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==Anatomy==

|linkpage =Endocrine System - Anatomy & Physiology

[[Image:Parathyroid Gland Active.jpg|thumb|right|350px|©RVC 2008]]

|linktext =Endocrine System

The parathyroid glands are multiple (generally four) small glands, approximately 1-2mm in length are located about the cranial trachea. Generally, there are two internal glands embedded within the [[Thyroid Gland - Anatomy & Physiology|thyroid Glands]], and two external glands are outside the thyroid tissue. However, all of the parathyroid tissue may be embedded within the thyroid gland itself. In the horse, there are 'nests' of parathyroid tissue along the neck to the thoracic inlet.

|maplink = Endocrine System (Content Map) - Anatomy & Physiology

 

|pagetype =Anatomy

==Embryology==

 

==The Parathyroid Glands==

 

==Histology==

 

 

 

The parathyroid glands are small glands vital for [[Endocrine System - Calcium Homeostasis - Anatomy & Physiology|calcium homeostasis]].

These are the predominant cell type. They stain darker when they are active and are smaller than oxyphil cells. They manufacture Parathyroid Hormone (PTH).

The parathyroid glands are multiple (generally four) small glands approximately 1-2mm in length are located about the cranial trachea.

Oxyphil cells are fewer in number than chief cells. They stain lighter and are larger than chief cells. They have an unknown function.  

Generally there are two internal glands embedded within the [[Endocrine System - Thyroid Gland - Anatomy & Physiology|Thyroid Glands]], and two external glands are outside the thyroid tissue. However all of the parathyroid tissue may be embedded within the thyroid gland itself.

Grossly, the parathyroids are difficult to differentiate from thyroid tissue or fat. A parathyroid gland may be accidentally removed during thyroidectomy. Care must therefore be taken if the second thyroid is removed to leave the parathyroid intact, otherwise [[Hypoparathyroidism|hypoparathyroidism]] may ensue.

* Grossly, the parathyroids are difficult to differentiate from thyroid tissue or fat.

** A parathyroid gland may be accidentally removed during thyroidectomy. Care must therefore be taken if the second thryoid is removed to leave the parathyroid intact, otherwise [[Parathyroid Glands - Pathology|hypoparathyroidism]] may ensue.

====Histology Gallery====

====Histology Gallery====

<center><gallery>

<center><gallery>

Image:Parathyroid Gland Low Power 2.jpg|<p>'''Parathyroid Gland Low Power 2'''</P>^{©RVC 2008}

Image:Parathyroid Gland Low Power 2.jpg|<p>'''Parathyroid Gland Low Power 2'''</P>^{©RVC 2008}

Image:Parathyroid Gland Active.jpg|<p>'''Parathyroid Gland with active Principal Cells'''</P>^{©RVC 2008}

Image:Parathyroid Gland Active.jpg|<p>'''Parathyroid Gland with active Principal Cells'''</P>^{©RVC 2008}

Image:normalparathyroid.jpg|<p>'''Normal Parathyroid Gland'''</P> ^{Image courtesy of of Biomed Image Archive.}

Image:normalparathyroid.jpg|<p>'''Normal Parathyroid Gland'''</P> ^{Image courtesy of Biomed Image Archive.}

</gallery></center>

</gallery></center>

===Blood Supply and Innervation===

==Blood Supply and Innervation==

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===Physiology===

==Physiology==

 

|flashcards = [[Parathyroid_Glands_Flash_Cards_- Anatomy & Physiology|Parathyroid glands]]

|powerpoints = [[Endocrine Histology resource|Histology of the Endocrine system]]

|Vetstream = [https://www.vetstream.com/canis/search?s=parathyroid Parathyroid diseases]

[[Category:Endocrine System - Anatomy & Physiology]]

* When blood calcium levels drop below a certain point, calcium-sensing receptors in the parathyroid gland are activated to release [[Endocrine System - Hormones - Anatomy & Physiology|hormone]] into the blood.

[[Category:A&P Done]]

*The hormone produced by the parathyroid gland (Parathyroid Hormone) also has an effect on [[Endocrine System - Phosphorus Homeostasis - Anatomy & Physiology|Phosphorus Homeostasis]].