Endo - Thyroid, Para, Pineal Flashcards
thyroid gland structure
2 lobes joined by isthmus
coveredin CT capsule
septa extend in –> form lobules
thyroid follicle structure
size based on activity (bigger when active)
stored thyroglobin extracellularly - thick, gelatinous, colloid
parafollicular cell structure (+fxn)
located under follicular cells closer towards basal membrane, away from colloid
secrete calcitonin
follicular cell structure (basal membrane)
TSH receptor
Na-iodide transporter (NIS)
Na/K ATPase (na out)
follicular cell structure (apical)
pendrin (iodide transporter) thyroid peroxidase (iodidinates thyroglobulin)
NIS
transmembrane protein
symporter
cotransports 2 Na and 1 I
driven by Na concentration gradient (from ATPase)
thyroglobulin structure
thyroglobulin backbone
tyrosine residue
iodide
T3/T4
T3 = MIT + DIT T4 = DIT + DIT
steps of TH synth and release
- syth and secretion of thyroglobulin into lumen of follicle
- iodide taken from blood via NIS
- iodide pumped into lumen via pendrin
- iodination of thyroglobulin by thyroid peroxidase –> MIT, DIT
- –> T3, T4 (w/ thyroglobulin backbone)
- reabsorption of colloid (megalin receptor?)
- lysosomal breakdown of thyroglobulin
- release T3 and T4 into blood
- MIT/DIT converted to iodine and tyrosine and reused
TH actions (mito)
up respiration and ox phos up o2 consumption up mito gene expression up mitochondrogenesis essential role in fetal dev
colloid goiter
no iodine, hyperplasia (of follicular cells)
Hashimoto’s thyroiditis
exopthalamic goiter
hyperfunction exopthalamus (also)
parathyroid gland location
posterior side of thyroid
4 bean shaped structures
regulation of PTH
Ca levels in blood (small changes)
parathyroid gland cells
chief cells (aka principle cells) oxyphil cells
chief cells of para (description + fxn)
more basophilic
cyto sometimes looks clear
secrete PTH
oxyphil cells (description + fxn)
small condensed nucleus
lots of eosinophilic puffy-looking cyto
no known fxn
Ca distribution in body
99% in skeleton
- 9% intracellular
- 1% extracellular
Ca needed for
structural stability to bone membrane perm (lack of PTH --> tetany) nerve conduction muscle conduction blood coagulation hormonal secretion reg of enzymes Ca phosphate (bone/teeth)
sites of Ca regulation
bone (deposition/reabsorption)
kidney (regulate excretion)
intestine (regulate absorption)
PTH actions
increase bone reabsorption
decrease Ca excretion
up synth of 1,25-dihydroxycholecalciferol (aka calcitrol) - vit D metabolite
calcitonin actions
inhibit bone reabsorption (inhibit osteoclasts)
making vit D
cholesterol + UV –>
cholecalciferol (D3) + PTH stimulated liver –>
25-hydroxycholecalciferol + PTH stimulated kidney –>
calcitrol
actions of calcitrol
increase intestinal absorption of Ca
