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

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==Anatomy==
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|backcolour = FAFAD2
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[[Image:Parathyroid Gland Active.jpg|thumb|right|350px|©RVC 2008]]
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|linkpage =Endocrine System - Anatomy & Physiology
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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.
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|linktext =Endocrine System
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|maplink = Endocrine System (Content Map) - Anatomy & Physiology
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<br>
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==The Parathyroid Glands==
  
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==Embryology==
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The parathyroid glands are small glands vital for [[Calcium Homeostasis - Anatomy & Physiology|calcium homeostasis]].
  
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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.
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==Anatomy==
  
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==Histology==
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The parathyroid glands are multiple (generally four) small glands approximately 1-2mm in length are located about the cranial trachea.
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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.
  
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The parathyroids are histologically easy to distinguish from the thyroid.  
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In the Horse, there are 'nests' of parathyroid tissue along the neck to the thoracic inlet.
  
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The thyroid has a characteristic follicular structure, whereas the parathyroid consists of densely packed cells, of two types:
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===Embryology===
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The parathyroid glands originate from the endoderm of pharyngeal pouches III and IV. The internal gland from pouch IV, external from pouch III.
  
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1. '''Chief cells''' (Principal Cells)
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===Histology===
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These are the predominant cell type. They stain darker when they are active and are smaller than oxyphil cells. They manufacture Parathyroid Hormone (PTH).
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* 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]]
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** The thyroid has a characteristic follicular structure.
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2. '''Oxyphil cells'''
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** The parathyroid consists of densely packed cells, of two types:
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**# Chief cells (Principal Cells)
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Oxyphil cells are fewer in number than chief cells. They stain lighter and are larger than chief cells. They have an unknown function.  
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**#* Are the predominant cell type
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**#* Stain darker when active
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**#* Are smaller than oxyphil cells
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**#* Manufacture Parathyroid Hormone (PTH)
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**# Oxyphil cells
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**#* Are fewer in number than chief cells
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**#* Stain lighter
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**#* Are larger than chief cells
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**#* Have unknown function
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* Grossly, the parathyroids are difficult to differentiate from thyroid tissue or fat.
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** 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.
  
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====Histology Gallery====
  
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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.
 
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====Histology Gallery====
 
  
 
<center><gallery>
 
<center><gallery>
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Image:Parathyroid Gland Low Power 2.jpg|<p>'''Parathyroid Gland Low Power 2'''</P><sup>©RVC 2008</sup>
 
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:Parathyroid Gland Active.jpg|<p>'''Parathyroid Gland with active Principal Cells'''</P><sup>©RVC 2008</sup>
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Image:normalparathyroid.jpg|<p>'''Normal Parathyroid Gland'''</P> <sup> Image courtesy of Biomed Image Archive.</sup>
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Image:normalparathyroid.jpg|<p>'''Normal Parathyroid Gland'''</P> <sup> Image courtesy of of Biomed Image Archive.</sup>
 
</gallery></center>
 
</gallery></center>
  
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==Blood Supply and Innervation==
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===Blood Supply and Innervation===
  
 
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{| border="3" cellpadding="8"
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==Physiology==
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===Physiology===
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* The sole function of the parathyroid gland is to maintain [[Calcium Homeostasis - Anatomy & Physiology|Calcium Homeostasis]].
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** 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.
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* 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.
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*The hormone produced by the parathyroid gland (Parathyroid Hormone) also has an effect on [[Phosphorus Homeostasis - Anatomy & Physiology|Phosphorus Homeostasis]].
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==Test yourself with the Parathyroid Gland Flashcards==
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[[Parathyroid_Glands_Flash_Cards_-_Anatomy_%26_Physiology|Parathyroid Glands Flashcards]]
  
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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]].
 
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<br><br>
 
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{{Template:Learning
 
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|flashcards = [[Parathyroid_Glands_Flash_Cards_- Anatomy & Physiology|Parathyroid glands]]
 
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|powerpoints = [[Endocrine Histology resource|Histology of the Endocrine system]]
 
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|Vetstream = [https://www.vetstream.com/canis/search?s=parathyroid Parathyroid diseases]
 
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}}
 
  
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{{OpenPages}}
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[[Category:Endocrine System]]
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[[Category:Endocrine System - Anatomy & Physiology]]
 
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[[Category:A&P Done]]
 

Revision as of 16:59, 30 August 2010

()Map ENDOCRINE SYSTEM (Map)



The Parathyroid Glands

The parathyroid glands are small glands vital for calcium homeostasis.

Anatomy

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, external from pouch III.

Histology

  • The parathyroids are histologically easy to distinguish from the thyroid.
    ©RVC 2008
    • The thyroid has a characteristic follicular structure.
    • The parathyroid consists of densely packed cells, of two types:
      1. Chief cells (Principal Cells)
        • Are the predominant cell type
        • Stain darker when active
        • Are smaller than oxyphil cells
        • Manufacture Parathyroid Hormone (PTH)
      2. 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 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 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 3rd and 4th 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 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.


Test yourself with the Parathyroid Gland Flashcards

Parathyroid Glands Flashcards

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