Thyroid physiology and anatomy 1 Flashcards Preview

Endocrine week 3 > Thyroid physiology and anatomy 1 > Flashcards

Flashcards in Thyroid physiology and anatomy 1 Deck (19):

What is the innervation of the thyroid gland ?

  • Parasympathetic from vagus nerve
  • Sympathetic from superior middle and inferior ganglia of sympathetic trunk 


Describe the blood supply of the thyroid gland 

Superior and inferior thryoid arteries +/- thyroida ima 


Describe the venous drainage of the thyroid gland 

3 pairs of veins - superior/middle thyroid vein ==> internal jugular 

inferior thyroid vein ==> brachiocephalic vein 


What is the thyroid gland supported by ?

Ligaments and strap muscles 


What is the main ligament which supports the thyroid gland ?

The posterior suspensory ligament (berry ligament)


What is there a risk of injuring during surgery on the thyroid ?

  • Injury to the vasculature 
  • Injury to the recurrent laryngeal nerve 


What are the 3 primary features of thyroid glands under the microscope ?

  1. Follicles 
  2. Follicular cells 
  3. Parafollicular cells 


What are follicles in the thyroid ?

Small spherical groupings of cells that consist of a rim of follicular cells which surround the colloid 


What are parafollicular cells ?

Scattered amoung follicular cells and the spaces between follicles 


What is the colloid ?

Tyrosine containing thyroglobulin filled spheres enclosed by follicular cells 


What do follicles play a key role in ?

Thyroid function 


What is the function of follicular cells ?

  1. When stimulated by TSH 
  2. Secrete thyroid hormones T3 and T4 



What is the function of parafollicular cells ?

Secrete calcitonin 


What is the overall idea of synthesis and secretion in the thyroid gland ?

Iodine (the fuel) comes in and then T3/T4 (products) come out 


Describe the stages of synthesis of T3 & T4 

  1. Iodine taken up by follicular cells 
  2. Iodine attaches to tyrosine residues on thyroglobulin to form MIT and DIT
  3. MIT = monoiodotyrosine unit, DIT - Diiodotyrosine unit 
  4. Coupling of MIT and DIT = T3 (triiodotyrosine unit)
  5. Coupling of 2 DIT's = T4 (thyroxine)
  6. T3 and T4 are then stored in colloid till required 


What is the major biologically acitve thyroid hormone ?

T3 - it is roughly 4 times more potnet but 90% of thyroid hormones secreted is T4 


Where is T4 converted to T3 ?

Converted in the liver and kidney 


What is the function of Deiodinase enzymes ?

To either activate or deactivate thyroid hormones 

There is 3 types:

  • D1 
  • D2 
  • D3 


Which Deiodinase enzyme converts T4 into T3 ?

D2 in the tissues