The Thyroid Gland Flashcards
What does the thyroid gland weigh?
15-20g
What are the 2 physiologically active forms of thyroid hormone?
T3 (thiiodothyronine)
T4 (thyroxine)
What is T3 also known as?
Thiiodothyronine
What is T4 also known as?
Thyroxine
What are the 2 cell types of the thyroid gland structure?
C (clear cells)
Follicular cells
What is the function of C cells?
Secrete calcitonin (calcium regulating hormone)
What is the function of follicular cells?
Support thyroid hormone synthesis and surround hollow follicles
What are thyroid follicle walls made of?
Follicular cells
What is found inside thyroid follicles?
Colloid (sticky glycoprotein) matrix, contains 2 to 3 months supply of TH
How long a supply of TH is contained in thyroid follicles?
2 to 3 months
What do the follicle cells produce?
Enzymes that make thyroid hormones as well as thyroglobulin (large protein rich in tyrosine residues)
What happens to the enzymes and thyroglobulin that is produced by the follicle cells?
Packaged into vesicles and exported form follicular cells into the colloid
As well as producing enzymes and thyroglobulin, what else to follicular cells do?
Concentrate iodide form plasma and transport it into the colloid where it combines with the tyrosine residues to form the thyroid hormones
Where is iodide and tyrosine derived from?
Diet
What forms together to form the thyroid hormones?
Iodide and tyrosine residues
Explain the process of iodide entering the follicular cell?
Enters follicular cell from plasma via Na+/I- transporter (symport):
1) Coupling to Na enables follicular cells to take up iodide against a concentration gradient
2) Iodide is then transported into the colloid via the pendrin transport