4: Pancreas, Thyroid, Parathyroid - Patestas Flashcards
represent the inferior end of teh thyroglossal duct that persists after the remainder of the thyroglossal duct has degenerated
pyramidal lobe of thyroid
present in about 40% of individuals
thyroglossal duct =
developmental remnant: fibrous cord that extends from the fully-developed thyroid gland to foramen cecum in dorsum of tongue
thyroid capsule is derived from..
deep cervical fascia
consists of dense irregular collagneous connective tissue and gives rise to trabecula/septa that partition the gland into lobules
where are parathyroid glands located?
within the capsule covering the posterior surface of the thyroid gland
3 hormones synthesized by the thyroid gland
T3
T4
calcitonin
basic structural and functional unit of the thyroid gland
thyroid follicle
where is glandular secretory product of thyroid stored?
in follicular lumen (extracellulary)
all other endocrine glands accumulate product in the parenchma(within cell)
what type of follicular cell would indicate that highly active?
- simple squamous - low level of activity*
- simple cuboidal - normal level of activity*
- simple columnar - highly active*
vesicles of follicular epithelium contain…
thyroglobulin
parafollicular cells are derived from…
neural crest cells
are parafollicular cells exposed to colloid?
no
they are wedged between follicles and lie within basal lamina surrounding follicle, are near many capillaries
peptide hormone released by parafollicular cells when blood calcium levels are high
calcitonin
how does calcitonin lower blood calcium levels?
- inhibits bone breakdown by osteoclasts
- promotes calcium deposition in bones
follicular lumen contains…
colloid with thyroglobulin and T3 and T4
iodide from the bloodstream is oxidized ____-
on the apical cell membrane facing the colloid into its active form (iodine)
**oxidation of iodide takes place in the active sites of thyroid peroxidase (a membrane-bound enzyme) on the follicular APICAL cell membrane, facing the colloid
where does TSH come from?
anterior pituitary basophils secrete TSH
MIT + DIT = triiodinated tyrosine, when it is cleaved from the thyroglobulin it is called
T3
triiodothyronine
most T3 is produced via..
conversion from T4 by the kidney and heart
follicular cells produce way more T4 than T3
T3 is _____ potent than T4
5 time more potent
metabolic effects of T3
- increase cellular metabolism
- increase growth rate
- increase mental activity
- decrease formation of phospholipid and triglycerides to enhance the production of endogenous cholesterol
increase of thyroid hormone synthesis results in __________ body weight
decreased
increases HR, metabolism, respiration, muscle function and appetite
which cells of the parathyroid gland contain PTH?
chief cells
eosinophilic
the other cells are oxyphil cells and intermediate cells with unknown functions
action of PTH
increases blood calcium level and simultaneously decreases serum phosphate
action of PTH in bone
causes osteoblassts to release osteoclast stimulating factor –> bone breakdown –> increase blood calcium
action of PTH in kidney
prevents calcium loss in urine and promotes phosphate loss in urine
action of PTH in GI
regulates formation of vtiamin D which increases calcium absorption from GI
compete removal of parathyroid glands =
drop blood calcium level (no PTH) –> tetanic contraction of muscles and death
islet of langerhans indicate
endocrine pancreas
alpha cells pancreas =
glucagon (increase blood glucose levels)
beta cells pancreas =
insulin (decrease blood glucose levels)
delta cells pancreas =
somatostatin (inhibits glucagon and insulin) ( reduces GI motility)
when is somatostatin released?
after eating in response to elevation of blood glucose, amino acids or chylomicrons
PP/F cells of pancreas =
pancreatic peptide
inhibits pancreatic exocrine secretions
G cells of pancreas =
gastrin (stimulates HCl by parietal cells)
