Thyroid anatomy and physiology Flashcards
when does the thyroid gland form in foetus
4 weeks
formation of thyroid gland
Starts off at base of tongue starts descending downwards, goes infront of larynx, migrates all way down to final position- Infront of tracheal rings
Splits into right and left lobe, joined by an isthmus
what does the thyroid gland split into and what is it connected by
right and left lobe connected by isthmus
how may you clinically see a cyst
if you ask patient to move tongue outwards
what do the parathyroid glands secrete
parathyroid
how many parathyroid glands are there
4
thyroid gland and trachea
encricled around it
4 glands at bakc
what hromones does the hyroid produce
thyroxine, calcitonin, t4, t3
uniqueness of thyroid gland
Largest endocrine gland, only lobe that you can palpate, only one that requires substances from environment
what substance from the environment does the thyroidg land need
iodine
basic functional unit of thyroid
follicle
follicular cells
parafollicular cells
which type of cells are follicular cells
cuboidal
where is t3 and t4 produced
follicular cells
where is calcitonin produced
parafollicular cells
negative feedback system
hypothalamus produces TRH - stimulates pituitary to produce thyroid stimulating hormone which stimulates the thyroid gland to produce t3 and t4
what is t4 converted into
active t3
what happens if have appropriate number of thyroid hormones
negative feedback system back to hypothalamus to switch it off so too much isnt produced
what happen sif have too little t3 and 4
increased up regulate hypothalamus and pituitary
where is thyroglobulin produced
in colloid
thyroid hormone synthesis process
Uptake and conc of iodide into follicular cells
Iodide oxidated to iodine
Gets transported into colloid - iodination of thyroigoloubulin
Formation of those two products
Iodine attaches to tyrosine residues to form either mono iodotyrosine unit - one single iodine
Or if two iodines that are attached to thyroglobulin then di-iodotyrosine unit
Mit and dit then have three iodine resisudes in total - t3
If get two di attaching then you get dit and dit- 4 iodine residues- thyroxine
what is most thyroid stored as
t4 - thyroxine
which is more potent t3 or t4
t3
where can t4 be converted to t3
in liver and kidney
is t4 biologically active
no, nly t3 is