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Structures: Part Deux > LEC61: Endrocrine II > Flashcards

LEC61: Endrocrine II Flashcards

(75 cards)

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1
Q

components of endocrine II

A

1) thyroid, C (parafollicular) cells
2) parathyroid
3) adrenal- cortex & medulla
4) pancrease- islets of langerhans
5) diffuse endocrine system

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2
Q

where is thyroid gland?

A

extends from middle of thyroid cartilage > tracheal rings 3-4

has R and L lobes, connected by CT fiber, isthmus, at tracheal ring 1 level

covered by capsule

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3
Q

what are thyroid follicles? contain what? how many are there ?how long do their contents last for?

A

structural unit of lobules of thyroid gland

20 million follicles/lobe of thyroid gland

store sufficient thyroid hormone to last for 3 months

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4
Q

what is in lumen of thyroid follicles?

A

thyroglobulin

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5
Q

what is this? what is in center?

A
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6
Q

what are these

A

thyroid gland’s lobes, lobucles, follicles

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7
Q

what is thyroglobulin?

A

high molecular weight (660 kda) tyrosine-rich glycoprotein

iodinated

for storage of thyroid hormones in lumen of follicles

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8
Q

forms of thyroid hormones? and what are thyroid hormones?

A

T3, triiodothyronine

T4, tetraiodothyronine (thyroxine)

are iodine-containing tyrosine molecules

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9
Q

4 stages of synthesis/storage of thyroid hormones by follicular cells

A

1) follicular cells synthesize thyroglobulin
2) iodide pump at basal plasma membrane uptakes iodide from the blood
3) thyroid peroxidase oxidizes iodide to iodine, at apical plasma membrane
4) tyrosine residues of thyroglobulin in lumen of follicles are iodinated to form T4 and T3

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10
Q

TSH funciotn re: forming T3 and T4

A

TSH controls process of thyroglobulin > T4 and T3

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11
Q

how does T3 triiodothyronine form

A

1 molecule monoiodotyrosine + 1 molecule diiodotyrosine = triiodothyronine, T3

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12
Q

how does thyroxine, T4, form?

A

1 molecule diiodotyrosine + 1 molecule diiodotyrosine = T4, thyroxine

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13
Q

what regulations thyroid hormone production?

A

hypothalamus, anteiror pituitary, and feedback mechanism

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14
Q

difference btwn T3, T4?

A

T3 acts more rapidly, more potent than T4

T4 represents 90% of circulating thyroid hormone

both regulate basal metabolic rate

both influence body growth & maturation, including nerve tissue

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15
Q

describe feedback loop of TRH, TSH, T3 and T4

A

neural stimulus > hypothalamus

hypothalamus produces TRH, acts on anterior pituitary

anterior pitutary secretes TSH

TSH acts on thyroid to make T3 and T4

T3 and T4 effect target tissues

T3 and T4’s production by thyroid acts as negative feedback on hypothalamus and anteiror pituitary

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16
Q

what is thyroid c cell

A

aka parafollicular cells

neuroendocrine cells in the thyroid with primary function to secrete calcitonin

comprise 0.1% of mass of thyroid

derived from neural crest

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17
Q

what is this, what is its fxn

A

thyroid c cells aka parafollicular cells

secrete calcitonin

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18
Q

what is arrow pointing to

A

thyroid c cells aka parafollicular cells

secrete calcitonin

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19
Q

best way to identify c cells?

A

immunohistochemistry with antibody made against calcitonin, which localizes C cell since C cell makes concitonin

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20
Q

what is this

A

immunostaining for C cells using calcitonin ab

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21
Q

what is in the granules

A

calcitonin

c cells/parafollicular cells of thyroid gland

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22
Q

when is calcitonin secreted & what is its effect?

A

is stimulated by high blood calcium levels

suppresses osteoclast activity on bone resorption, so lowers blood calcium levels

opposses action of parathyroid hormone (which raises blood calcium levels)

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23
Q

what type of molecule is calcitonin?

A

a polypeptide

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24
Q

how many parathyroid glands?

A

4

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25
ID the parathyroid glands
26
where is parathyroid
parathyroid is embedded under capsule of thyroid
27
chief cells fxn
secrete the parathyroid hormone
28
oxyphil cells are?
2nd type of cells in parathyroid do not make hormone appear during puberty, their # increases with aging
29
2 types of cells in parathyroid
1) chief cells 2) oxyphil cells
30
identify these cells
chief cells, oxyphil cells of parathyroid gland
31
in older people, what types of cells in parathyroid?
chief cells, oxyphil cells, but also FAT cells
32
what is this? ID diff structures
older person's parathyroid, with fat cells taking up 40%
33
what does parathyroid hormone do? how?
parathyroid hormone raises blood calcium levels. by 1) promotes calcium abroption from intestine, mediated by vitamin D synthesis 2) increases reabsorption of calcium from kidney tubules 3) stimulates bone resorption by osteoclasts w/ release of calcium 4) increases calcium release from bony matrix, due to osteocytic osteolysis
34
how many adrenal glands?
2
35
what are parts of adrenal gland, what are their embryologic origins?
cortex- arises from mesoderm medulla- arises from neural crest
36
ID diff structures
adrenal gland- cortex (mesoderm), medulla (neural crest), cortex
37
zones of adrenal cortex and their secretions?
zona glomerulosa: mineralcorticoids (aldosterone) zona fasiculata: glucocorticoids (cortisol) zona reticularis: androgens
38
what is this
zones of the adrenal cortex
39
what is glucocorticoid secretion mediated by, how does it work?
renin-angiotensin-aldosterone system mediates secretion decreased bp acts on kidney distal tubules, causes decreased [Na] decreased [Na] causes kidney to secrete renin renin acts on other systems, to produce angiotensin II, vascoconstrictor angiotensis II acts on zona glomerulosa to stimulate aldosterone secretion aldosterone goes to kidney tubules to increase Na reabsorption in tubules Na reabsorption in kidney tubules \> increased bp!
40
what is this
zona fasiculata of adrenal cortex secrete glucocorticoids (cortisol) notice fenestrated capillaries lining columns on both sides b/c ENDOCRINE secretion
41
what regulations glucocorticoid production? how does it work?
hypothalamis, anterior pituitary, feedback mechanism hypothalamus secretes CRH. this acts on anterior pituitary. anterior pituitary releases ACTH into circulation ACTH in circulation causes adrenal cortex to secrete glucocorticoids glucocorticoids' secretion has negative feedback on hypothalamus and anterior pituitary
42
glucocorticoids' function?
regulate carbohydrate, protein, fat metabolism
43
what is this? what does it secrete?
zona reticularis secretes androgens
44
what factors influence histology of adrenal cortex?
stress - if high stress, acts on hypothalamis, which acts on pituitary to release ACTH; cortex becomes **hypertrophied**
45
what factors influence histology of adrenal medulla?
none! adrenal medulla is not affected by factors like stress
46
what is this
adrenal **cortex** hypertrophy b/c of stress
47
how do steroid producing cells present?
have characteristic organelles - lipid droplets, mitochondria, SER - but don't store hormones
48
what organelles are involved w/ steroid synthesis in adrenal cortex? what do they do?
mitochondrion- form intermediates from cholesterol, pass to smooth ER; after processing in smooth ER, forms steroid hormones like aldosterone, cortisol, which \> circulation smooth ER- processes intermediates "shuttle mechanism" of mitochondrion \> smooth ER \> mitochondrion
49
physical relationship btwn adrenal cortex & medulla?
not actually connected
50
what are medullary cells considered?
modified postganglionic sympathetic neurons
51
what is this
adrenal cortex's zona reticularis, adrenal medulla
52
what are these? fxn?
adrenal medulla cells synthesize catecholamines, which stain brown when exposed to chromium, so call medullary cells "chromaffin" cells lighter= epinephrine (aka A cells, 80%), darker= norepinephrine (aka N cells, 20%)
53
what mediates **_catecholamine_** secretion? when does it occur? what division of autonomic system is release pt of? what does it lead to?
1) mediated by preganglion sympathetic fibers that innervate chromaffin cells 2) occurs in resposne toa acute fear, stress 3) constitutes "fight or flight" response - sympathetic 4) leads to increased bp, faster heart rate, faster breathing rate, elevated blood glucose levels
54
blood supplies to adrenal medulla?
1) long cortical arteries- supply bed directly to medulla 2) short cortical arteries- carry glucocorticoids from cortex to medulla; pass through zona glomerulosa, zona fasiculata, zona reticularis before \> adnreal medulla
55
what converts norepinephrine \> epinephrine?
glucocorticoids via methylation
56
parts of pancreas?
head, neck, body, tail
57
islet of langerhans, function?
endocrine part of pancreas
58
how many islets of langerhans in pancreas? where are they?
\> 1 million islets in pancreas more islets in tail of pancreas islets comprise 2% of pancreatic mass each islet contains ~3000 endocrine cells
59
what is this
islets of langerhans
60
what types of cells islets of langerhans contain?
1) **_beta-cells_**: insulin-producing cells, lower blood glucose 2) **_alpha-cells_**: glucagon-producing cells, raise blood glucose 3) **_delta-cells:_** somatostatin, inhibits insulin and/or glucagon secretion via paracrine mechanism 4) **_PP cells_**: pancreatic polypeptide cells, inhibits pancreatic enzyme secretion
61
beta cells of islet of langerhans produce insulin
62
alpha cells of islet of langerhans raise blood glucose
63
triple IF staining of islet of langerhans beta cells-green alpha cells-red delta cells-blue
64
what is diffuse endocrine system
endocrine cells scattered diffusely in GI tract, ie in villi and crypt of small intestine
65
2 types of enteroendocrine cells
endocrine cells of the GI tract and pancreas (islet of langerhans) open type: microvilli on lumen of intestine closed type in both types, cells released into bloodstream or tissue space, not through apex of cell into intestinal lumen
66
enteroendocrine cell (jejunum)
67
gastrin location, action
antrum increase HCl
68
somatostatin location, action
antrum decrease gastrin
69
CCK location, action
duodenum, jejunum increase pancreatic enzymes
70
secretin location, action
duodenum, jejunum increase pancreatic bicarbonate & water
71
where are enteroendocrine cells in GI tract?
antrum, duodenum/jejunum
72
relationship/mechanism of action btwn somatostatin & gastrin?
somatostatin inhibits gastrin release by paracrine mechanism
73
where and how is appetite controlled?
satiety center of hypothalamus GI hormones act on satiety center of hypothalamus, affect appetite
74
what increases appetite?
ghrelin - stomach
75
what decreases appetite?
leptin - stomach CCK - duodenum, jejunum glucagon-like peptide - ileum, colon PYY - distal ileum, colon

Structures: Part Deux (36 decks)

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