Changes

==Introduction==

==Introduction==

[[Image:smalllargeintestine.jpg|thumb|right|250px|Illustration of the jejunum, caecum, transverse and ascending colon - © RVC 2008]]

[[Image:smalllargeintestine.jpg|thumb|right|250px|Illustration of the jejunum, caecum, transverse and ascending colon - © RVC 2008]]

Remaining water, waste and undigested food is stored as faeces prior to defecation. Defecation is the periodical expulsion of faeces into the environment.

Remaining water, waste and undigested food is stored as faeces prior to defecation. Defecation is the periodical expulsion of faeces into the environment.

'''Defence Against Pathogens:'''

'''Defense Against Pathogens:'''

''Secretions''

''Secretions''

''Epithelium''

''Epithelium''

"Tight junctions" between epithelial cells prevent entry of macromolecules and pathogens into the intestinal tract. Epithelial cells have a very high turnover rate, thus preventing pathogens with a longer life cycle from successfully colonising.

"Tight junctions" between epithelial cells prevent entry of macromolecules and pathogens. Epithelial cells have a very high turnover rate, thus preventing pathogens with a longer life cycle from successfully colonising.

''Commensal flora''

''Commensal flora''

''Movement''

''Movement''

Continuous [http://en.wikipedia.org/wiki/Peristalsis| peristalsis] discourages persistence of toxins and aids in their elimination from the gut.   

Continuous peristalsis discourages persistence of toxins and aids in their elimination from the gut.   

''Cell-mediated and humoural defences''

''Cell-mediated and humoural defenses''

The lamina propria contains macrophages, B and T lymphocytes, plasma cells, and [[Mast Cells|mast cells]]. Lymphoid aggregates known as [[Peyer's Patches - Anatomy & Physiology|Peyer's patches]] within the [[Small Intestine Overview - Anatomy & Physiology|small intestine]] aid in immunity. Secretory [[IgA]] and [[IgM]] provide humoural immunity and help prevent attachment of pathogens to the intestinal epithelium. Lysozyme from Paneth cells inhibits bacterial growth (McGavin & Zachary, 2007).

The lamina propria contains macrophages, B and T lymphocytes, plasma cells, and [[Mast Cells|mast cells]]. Lymphoid aggregates known as [[Peyer's Patches - Anatomy & Physiology|Peyer's patches]] within the [[Small Intestine Overview - Anatomy & Physiology|small intestine]] aid in immunity. Secretory [[IgA]] and [[IgM]] provide humoural immunity and help prevent attachment of pathogens to the intestinal epithelium. Lysozyme from Paneth cells inhibits bacterial growth (McGavin & Zachary, 2007).

Similarly to the [[Small Intestine Overview - Anatomy & Physiology|small intestine]], there are pacemaker cells that generate an action potential. Cells are able to function as a syncytium due to gap junctions, allowing the action potential to spread.

Similarly to the [[Small Intestine Overview - Anatomy & Physiology|small intestine]], there are pacemaker cells that generate an action potential. Cells are able to function as a syncytium due to gap junctions, allowing the action potential to spread.

Contractions are generated in the forward (peristaltic) and backward (antiperistaltic) directions. Antiperistaltic contractions move ingesta into the caecum in some species. The formation of action potentials is under a much stronger neural influence than in the [[Monogastric Stomach - Anatomy & Physiology|stomach]] and [[Small Intestine Overview - Anatomy & Physiology|small intestine]]. The large intestine recieves '''sympathetic''' and '''parasympathetic''' innervation. The sympathetic have coeliac, cranial mesenteric and caudal mesenteric ganglia. As the sympathetic fibres leave the ganglia, they surround their respective artery. Parasympathetic innervation increases the frequency of action potentials and thus stimulates peristalsis. Sympathetic innervation has the opposite effect. Neurones interact with the myenteric plexus to affect contractility, and with the submucosal plexus to affect secretions. Motility of the large intestine increases during meals, possibly as a result of gastrin and cholecystokinin secretion.

Contractions are generated in the forward (peristaltic) and backward (antiperistaltic) directions. Antiperistaltic contractions move ingesta into the caecum in some species. The formation of action potentials is under a much stronger neural influence than in the [[Monogastric Stomach - Anatomy & Physiology|stomach]] and [[Small Intestine Overview - Anatomy & Physiology|small intestine]]. The large intestine receives '''sympathetic''' and '''parasympathetic''' innervation. The sympathetic have coeliac, cranial mesenteric and caudal mesenteric ganglia. As the sympathetic fibres leave the ganglia, they surround their respective artery. Parasympathetic innervation increases the frequency of action potentials and thus stimulates peristalsis. Sympathetic innervation has the opposite effect. Neurones interact with the myenteric plexus to affect contractility, and with the submucosal plexus to affect secretions. Motility of the large intestine increases during meals, possibly as a result of gastrin and cholecystokinin secretion.

==Lymphatics==

==Lymphatics==

[[Image:Colon fox lymphatic nodule.jpg|thumb|right|250px|Lymphatic Nodule - © RVC 2008]]

[[Image:Colon fox lymphatic nodule.jpg|thumb|right|250px|Lymphatic Nodule - © RVC 2008]]

Lymphatic nodules are present in the mucosa of the large intestine. Lymph nodes of the large intestine drain into one of two centres, the '''cranial mesenteric centre''' or the '''caudal mesenteric centre'''. The '''cranial mesenteric centre''' includes lymph nodes of the [[Small Intestine Overview - Anatomy & Physiology|small intestine]] and the following lymph nodes of the large intestine The '''caecal''' - drains the [[Caecum - Anatomy & Physiology|caecum]]. The '''Colic''' - drains the ascending and transverse [[Colon - Anatomy & Physiology|colon]]. The efferent vessels of these lymph nodes converge to form the cranial mesenteric trunk which drains into the chyle cistern. The '''caudal mesenteric centre''' includes the lymph nodes of the descending [[Colon - Anatomy & Physiology|colon]], which are situated in the mesocolon. The efferent vessels of these lymph nodes converge to form the caudal mesenteric trunk which unites with the cranial mesenteric trunk to open into the chyle cistern.

Lymphatic nodules are present in the mucosa of the large intestine. Lymph nodes of the large intestine drain into one of two centres, the '''cranial mesenteric centre''' or the '''caudal mesenteric centre'''. The '''cranial mesenteric centre''' includes lymph nodes of the [[Small Intestine Overview - Anatomy & Physiology|small intestine]] and the following lymph nodes of the large intestine:

 

The '''caecal''' - drains the [[Caecum - Anatomy & Physiology|caecum]].  

 

The '''Colic''' - drains the ascending and transverse [[Colon - Anatomy & Physiology|colon]].  

 

The efferent vessels of these lymph nodes converge to form the cranial mesenteric trunk which drains into the chyle cistern. The '''caudal mesenteric centre''' includes the lymph nodes of the descending [[Colon - Anatomy & Physiology|colon]], which are situated in the mesocolon. The efferent vessels of these lymph nodes converge to form the caudal mesenteric trunk which unites with the cranial mesenteric trunk to open into the chyle cistern.

 

 

 

 

'''Taenia''' may be present. These are concentrations of the '''longitudinal muscle''' layer into long bands. When the taenia contract, they cause shortening of the large intestine, which produces saccualtions, or '''haustra'''. Haustra help to mix the content and to slow the transit time. Many glands are present in the mucosa and skin of the anal region.

==Species Differences==

==Species Differences==

===Carnivore===

===Carnivore===

Digestion is nearing completion by the time chyme enters the large intestine. The dog and cat posses two [[Anus - Anatomy & Physiology#Species Differnces|anal sacs]].

Digestion is nearing completion by the time chyme enters the large intestine. The majority of digestion occurs in the stomach (vomiting undigested bones etc) and small intestine and is reliant on enzymes. The dog and cat posses two [[Anus - Anatomy & Physiology#Species Differences|anal sacs]].

===Ruminant===

===Ruminant===

Digestion is nearing completion by the time chyme enters the large intestine.

Digestion is nearing completion by the time chyme enters the large intestine. In ruminants, which are foregut herbivores, the majority of microbial fermentation occurs in the forestomach which consists of the [[Rumen - Anatomy & Physiology|rumen]], [[Reticulum - Anatomy & Physiology|reticulum]] and [[Omasum - Anatomy & Physiology|omasum]].

===[[Equine Alimentary System  - Anatomy & Physiology|Equine]]===

===[[Alimentary System  - Horse Anatomy|Equine]]===

Most digestion occurs in the large intestine. Taenia are present.

Most digestion occurs in the large intestine. Horses are [[Hindgut Fermenters - Anatomy & Physiology|hindgut fermenting]] herbivores and as a result have a very large [[Alimentary System - Horse Anatomy#Large Intestine|caecum]] where microbial cellulases digest their fibre rich diet. Taenia are present which slow transit and thus aid the digestive process.

===Porcine===

===Porcine===

Taenia are present.

Taenia are present.

==Links==

==Links==

'''Click here for information on [[Intestines, Small and Large - Pathology|pathology of the Small and Large Intestine]]'''

'''Click here for information on [[Intestines, Small and Large - Pathology|pathology of the Small and Large Intestine]]'''

'''Click here for information on [[Diarrhoea]]'''

'''Click here for information on [[Diarrhoea]]'''

'''Video links:'''

{{Template:Learning

 

[http://stream2.rvc.ac.uk/Anatomy/bovine/Pot0048.mp4 Pot 48 The Small and Large intestine of the Ruminant]

|videos = [[Video: Ruminant small and large intestine potcast|Ruminant small and large intestine potcast]]<br>[[Video: Ruminant abdomen potcast|Ruminant abdomen potcast]]<br>[[Video: Foal gastrointestinal tract potcast|Foal gastrointestinal tract potcast]]<br>[[Video: Lateral view of the feline thorax and abdomen potcast|Lateral view of the feline thorax and abdomen potcast]]<br>[[Video: Female dog abdomen dissection|Female dog abdomen dissection]]<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: Ovine large and small intestine dissection|Ovine large and small intestine dissection]]<br>[[Video: Porcine abdomen dissection|Porcine abdomen dissection]]

 

|Vetstream = [https://www.vetstream.com/canis/Content/Disease/dis01059.asp Colitis]

[http://stream2.rvc.ac.uk/Anatomy/bovine/Pot0052.mp4 Pot 52 Lateral view of the Abdomen of a young Ruminant]

 

[http://stream2.rvc.ac.uk/Frean/Pony/left_topography.mp4 Left Sided topography of the Equine abdomen]

[[Category:Large Intestine - Anatomy & Physiology]]

[[Category:Large Intestine - Anatomy & Physiology]]

[[Category:To Do - AimeeHicks]][[Category:To Do - AP Review]]

[[Category:A&P Done]]