullary collecting ducts]]

=====The Difference=====

The outer stripe contains the straight proximal tubules and the inner does not. However the inner contains thin ascending limbs and the outer does not. This difference makes up the anatomical demarcation between the two stripes

====Inner Medulla====
* The inner medulla however only contains the following parts:
** [[Nephron Microscopic Anatomy #The Loop of Henle| Loop of henle]]
** [[Nephron Microscopic Anatomy #Collecting Duct| Collecting ducts]]
** [[Nephron Microscopic Anatomy #The Vasa Recta| Vasa recta]]

===Renal Pelvis===
* The renal sinus is located within an indentation on the medial side of the kidney
* The renal pelvis is located within the renal sinus
* All papillary ducts open here
* The renal pelvis then drains into the ureters
* The renal pelvis is lined with transitional epithelium
* Varies between species
* Absent in cow
* Contains mucous glands in the horse

===Divisions of the Kidney===

* The kidney is divided into [[WikiWords#Urinary Section| renal lobes]] from a structural point of view.
* These can then be divided into a renal pyramid and the piece of cortex above it
* Renal Pyramids are important descriptor of part of the kidney.
**These structures are visible grossly and are the region of the medulla which appears triangular in cross section. They are actually cone shaped and the pointed part which faces towards the renal pelvis is termed the apex and the part against the cortex the base.
* They can also be subdivided into [[WikiWords#Urinary Section| renal lobules]] comprising of [[:Category:Nephron| nephrons]], [[WikiWords#Urinary Section| a medullary ray]] and [[Nephron Microscopic Anatomy #Collecting Duct| a collecting duct]].

* In some species the kidneys are described as '''multipyramidal''' this means they have multiple lobes and pyramids. Others are described as '''unipyramidal''' meaning they only have one lobe and pyramid.

===Innervation===

* Sympathetic and parasympathetic fibres from solar plexus
* Travel with renal arteries
* Sympathetic fibres synapse in coeliac ganglion and cranial mesenteric ganglion

===Lymphatic Drainage===

Renal lymph nodes

==Anatomical Species Differences==
[[Image:lambpigkidcombDM.jpg|right|thumb|250px|<small><center>A picture showing a typical lamb and pig kidney. (Courtesy of Donal McNally - University of Nottingham</center></small>]]
The various species have major and rather striking differences in the structure of their kidneys.

===Canine, Feline, and Ovine===
These species all have similar renal anatomy. Their kidneys are relatively short and thick and they are the traditional kidney bean shape. They have a smooth outer surface and have a single renal papilla. The renal pelvis is large and irregular with recesses which are finger like processes.

The kidney of the feline is relatively bigger than the other species and is quite distinctive because the sub-capsular veins which run towards the hilum are visible. The size of the kidney can be estimated by palpation or via imaging. On a ventrodorsal radiograph, normal kidney size is usually between two to three times the length of second lumbar vertebra, 3 - 4.5 centimetres.

===Bovine===

The kidneys of the bovine do not lose their foetal lobulation. In fact the surface of each kidney is divided into approximately 12 lobules. The right kidney is flattened and ellipsoidal where as the left kidney is thicker at the caudal end than the cranial. Each kidney is surrounded by the capsula adiposa; a layer of fat. Despite what it’s externally lobulated appearance may suggest, the cortex of the bovine kidney is continuous and the kidney is of multipyramidal type. The bovine kidney has no renal pelvis but rather the [[Ureters - Anatomy & Physiology | Ureters]] enters the kidney and divide into a cranial and caudal branch. These branches then subdivide and the papilla at the apex of the pyramids open and drain into these.

The right ureter leaves the kidney and passes along the roof of the abdomen to the pelvis in a fairly standard pattern. The left ureter however moves across the dorsal surface of its kidney to return to the midline and follow a course as if the kidney was located on the left. (both kidneys in the bovine are located on the right see the anatomical landmarks section for further details)

===Porcine===

The kidneys are dorsoventrally flattened. The renal pelvis opens into quite a large space of two major calyces from which bud about 10 minor calyces. These attach to one renal papilla each. The kidneys have a smooth surface.

===Equine===

The equine kidneys not only have very different shapes compared to the rest of the domestic species but they also each have a different shape. The right kidney is described as heart shaped whilst the left is described as being pyramidal. Each organ weighs approximately 700g and both are dorsoventrally flattened. The kidneys are basically unipyramidal and the only demarcation between what were the multiple pyramids of the foetus are the interlobar arteries. This is not always the case in the foal where it is common to be able to identify lobes and the external surface is not always smooth. The horse has a single renal papilla like the dog and its renal pelvis is large and irregular with 2 recesses (finger like processes). The cells of its pelvis secret mucin giving the urine its cloudy appearance.

==Anatomical Landmarks==

Each species has a slightly different orientation of the kidneys within the abdomen.

===Carnivores===

The kidneys in these species are very mobile. Especially the left one and especially in the feline. These anatomical landmarks describe the most common locations. The right kidney is more cranial than the left and tends to lie beneath L1 - L3 where as the left tends to lie under L2-L4. The reason the right kidney is less mobile than the left is that it tends to be almost entirely enclosed within the renal fossa of the caudate lobe of the [[Liver - Anatomy & Physiology|liver]]. The kidneys are enclosed within a layer of fat and this increases with the obesity of the animal.

Medially to the right kidney you will find the caudal vena cava and the right adrenal gland can be found dorsolateral to this structure but still medially to the kidney. Ventrally can be found the Descending [[Duodenum - Anatomy & Physiology|duodenum]] with the right pancreatic limb more towards the ventromedial aspect. In females the right ovary can be found caudoventrally.

The '''Cranial pole''' of the left kidney contacts the [[Monogastric Stomach - Anatomy & Physiology|greater curvature of stomach]] it also contacts the [[Spleen - Anatomy & Physiology|spleen]] on its dorsomedial aspect as well as potentially contacting the left limb of the pancreas. The left adrenal gland can be found at the medial aspect of the cranial pole. The '''Caudal pole''' of the left kidney contacts the [[Small Intestine Overview - Anatomy & Physiology|Small intestine]] and the Descending [[Colon - Anatomy & Physiology|colon]]. At its caudoventral aspect in females is found the left Ovary.

===Ruminants===

Due to the rumen taking up most of the left side of the abdomen it is normal in the bovine to find both of the kidneys on the right side. In the ovine the kidneys are surrounded by very thick masses of fat which reduce the impact of the rumen on their location. The kidneys in the living animal vary their position substantially with respiration and with the pressure of the other organs.

The right kidney has a retroperitoneal attachment to the "sublumbar" musculature. Cranially it touches the liver. In the dead specimen the right kidney occupies the region between the last rib and somewhere between the 2nd and 3rd lumbar vertebrae’s transverse process. The right kidney usually contacts pancreas, duodenum, adrenal glands and colon as well as the afore mentioned liver.

The left kidney in the bovine is to be found caudoventrally to the right one usually in the region between the 2nd and 4th lumbar vertebrae

===Porcine===

The left and right kidneys are more or less aligned in the pig unlike other species. The kidneys of the pig are embedded in lots of fat and lie against the psoas muscle. They span the distance between the last rib cranially and the 4th lumber vertebrae caudally. The '''right kidney''' does not touch the liver unlike other species and is related ventrally to the descending duodenum and jejunum. The '''left kidney''' is ventrally related to the ascending colon, the base of the caecum and the pancreas.

===Equine===

The kidneys of the horse are both enclosed in a fat capsule. Dorsally they rest against the psoas muscle and against the diaphragm.

The right kidney is to be found ventrally to and between the last 2 ribs and first lumbar transverse process. Cranially it touches the liver and caudally it is attached to the pancreas and the base of caecum. The duodenum winds around its lateral and then ventral surfaces. Medially is the caudal vena cava and adrenal gland.

The left kidney is between the last rib and 3rd transverse process. Its ventral surface is almost completely covered by the peritoneum and contacts the small intestine and and small colon. The spleen contacts it cranioventrally. Medially is the left adrenal gland and aorta.

==Renal Blood Supply==

* Supplied by renal arteries
* Arise from aorta
* 3-4mm diameter - dog
* Often divide into dorsal and ventral branches before entering kidney
* Common to find double the normal number - dog

===Left Renal Vessels===

* Left renal artery
** Originates 2cm caudal to the right renal artery
** ~3-4cm long - dog

* Left renal vein
** Immediately ventral to artery
** ~3-4cm long - dog

===Right Renal Vessels===

* Right Renal Artery
** 2cm cranial to left renal artery
** 4 cm caudal to cranial mesenteric artery
** Passes dorsal over the caudal vena cava
** ~4-5cm long - dog

* Right Renal Vein
** Ventral to artery
** ~4-5cm long - dog

===Internal Vascularisation===

Once the renal artery enters the kidney is divides into the interlobar arteries. These pass through the gaps between the renal pyramids as the reach the junctions between the cortex and medullar they branch into the arcuate arteries which move over the base of the pyramids. From these come the interlobular arteries which supply the individual lobules of the cortex. These arteries then branch many times to supply individual glomeruli. The capillaries of the glomerulus then rejoin to form one vessel which then forms the [[Glomerular Apparatus and Filtration - Anatomy & Physiology#Pressure in the Peritubular Capillaries|peritubular capillaries]] of that nephron. The interlobular arteries are examples of end arterioles and there are few anastomoses. Obstruction of one of these arterioles causes ischaemic damage in the kidneys. This is also potentially the case with the interlobar arteries.

{{Learning
|dragster =[[Comparative Kidney Anatomy Dragster resource]]
|flashcards = [[Macroscopic Renal Anatomy - Renal Flash Cards - Anatomy & Physiology]]
|videos = [[Video: Feline Abdomen|Feline Abdomen potcast]]<br>[[Video: Bovine Pregnant Uterus|Bovine pregnant uterus potcast]]<br>[[Video: Bovine liver potcast 2|Bovine liver potcast 2]]<br>[[Video: Feline abdominal and pelvic cavity potcast|Feline abdominal and pelvic cavity potcast]]<br>[[Video: Bovine pregnant uterus potcast 2|Bovine pregnant uterus potcast 2]]<br>[[Video: Lateral view of the pelvic cavity and reproductive tract of the cow potcast|Lateral view of the pelvic cavity and reproductive tract of the cow potcast]]
|OVAM = [http://www.onlineveterinaryanatomy.net/content/urinary-system-and-comparative-kidneys A PowerPoint presentation on the urinary system and comparative kidneys.]
}}

==Webinars==
<rss max="10" highlight="none">https://www.thewebinarvet.com/urogenital-and-reproduction/webinars/feed</rss>
[[Category:Kidney - Anatomy & Physiology]][[Category:Bullet Points]]

Renal Anatomy - Anatomy & Physiology

2022-10-27T19:20:22Z

Roytwv:

{{OpenPagesTop}}
==Introduction==
The kidneys are paired organs which reside in the dorsal abdomen. One on the left and one on the right. Their role is to filter the blood through the glomerulus to form what is known as the filtrate. This filtrate is then on the whole reabsorbed along the nephron until what is left comprises compounds superfluous to the requirements of the organism. Some compounds, normally fully reabsorbed, are on occasion present in the body in excess. The kidney tubules are able to respond to this excess and excrete such compounds in greater amounts. This is how the kidneys play a major role in the homeostasis of the organism. The kidneys also plays a vital role in the total water balance of the organism. Varying their excretion of water in relation to the hydration status of the animal.

The kidneys receive 25% of the '''cardiac output'''. From this they filter 20% of the plasma forming a filtrate of which all but 1% is reabsorbed. This equates to all the circulatory volume being filtered and reabsorbed every 30 minutes. The functions of the kidneys are to maintain the volume and composition of plasma, regulate water, ion and pH levels, retain nutrients and excrete waste, toxins and excess electrolytes. The kidneys achieve these functions via; glomerular filtration, solute reabsorption, tubular secretion, water balance and acid-base regulation.
[[Image:sagkidlabelled.jpg|right|thumb|250px|<small><center>A labelled saggital section of a lamb kidney(Courtesy of Donal McNally - University of Nottingham)</center></small>]]
==Common Anatomy==
[[Image:basicnormkidap.jpg|right|thumb|250px|<small><center>Histology section of a normal kidney (© RVC 2008)</center></small>]]
[[Image:normkidcortap.jpg|right|thumb|250px|<small><center>Histology section of a normal renal cortex (© RVC 2008)</center></small>]]
[[Image:promaledogab.jpg|right|thumb|250px|<small><center>A prosection of the abdomen of a male dog (© UoN 2008)</center></small>]]
[[Image:profemaledogab.jpg|right|thumb|250px|<small><center>A prosection of the abdomen of a female dog(© UoN 2008)</center></small>]]
* The kidney is the part of the urinary tract where blood is filtered and urine is produced.
* The kidneys are paired and lie in a retroperitoneal position.
* They are positioned in the caudo-dorsal abdomen.
* They lie within a splitting of the sublumbar fascia. This also often contains a large quantity of fat to cushion and protect the kidneys from the pressure of other organs
* The right kidney is most cranial in all species except the pig and grasscutter.
* In species where the right kidney is most cranial it lies in a small fossa of the caudate liver lobe.
* However the left kidney is the most mobile.
* During development all species begin with a multi-lobed structure but a varying degree of fusion occurs between the species giving rise to the various different characteristics seen.

==The Basic Components of the Kidney==

===Outer fibrous capsule===

A tough outer capsule surrounds the parenchyma and this prevents the kidney expanding. It is easily stripped away from a healthy kidney but adheres where pathology has occured.

===Renal Cortex===
* 2 Parts
* External zone
* Internal zone (juxtamedullar)
* Contains the following parts of the [[:Category:Nephron| nephron]]
** [[Nephron Microscopic Anatomy #The Renal Corpuscle| Renal corpuscle]]
** [[Nephron Microscopic Anatomy #Proximal Tubule| Proximal convoluted tubule]]
** [[Nephron Microscopic Anatomy #The Distal Tubule| Distal convoluted tubule]]
** [[WikiWords#Urinary Section| Medullary Rays]]

===Renal Medulla===
[[Image:Aspinall Slide14.JPG|thumb|right|250px|<small>Image from [http://www.elsevierhealth.co.uk/veterinary-nursing/spe-60136/ Aspinall, The Complete Textbook of Veterinary Nursing], Elsevier Health Sciences, ''All rights reserved''</small>]]
* Contains medullary pyramids
* The part nearest the cortex is the base of the pyramid which narrows to form the inner part - renal papilla
* The medulla can be split into two parts, the outer and the inner
* Different parts of the [[:Category:Nephron| nephron]] reside in these areas
====Outer Medulla====
The outer medulla can be further divided into the outer and inner stripe

=====The Outer Stripe=====
This section located just inside the cortex contains the following parts of the [[:Category:Nephron| nephron]]:
* [[Nephron Microscopic Anatomy #Proximal Tubule| Proximal straight tubules]]
* [[Nephron Microscopic Anatomy #The Distal Tubule| Distal straight tubules]]
* [[Nephron Microscopic Anatomy #The Loop of Henle| Thin descending and thick ascending limbs of the loop of henle]]
* [[Nephron Microscopic Anatomy #Collecting Duct| Outer medullary collecting ducts]]
* [[Nephron Microscopic Anatomy #The Vasa Recta| Vasa recta]]

=====The Inner Stripe=====
Located inside of the outer stripe this section contains the following parts:
* [[Nephron Microscopic Anatomy #The Loop of Henle| Thin ascending and thick ascending limbs of the loop of henle]]
* [[Nephron Microscopic Anatomy #Collecting Duct| Outer medullary collecting ducts]]

=====The Difference=====

The outer stripe contains the straight proximal tubules and the inner does not. However the inner contains thin ascending limbs and the outer does not. This difference makes up the anatomical demarcation between the two stripes

====Inner Medulla====
* The inner medulla however only contains the following parts:
** [[Nephron Microscopic Anatomy #The Loop of Henle| Loop of henle]]
** [[Nephron Microscopic Anatomy #Collecting Duct| Collecting ducts]]
** [[Nephron Microscopic Anatomy #The Vasa Recta| Vasa recta]]

===Renal Pelvis===
* The renal sinus is located within an indentation on the medial side of the kidney
* The renal pelvis is located within the renal sinus
* All papillary ducts open here
* The renal pelvis then drains into the ureters
* The renal pelvis is lined with transitional epithelium
* Varies between species
* Absent in cow
* Contains mucous glands in the horse

===Divisions of the Kidney===

* The kidney is divided into [[WikiWords#Urinary Section| renal lobes]] from a structural point of view.
* These can then be divided into a renal pyramid and the piece of cortex above it
* Renal Pyramids are important descriptor of part of the kidney.
**These structures are visible grossly and are the region of the medulla which appears triangular in cross section. They are actually cone shaped and the pointed part which faces towards the renal pelvis is termed the apex and the part against the cortex the base.
* They can also be subdivided into [[WikiWords#Urinary Section| renal lobules]] comprising of [[:Category:Nephron| nephrons]], [[WikiWords#Urinary Section| a medullary ray]] and [[Nephron Microscopic Anatomy #Collecting Duct| a collecting duct]].

* In some species the kidneys are described as '''multipyramidal''' this means they have multiple lobes and pyramids. Others are described as '''unipyramidal''' meaning they only have one lobe and pyramid.

===Innervation===

* Sympathetic and parasympathetic fibres from solar plexus
* Travel with renal arteries
* Sympathetic fibres synapse in coeliac ganglion and cranial mesenteric ganglion

===Lymphatic Drainage===

Renal lymph nodes

==Anatomical Species Differences==
[[Image:lambpigkidcombDM.jpg|right|thumb|250px|<small><center>A picture showing a typical lamb and pig kidney. (Courtesy of Donal McNally - University of Nottingham</center></small>]]
The various species have major and rather striking differences in the structure of their kidneys.

===Canine, Feline, and Ovine===
These species all have similar renal anatomy. Their kidneys are relatively short and thick and they are the traditional kidney bean shape. They have a smooth outer surface and have a single renal papilla. The renal pelvis is large and irregular with recesses which are finger like processes.

The kidney of the feline is relatively bigger than the other species and is quite distinctive because the sub-capsular veins which run towards the hilum are visible. The size of the kidney can be estimated by palpation or via imaging. On a ventrodorsal radiograph, normal kidney size is usually between two to three times the length of second lumbar vertebra, 3 - 4.5 centimetres.

===Bovine===

The kidneys of the bovine do not lose their foetal lobulation. In fact the surface of each kidney is divided into approximately 12 lobules. The right kidney is flattened and ellipsoidal where as the left kidney is thicker at the caudal end than the cranial. Each kidney is surrounded by the capsula adiposa; a layer of fat. Despite what it’s externally lobulated appearance may suggest, the cortex of the bovine kidney is continuous and the kidney is of multipyramidal type. The bovine kidney has no renal pelvis but rather the [[Ureters - Anatomy & Physiology | Ureters]] enters the kidney and divide into a cranial and caudal branch. These branches then subdivide and the papilla at the apex of the pyramids open and drain into these.

The right ureter leaves the kidney and passes along the roof of the abdomen to the pelvis in a fairly standard pattern. The left ureter however moves across the dorsal surface of its kidney to return to the midline and follow a course as if the kidney was located on the left. (both kidneys in the bovine are located on the right see the anatomical landmarks section for further details)

===Porcine===

The kidneys are dorsoventrally flattened. The renal pelvis opens into quite a large space of two major calyces from which bud about 10 minor calyces. These attach to one renal papilla each. The kidneys have a smooth surface.

===Equine===

The equine kidneys not only have very different shapes compared to the rest of the domestic species but they also each have a different shape. The right kidney is described as heart shaped whilst the left is described as being pyramidal. Each organ weighs approximately 700g and both are dorsoventrally flattened. The kidneys are basically unipyramidal and the only demarcation between what were the multiple pyramids of the foetus are the interlobar arteries. This is not always the case in the foal where it is common to be able to identify lobes and the external surface is not always smooth. The horse has a single renal papilla like the dog and its renal pelvis is large and irregular with 2 recesses (finger like processes). The cells of its pelvis secret mucin giving the urine its cloudy appearance.

==Anatomical Landmarks==

Each species has a slightly different orientation of the kidneys within the abdomen.

===Carnivores===

The kidneys in these species are very mobile. Especially the left one and especially in the feline. These anatomical landmarks describe the most common locations. The right kidney is more cranial than the left and tends to lie beneath L1 - L3 where as the left tends to lie under L2-L4. The reason the right kidney is less mobile than the left is that it tends to be almost entirely enclosed within the renal fossa of the caudate lobe of the [[Liver - Anatomy & Physiology|liver]]. The kidneys are enclosed within a layer of fat and this increases with the obesity of the animal.

Medially to the right kidney you will find the caudal vena cava and the right adrenal gland can be found dorsolateral to this structure but still medially to the kidney. Ventrally can be found the Descending [[Duodenum - Anatomy & Physiology|duodenum]] with the right pancreatic limb more towards the ventromedial aspect. In females the right ovary can be found caudoventrally.

The '''Cranial pole''' of the left kidney contacts the [[Monogastric Stomach - Anatomy & Physiology|greater curvature of stomach]] it also contacts the [[Spleen - Anatomy & Physiology|spleen]] on its dorsomedial aspect as well as potentially contacting the left limb of the pancreas. The left adrenal gland can be found at the medial aspect of the cranial pole. The '''Caudal pole''' of the left kidney contacts the [[Small Intestine Overview - Anatomy & Physiology|Small intestine]] and the Descending [[Colon - Anatomy & Physiology|colon]]. At its caudoventral aspect in females is found the left Ovary.

===Ruminants===

Due to the rumen taking up most of the left side of the abdomen it is normal in the bovine to find both of the kidneys on the right side. In the ovine the kidneys are surrounded by very thick masses of fat which reduce the impact of the rumen on their location. The kidneys in the living animal vary their position substantially with respiration and with the pressure of the other organs.

The right kidney has a retroperitoneal attachment to the "sublumbar" musculature. Cranially it touches the liver. In the dead specimen the right kidney occupies the region between the last rib and somewhere between the 2nd and 3rd lumbar vertebrae’s transverse process. The right kidney usually contacts pancreas, duodenum, adrenal glands and colon as well as the afore mentioned liver.

The left kidney in the bovine is to be found caudoventrally to the right one usually in the region between the 2nd and 4th lumbar vertebrae

===Porcine===

The left and right kidneys are more or less aligned in the pig unlike other species. The kidneys of the pig are embedded in lots of fat and lie against the psoas muscle. They span the distance between the last rib cranially and the 4th lumber vertebrae caudally. The '''right kidney''' does not touch the liver unlike other species and is related ventrally to the descending duodenum and jejunum. The '''left kidney''' is ventrally related to the ascending colon, the base of the caecum and the pancreas.

===Equine===

The kidneys of the horse are both enclosed in a fat capsule. Dorsally they rest against the psoas muscle and against the diaphragm.

The right kidney is to be found ventrally to and between the last 2 ribs and first lumbar transverse process. Cranially it touches the liver and caudally it is attached to the pancreas and the base of caecum. The duodenum winds around its lateral and then ventral surfaces. Medially is the caudal vena cava and adrenal gland.

The left kidney is between the last rib and 3rd transverse process. Its ventral surface is almost completely covered by the peritoneum and contacts the small intestine and and small colon. The spleen contacts it cranioventrally. Medially is the left adrenal gland and aorta.

==Renal Blood Supply==

* Supplied by renal arteries
* Arise from aorta
* 3-4mm diameter - dog
* Often divide into dorsal and ventral branches before entering kidney
* Common to find double the normal number - dog

===Left Renal Vessels===

* Left renal artery
** Originates 2cm caudal to the right renal artery
** ~3-4cm long - dog

* Left renal vein
** Immediately ventral to artery
** ~3-4cm long - dog

===Right Renal Vessels===

* Right Renal Artery
** 2cm cranial to left renal artery
** 4 cm caudal to cranial mesenteric artery
** Passes dorsal over the caudal vena cava
** ~4-5cm long - dog

* Right Renal Vein
** Ventral to artery
** ~4-5cm long - dog

===Internal Vascularisation===

Once the renal artery enters the kidney is divides into the interlobar arteries. These pass through the gaps between the renal pyramids as the reach the junctions between the cortex and medullar they branch into the arcuate arteries which move over the base of the pyramids. From these come the interlobular arteries which supply the individual lobules of the cortex. These arteries then branch many times to supply individual glomeruli. The capillaries of the glomerulus then rejoin to form one vessel which then forms the [[Glomerular Apparatus and Filtration - Anatomy & Physiology#Pressure in the Peritubular Capillaries|peritubular capillaries]] of that nephron. The interlobular arteries are examples of end arterioles and there are few anastomoses. Obstruction of one of these arterioles causes ischaemic damage in the kidneys. This is also potentially the case with the interlobar arteries.

{{Learning
|dragster =[[Comparative Kidney Anatomy Dragster resource]]
|flashcards = [[Macroscopic Renal Anatomy - Renal Flash Cards - Anatomy & Physiology]]
|videos = [[Video: Feline Abdomen|Feline Abdomen potcast]]<br>[[Video: Bovine Pregnant Uterus|Bovine pregnant uterus potcast]]<br>[[Video: Bovine liver potcast 2|Bovine liver potcast 2]]<br>[[Video: Feline abdominal and pelvic cavity potcast|Feline abdominal and pelvic cavity potcast]]<br>[[Video: Bovine pregnant uterus potcast 2|Bovine pregnant uterus potcast 2]]<br>[[Video: Lateral view of the pelvic cavity and reproductive tract of the cow potcast|Lateral view of the pelvic cavity and reproductive tract of the cow potcast]]
|OVAM = [http://www.onlineveterinaryanatomy.net/content/urinary-system-and-comparative-kidneys A PowerPoint presentation on the urinary system and comparative kidneys.]
}}

<rss max="10" highlight="none">https://www.thewebinarvet.com/urogenital-and-reproduction/webinars/feed</rss>
[[Category:Kidney - Anatomy & Physiology]][[Category:Bullet Points]]

Tongue - Anatomy & Physiology

2022-10-27T19:19:13Z

Roytwv:

{{OpenPagesTop}}
==Introduction==

The tongue (lingua) occupies the ventral aspect of the [[Oral Cavity Overview - Anatomy & Physiology|oral cavity]] and [[Oropharynx - Anatomy & Physiology|oropharynx]]. It is involved with grooming, lapping, prehension and manipulating food in the [[Oral Cavity Overview - Anatomy & Physiology|oral cavity]]. It is also involved in the [[Deglutition|deglutition]] reflex and vocalisation. The tongue is capable of vigorous and precise movements due to the apex being free of attachments to the [[Oral Cavity Overview - Anatomy & Physiology|oral cavity]].
[[Image:Tongue Anatomy Cow.jpg|thumb|right|250px|Tongue Anatomy (Cow) - Copyright Nottingham 2008]]

==Structure and Function==

The tongue is skeletal muscle dorsally and structural fat surrounded by a cartilagenous sheath forming lyssa (canids only) ventrally. It has an attached root and body with a free apex. The '''frenulum''' (fold of mucosa) attaches the body of the tongue to the floor of the [[Oral Cavity Overview - Anatomy & Physiology|oral cavity]]. The root of tongue is attached to the [[Hyoid Apparatus - Anatomy & Physiology|hyoid bone]]. In the horse and dog, the tongue is 'u' shaped, becoming broader towards the tip. The furrow in the centre of the canid tongue is called the '''median sulcus'''. In the ox, sheep and pig the tongue is 'v' shaped with a pointed apex. The '''torus linguae''' is a swelling across the tongue laterally which pushes food against the [[Hard Palate|hard palate]].
[[Image:Tongue Anatomy Cow2.jpg|thumb|right|250px|Tongue Anatomy (Cow) - Copyright Nottingham 2008]]

==Muscles==
[[Image:Tongue Venous Drainage.jpg|thumb|right|250px|Venous Drainage of the Tongue - Copyright Prof. Pat Mccarthy]]

===Intrinsic Muscles===

Intrinsic muscles include the dorsal and ventral longitudinal muscles and the transverse and vertical bundles.

===Extrinsic Muscles===

The extrinsic muscles include:

'''Styloglossus'''

Its origin is at the [[Hyoid Apparatus - Anatomy & Physiology|hyoid apparatus]] (stylohyoid) and it retracts and elevates the tongue.

'''Genioglossus'''

The origin is at the incisive part of the [[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|mandible]]. It protrudes and depressed the tongue.

'''Hyoglossus'''

The origin is at the [[Hyoid Apparatus - Anatomy & Physiology|hyoid apparatus]] (basihyoid). It retracts and depresses the tongue.

'''Geniohyoideus'''

It originates at the incisive part of the [[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|mandible]] and the insertion site is the body of the [[Hyoid Apparatus - Anatomy & Physiology|hyoid]]. It lies below the tongue (not within it) and draws the [[Hyoid Apparatus - Anatomy & Physiology|hyoid]] and therefore the tongue forward.

[[Image:Tongue Muscles Drawing.jpg|thumb|right|250px|Drawing of the Extrinsic Muscles of the Tongue - Copyright nabrown]]

==Innervation==

All muscles moving the tongue are innervated by the hypoglossal nerve ([[Cranial Nerves - Anatomy & Physiology|CN XII]]). The rostral 2/3 of the tongue is innervated by the sensory lingual branch of the trigeminal ([[Cranial Nerves - Anatomy & Physiology|CN V]]) transmitting temperature, touch and pain sensation. The chorda tympani of the facial nerve ([[Cranial Nerves - Anatomy & Physiology|CN VII]]) transmits the taste. The caudal 1/3 of the tongue is innervated by the glossopharyngeal ([[Cranial Nerves - Anatomy & Physiology|CN IX]]) providing sensory function for taste.

==Vasculature==
The main blood supply to the tongue is via the '''lingual artery''', a branch of the external carotid artery. A secondary blood supply to the tongue is provided via the tonsillar branch of the facial artery and the ascending pharyngeal artery.

==Histology==
[[Image:Tongue Histology Cat.jpg|thumb|right|250px|Tongue Histology (Cat) - Copyright RVC 2008]]

The tongue consists of stratified squamous epithelium. There are [[Lingual Gland - Anatomy & Physiology|lingual]] glands and a mucosal covering tightly adheres to the contact surface. The degree of keratinisation depends on the diet. There is less keratinisation on the ventral surface and sides of tongue. It is covered by papillae for protection and taste. Papillae are specialised projections of the mucosa. Some papillae have taste buds, others are mechanical to roughen the surface of the tongue.

==Types of Papillae==

===Conical===
Conical papillae are not found in horses. They are present in the caudal 1/3 of the tongue. They point caudally and have no taste buds. There is a thick epithelium.

[[Image:Foliate_Papillae_Cat.jpg|thumb|right|250px|Foliate Papillae (Cat) - Copyright RVC 2008]]

===Foliate===
Eight to twelve papillae in parallel folds, one either side of the tongue midline. Consists of a stratified squamous epithelium, present in the caudal third of the tongue. There are taste buds, glands and lymphatics present.

===Vallate===
[[Image:Circumvallate Papillae.jpg|thumb|right|250px|Circumvallate Papillae (Goat) - Copyright RVC 2008]]
There are three to six, often secondary papillae in taste buds. There are broad glands in the caudal 1/3 of tongue. Taste buds and lymphatics are present.

===Fungiform===
They form the red dots on tongue surface and consist of keratinised, stratified squamous epithelium and blood vessels. They are involved in loss of heat via panting in dogs. They are present in the rostral 2/3 of the tongue and contain taste buds.

[[Image:Filoform Papillae Histology.jpg|thumb|right|250px|Filoform Papillae Histology (Cat) - Copyright RVC 2008]]

===Filiform===
Filiform papillae are the most numerous and point caudally. There are no taste buds, glands or lymphatics. They are the smallest and consist of a thick keratin on stratified squamous epithelium. They are very prominent in cat and are present in the rostral 2/3 of the tongue.

==[[Gustatory System - Anatomy & Physiology|Taste Buds]]==

Also found on the [[Soft Palate|soft palate]] and the [[Pharynx - Anatomy & Physiology|pharynx]] (but sparsely distributed). There is a constant cell turnover, with flat, thick cells. There are taste hairs (microvilli) pointing through the taste pore. Nerves transduce chemical signals into nervous signals.

==Species Differences==
[[Image:Pig Tongue.jpg|thumb|right|250px|''Pig Tongue'' <br> Pollo 2007, WikiMedia Commons]]
===Canine===
There are stretch receptors in the tongue and they use the tongue to lose heat by panting.

===Ruminant===
The tongue is heavily keratinised with long papillae for eating (protective surface). The ox has lenticular papillae which are hard and horny due to heavy keratinisation.

===Feline===
Feline species have long papillae for grooming, so their tongue is rough.

===Porcine===
Most of the papillae are soft, long and directed caudally.

===[[Avian Tongue - Anatomy & Physiology|Avian]] ===
The avian tongue contains a bone and is mainly used for manipulation of food rather than vocalisation like in mammals. Parrots use the tongue to produce human sounds (see [[Syrinx - Anatomy & Physiology#Species differences|species differences in syrinx]])

==Links==

Click here for [[Tongue - Pathology|pathology of the tongue]] information.
<br>
{{Learning
|flashcards= [[Tongue Anatomy & Physiology Flashcards]]<br>[[Facial_Muscles_-_Musculoskeletal_-_Flashcards|Facial Muscles]]
|powerpoints= [[Oral Cavity Histology resource|Histology of the oral cavity, see part 1 for the tongue]]
|videos = [[Video: Ventral muscles of the head potcast|Ventral muscles of the head potcast]]<br>[[Video: Lateral surface of the head of the dog potcast|Lateral surface of the head of the dog potcast]]<br>[[Video: Lateral surface and sagittal section of the head of a sheep|Lateral surface and sagittal section of the head of a sheep]]<br>[[Video: Lateral surface of the head of the dog potcast 5|Lateral surface of the head of the dog potcast 5]]
|OVAM = [http://www.onlineveterinaryanatomy.net/content/cat-tongue Image - Cat Tongue]
|Vetstream = [https://www.vetstream.com/canis/Content/Disease/dis00702.asp Macroglossia]
}}

==Webinars==
<rss max="10" highlight="none">https://www.thewebinarvet.com/gastroenterology-and-nutrition/webinars/feed</rss>
[[Category:Oral Cavity - Anatomy & Physiology]]

Tongue - Anatomy & Physiology

2022-10-27T19:18:29Z

Roytwv:

{{OpenPagesTop}}
==Introduction==

The tongue (lingua) occupies the ventral aspect of the [[Oral Cavity Overview - Anatomy & Physiology|oral cavity]] and [[Oropharynx - Anatomy & Physiology|oropharynx]]. It is involved with grooming, lapping, prehension and manipulating food in the [[Oral Cavity Overview - Anatomy & Physiology|oral cavity]]. It is also involved in the [[Deglutition|deglutition]] reflex and vocalisation. The tongue is capable of vigorous and precise movements due to the apex being free of attachments to the [[Oral Cavity Overview - Anatomy & Physiology|oral cavity]].
[[Image:Tongue Anatomy Cow.jpg|thumb|right|250px|Tongue Anatomy (Cow) - Copyright Nottingham 2008]]

==Structure and Function==

The tongue is skeletal muscle dorsally and structural fat surrounded by a cartilagenous sheath forming lyssa (canids only) ventrally. It has an attached root and body with a free apex. The '''frenulum''' (fold of mucosa) attaches the body of the tongue to the floor of the [[Oral Cavity Overview - Anatomy & Physiology|oral cavity]]. The root of tongue is attached to the [[Hyoid Apparatus - Anatomy & Physiology|hyoid bone]]. In the horse and dog, the tongue is 'u' shaped, becoming broader towards the tip. The furrow in the centre of the canid tongue is called the '''median sulcus'''. In the ox, sheep and pig the tongue is 'v' shaped with a pointed apex. The '''torus linguae''' is a swelling across the tongue laterally which pushes food against the [[Hard Palate|hard palate]].
[[Image:Tongue Anatomy Cow2.jpg|thumb|right|250px|Tongue Anatomy (Cow) - Copyright Nottingham 2008]]

==Muscles==
[[Image:Tongue Venous Drainage.jpg|thumb|right|250px|Venous Drainage of the Tongue - Copyright Prof. Pat Mccarthy]]

===Intrinsic Muscles===

Intrinsic muscles include the dorsal and ventral longitudinal muscles and the transverse and vertical bundles.

===Extrinsic Muscles===

The extrinsic muscles include:

'''Styloglossus'''

Its origin is at the [[Hyoid Apparatus - Anatomy & Physiology|hyoid apparatus]] (stylohyoid) and it retracts and elevates the tongue.

'''Genioglossus'''

The origin is at the incisive part of the [[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|mandible]]. It protrudes and depressed the tongue.

'''Hyoglossus'''

The origin is at the [[Hyoid Apparatus - Anatomy & Physiology|hyoid apparatus]] (basihyoid). It retracts and depresses the tongue.

'''Geniohyoideus'''

It originates at the incisive part of the [[Skull and Facial Muscles - Anatomy & Physiology#Mandible (mandibula)|mandible]] and the insertion site is the body of the [[Hyoid Apparatus - Anatomy & Physiology|hyoid]]. It lies below the tongue (not within it) and draws the [[Hyoid Apparatus - Anatomy & Physiology|hyoid]] and therefore the tongue forward.

[[Image:Tongue Muscles Drawing.jpg|thumb|right|250px|Drawing of the Extrinsic Muscles of the Tongue - Copyright nabrown]]

==Innervation==

All muscles moving the tongue are innervated by the hypoglossal nerve ([[Cranial Nerves - Anatomy & Physiology|CN XII]]). The rostral 2/3 of the tongue is innervated by the sensory lingual branch of the trigeminal ([[Cranial Nerves - Anatomy & Physiology|CN V]]) transmitting temperature, touch and pain sensation. The chorda tympani of the facial nerve ([[Cranial Nerves - Anatomy & Physiology|CN VII]]) transmits the taste. The caudal 1/3 of the tongue is innervated by the glossopharyngeal ([[Cranial Nerves - Anatomy & Physiology|CN IX]]) providing sensory function for taste.

==Vasculature==
The main blood supply to the tongue is via the '''lingual artery''', a branch of the external carotid artery. A secondary blood supply to the tongue is provided via the tonsillar branch of the facial artery and the ascending pharyngeal artery.

==Histology==
[[Image:Tongue Histology Cat.jpg|thumb|right|250px|Tongue Histology (Cat) - Copyright RVC 2008]]

The tongue consists of stratified squamous epithelium. There are [[Lingual Gland - Anatomy & Physiology|lingual]] glands and a mucosal covering tightly adheres to the contact surface. The degree of keratinisation depends on the diet. There is less keratinisation on the ventral surface and sides of tongue. It is covered by papillae for protection and taste. Papillae are specialised projections of the mucosa. Some papillae have taste buds, others are mechanical to roughen the surface of the tongue.

==Types of Papillae==

===Conical===
Conical papillae are not found in horses. They are present in the caudal 1/3 of the tongue. They point caudally and have no taste buds. There is a thick epithelium.

[[Image:Foliate_Papillae_Cat.jpg|thumb|right|250px|Foliate Papillae (Cat) - Copyright RVC 2008]]

===Foliate===
Eight to twelve papillae in parallel folds, one either side of the tongue midline. Consists of a stratified squamous epithelium, present in the caudal third of the tongue. There are taste buds, glands and lymphatics present.

===Vallate===
[[Image:Circumvallate Papillae.jpg|thumb|right|250px|Circumvallate Papillae (Goat) - Copyright RVC 2008]]
There are three to six, often secondary papillae in taste buds. There are broad glands in the caudal 1/3 of tongue. Taste buds and lymphatics are present.

===Fungiform===
They form the red dots on tongue surface and consist of keratinised, stratified squamous epithelium and blood vessels. They are involved in loss of heat via panting in dogs. They are present in the rostral 2/3 of the tongue and contain taste buds.

[[Image:Filoform Papillae Histology.jpg|thumb|right|250px|Filoform Papillae Histology (Cat) - Copyright RVC 2008]]

===Filiform===
Filiform papillae are the most numerous and point caudally. There are no taste buds, glands or lymphatics. They are the smallest and consist of a thick keratin on stratified squamous epithelium. They are very prominent in cat and are present in the rostral 2/3 of the tongue.

==[[Gustatory System - Anatomy & Physiology|Taste Buds]]==

Also found on the [[Soft Palate|soft palate]] and the [[Pharynx - Anatomy & Physiology|pharynx]] (but sparsely distributed). There is a constant cell turnover, with flat, thick cells. There are taste hairs (microvilli) pointing through the taste pore. Nerves transduce chemical signals into nervous signals.

==Species Differences==
[[Image:Pig Tongue.jpg|thumb|right|250px|''Pig Tongue'' <br> Pollo 2007, WikiMedia Commons]]
===Canine===
There are stretch receptors in the tongue and they use the tongue to lose heat by panting.

===Ruminant===
The tongue is heavily keratinised with long papillae for eating (protective surface). The ox has lenticular papillae which are hard and horny due to heavy keratinisation.

===Feline===
Feline species have long papillae for grooming, so their tongue is rough.

===Porcine===
Most of the papillae are soft, long and directed caudally.

===[[Avian Tongue - Anatomy & Physiology|Avian]] ===
The avian tongue contains a bone and is mainly used for manipulation of food rather than vocalisation like in mammals. Parrots use the tongue to produce human sounds (see [[Syrinx - Anatomy & Physiology#Species differences|species differences in syrinx]])

==Links==

Click here for [[Tongue - Pathology|pathology of the tongue]] information.
<br>
{{Learning
|flashcards= [[Tongue Anatomy & Physiology Flashcards]]<br>[[Facial_Muscles_-_Musculoskeletal_-_Flashcards|Facial Muscles]]
|powerpoints= [[Oral Cavity Histology resource|Histology of the oral cavity, see part 1 for the tongue]]
|videos = [[Video: Ventral muscles of the head potcast|Ventral muscles of the head potcast]]<br>[[Video: Lateral surface of the head of the dog potcast|Lateral surface of the head of the dog potcast]]<br>[[Video: Lateral surface and sagittal section of the head of a sheep|Lateral surface and sagittal section of the head of a sheep]]<br>[[Video: Lateral surface of the head of the dog potcast 5|Lateral surface of the head of the dog potcast 5]]
|OVAM = [http://www.onlineveterinaryanatomy.net/content/cat-tongue Image - Cat Tongue]
|Vetstream = [https://www.vetstream.com/canis/Content/Disease/dis00702.asp Macroglossia]
}}

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[[Category:Oral Cavity - Anatomy & Physiology]]