Endo - Thyroid, Para, Pineal

Question 1

thyroid gland structure

Answer 1

2 lobes joined by isthmus
coveredin CT capsule
septa extend in –> form lobules

Question 2

thyroid follicle structure

Answer 2

size based on activity (bigger when active)

stored thyroglobin extracellularly - thick, gelatinous, colloid

Question 3

parafollicular cell structure (+fxn)

Answer 3

located under follicular cells closer towards basal membrane, away from colloid
secrete calcitonin

Question 4

follicular cell structure (basal membrane)

Answer 4

TSH receptor
Na-iodide transporter (NIS)
Na/K ATPase (na out)

Question 5

follicular cell structure (apical)

Answer 5

pendrin (iodide transporter)
thyroid peroxidase (iodidinates thyroglobulin)

Question 6

NIS

Answer 6

transmembrane protein
symporter
cotransports 2 Na and 1 I
driven by Na concentration gradient (from ATPase)

Question 7

thyroglobulin structure

Answer 7

thyroglobulin backbone
tyrosine residue
iodide

Question 8

T3/T4

Answer 8

T3 = MIT + DIT
T4 = DIT + DIT

Question 9

steps of TH synth and release

Answer 9

1. syth and secretion of thyroglobulin into lumen of follicle
2. iodide taken from blood via NIS
3. iodide pumped into lumen via pendrin
4. iodination of thyroglobulin by thyroid peroxidase –> MIT, DIT
5. –> T3, T4 (w/ thyroglobulin backbone)
6. reabsorption of colloid (megalin receptor?)
7. lysosomal breakdown of thyroglobulin
8. release T3 and T4 into blood
9. MIT/DIT converted to iodine and tyrosine and reused

Question 10

TH actions (mito)

Answer 10

up respiration and ox phos
up o2 consumption
up mito gene expression
up mitochondrogenesis
essential role in fetal dev

Question 11

colloid goiter

Answer 11

no iodine, hyperplasia (of follicular cells)

Hashimoto’s thyroiditis

Question 12

exopthalamic goiter

Answer 12

hyperfunction
exopthalamus (also)

Question 13

parathyroid gland location

Answer 13

posterior side of thyroid

4 bean shaped structures

Question 14

regulation of PTH

Answer 14

Ca levels in blood (small changes)

Question 15

parathyroid gland cells

Answer 15

chief cells (aka principle cells)
oxyphil cells

Question 16

chief cells of para (description + fxn)

Answer 16

more basophilic
cyto sometimes looks clear
secrete PTH

Question 17

oxyphil cells (description + fxn)

Answer 17

small condensed nucleus
lots of eosinophilic puffy-looking cyto
no known fxn

Question 18

Ca distribution in body

Answer 18

99% in skeleton

0. 9% intracellular
1. 1% extracellular

Question 19

Ca needed for

Answer 19

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)

Question 20

sites of Ca regulation

Answer 20

bone (deposition/reabsorption)
kidney (regulate excretion)
intestine (regulate absorption)

Question 21

PTH actions

Answer 21

increase bone reabsorption
decrease Ca excretion
up synth of 1,25-dihydroxycholecalciferol (aka calcitrol) - vit D metabolite

Question 22

calcitonin actions

Answer 22

inhibit bone reabsorption (inhibit osteoclasts)

Question 23

making vit D

Answer 23

cholesterol + UV –>
cholecalciferol (D3) + PTH stimulated liver –>
25-hydroxycholecalciferol + PTH stimulated kidney –>
calcitrol

Question 24

actions of calcitrol

Answer 24

increase intestinal absorption of Ca

Question 25

calcium sensing receptor mech

Answer 25

G-protein coupled receptor
high Ca –> binds to receptor, inhibits PTH
low Ca –> no binding, no inhibition

Question 26

pineal gland development

Answer 26

from neuroectoderm

Question 27

pineal gland location

Answer 27

near center of brain

Question 28

pineal gland cell type

Answer 28

pinealocytes

glial cytes

Question 29

corpora arenacea

Answer 29

aka brain sand
calcified concretions that build up in the pineal gland
(precipitates of ca phosphates and carbonates made by the pinealcytes)
light up on CT
help w/ orientation
not pathological
increase w/ age

Question 30

pineal gland fxn

Answer 30

photosensitive
light inhibits pinealcytes to make melatonin
dark stim melatonin
(also include NT and hypo regulating hormones)

Question 31

melatonin actions

Answer 31

inhibit GnRH
–> decrease FSH, LH
+ make you sleepy