Difference between revisions of "Parathyroid Glands - Anatomy & Physiology"

Latest revision as of 20:30, 17 May 2016

Anatomy

©RVC 2008

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 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.

Embryology

The parathyroid glands originate from the endoderm of pharyngeal pouches III and IV. The internal gland from pouch IV and the external from pouch III.

Histology

The parathyroids are histologically easy to distinguish from the thyroid.

The thyroid has a characteristic follicular structure, whereas the parathyroid consists of densely packed cells, of two types:

1. Chief cells (Principal Cells)

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

2. Oxyphil cells

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

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 may ensue.

Histology Gallery

Parathyroid Gland Low Power 1
^{©RVC 2008}
Parathyroid Gland Low Power 2
^{©RVC 2008}
Parathyroid Gland with active Principal Cells
^{©RVC 2008}
Normal Parathyroid Gland
^{Image courtesy of Biomed Image Archive.}

Blood Supply and Innervation

Arteries	Veins	Nerve	Precursor
Superior thyroid artery	Superior thyroid vein	Middle cervical ganglion	Neural crest mesenchyme
Inferior thyroid artery	Middle thyroid vein	Inferior cervical ganglion	3^rd and 4^th pharyngeal pouch endoderm
.</white>	Inferior thyroid vein	.</white>	.</white>

Physiology

The sole function of the parathyroid gland is to maintain calcium homeostasis. Calcium homeostasis is, amongst other things, important for maintaining the function of the nervous and muscular systems. When blood calcium levels drop below a certain point, calcium-sensing receptors in the parathyroid gland are activated to release hormone into the blood. The hormone produced by the parathyroid gland (Parathyroid Hormone) also has an effect on phosphorus homeostasis.

Parathyroid Glands - Anatomy & Physiology Learning Resources
Vetstream To reach the Vetstream content, please select	Canis, Felis, Lapis or Equis
Flashcards Test your knowledge using flashcard type questions	Parathyroid glands
PowerPoint Selection of relevant PowerPoint tutorials	Histology of the Endocrine system

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@@ Line 1: / Line 1: @@
-{{toplink
+{{OpenPagesTop}}
-|backcolour = FAFAD2
+==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==
-}}
-<br>
+The parathyroid glands originate from the endoderm of pharyngeal pouches III and IV. The internal gland from pouch IV and the external from pouch III.
-==The Parathyroid Glands==
+==Histology==
+The parathyroids are histologically easy to distinguish from the thyroid.
+The thyroid has a characteristic follicular structure, whereas the parathyroid consists of densely packed cells, of two types:
+. '''Chief cells''' (Principal Cells)
-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).
-==Anatomy==
+. '''Oxyphil cells'''
-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.
-In the Horse, there are 'nests' of parathyroid tissue along the neck to the thoracic inlet.
-===Embryology===
-The parathyroid glands originate from the endoderm of pharyngeal pouches III and IV. The internal gland from pouch IV, external from pouch III.
-===Histology===
+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.
-* The parathyroids are histologically easy to distinguish from the [[Thyroid Gland - Pathology#Functional anatomy|thyroid]]. [[Image:Parathyroid Gland Active.jpg|thumb|right|350px|©RVC 2008]]
-** The thyroid has a characteristic follicular structure.
-** The parathyroid consists of densely packed cells, of two types:
-**# Chief cells (Principal Cells)
-**#* Are the predominant cell type
-**#* Stain darker when active
-**#* Are smaller than oxyphil cells
-**#* Manufacture Parathyroid Hormone (PTH)
-**# Oxyphil cells
-**#* Are fewer in number than chief cells
-**#* Stain lighter
-**#* Are larger than chief cells
-**#* Have unknown function
-* 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====
 <center><gallery>
@@ Line 46: / Line 32: @@
 Image:Parathyroid Gland Low Power 2.jpg|<p>'''Parathyroid Gland Low Power 2'''</P><sup>©RVC 2008</sup>
 Image:Parathyroid Gland Active.jpg|<p>'''Parathyroid Gland with active Principal Cells'''</P><sup>©RVC 2008</sup>
-Image:normalparathyroid.jpg|<p>'''Normal Parathyroid Gland'''</P> <sup> Image courtesy of of Biomed Image Archive.</sup>
+Image:normalparathyroid.jpg|<p>'''Normal Parathyroid Gland'''</P> <sup> Image courtesy of Biomed Image Archive.</sup>
 </gallery></center>
-===Blood Supply and Innervation===
+==Blood Supply and Innervation==
 {| border="3" cellpadding="8"
@@ Line 73: / Line 59: @@
 |}
-===Physiology===
+==Physiology==
+The sole function of the parathyroid gland is to maintain [[Calcium|calcium homeostasis]]. Calcium homeostasis is, amongst other things, important for maintaining the function of the [[Nervous and Special Senses - Anatomy & Physiology#Nervous System|nervous]] and [[Musculoskeletal System Overview - Anatomy & Physiology|muscular]] systems. When blood calcium levels drop below a certain point, calcium-sensing receptors in the parathyroid gland are activated to release [[Hormones - Anatomy & Physiology|hormone]] into the blood. The hormone produced by the parathyroid gland (Parathyroid Hormone) also has an effect on [[Phosphorus|phosphorus homeostasis]].
+<br><br>
+{{Template:Learning
+|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]
+}}
-* The sole function of the parathyroid gland is to maintain [[Endocrine System - Calcium Homeostasis - Anatomy & Physiology|Calcium Homeostasis]].
+{{OpenPages}}
-** Calcium homeostasis is, amongst other things, important for maintaining function of the [[Nervous and Special Senses - Anatomy & Physiology#Nervous System|nervous]] and [[Musculoskeletal System - Anatomy & Physiology|muscular]] systems.
+[[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]].