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Structures: Part Deux > LEC61: Endrocrine II > Flashcards

LEC61: Endrocrine II Flashcards

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
Q

ID the parathyroid glands

A
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26
Q

where is parathyroid

A

parathyroid is embedded under capsule of thyroid

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27
Q

chief cells fxn

A

secrete the parathyroid hormone

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28
Q

oxyphil cells are?

A

2nd type of cells in parathyroid

do not make hormone

appear during puberty, their # increases with aging

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29
Q

2 types of cells in parathyroid

A

1) chief cells
2) oxyphil cells

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30
Q

identify these cells

A

chief cells, oxyphil cells of parathyroid gland

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31
Q

in older people, what types of cells in parathyroid?

A

chief cells, oxyphil cells, but also FAT cells

32
Q

what is this? ID diff structures

A

older person’s parathyroid, with fat cells taking up 40%

33
Q

what does parathyroid hormone do? how?

A

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
Q

how many adrenal glands?

A

2

35
Q

what are parts of adrenal gland, what are their embryologic origins?

A

cortex- arises from mesoderm

medulla- arises from neural crest

36
Q

ID diff structures

A

adrenal gland- cortex (mesoderm), medulla (neural crest), cortex

37
Q

zones of adrenal cortex and their secretions?

A

zona glomerulosa: mineralcorticoids (aldosterone)

zona fasiculata: glucocorticoids (cortisol)

zona reticularis: androgens

38
Q

what is this

A

zones of the adrenal cortex

39
Q

what is glucocorticoid secretion mediated by, how does it work?

A

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
Q

what is this

A

zona fasiculata of adrenal cortex

secrete glucocorticoids (cortisol)

notice fenestrated capillaries lining columns on both sides b/c ENDOCRINE secretion

41
Q

what regulations glucocorticoid production? how does it work?

A

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
Q

glucocorticoids’ function?

A

regulate carbohydrate, protein, fat metabolism

43
Q

what is this? what does it secrete?

A

zona reticularis

secretes androgens

44
Q

what factors influence histology of adrenal cortex?

A

stress - if high stress, acts on hypothalamis, which acts on pituitary to release ACTH; cortex becomes hypertrophied

45
Q

what factors influence histology of adrenal medulla?

A

none! adrenal medulla is not affected by factors like stress

46
Q

what is this

A

adrenal cortex hypertrophy b/c of stress

47
Q

how do steroid producing cells present?

A

have characteristic organelles - lipid droplets, mitochondria, SER - but don’t store hormones

48
Q

what organelles are involved w/ steroid synthesis in adrenal cortex? what do they do?

A

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
Q

physical relationship btwn adrenal cortex & medulla?

A

not actually connected

50
Q

what are medullary cells considered?

A

modified postganglionic sympathetic neurons

51
Q

what is this

A

adrenal cortex’s zona reticularis, adrenal medulla

52
Q

what are these? fxn?

A

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
Q

what mediates catecholamine secretion?

when does it occur?

what division of autonomic system is release pt of?

what does it lead to?

A

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
Q

blood supplies to adrenal medulla?

A

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
Q

what converts norepinephrine > epinephrine?

A

glucocorticoids

via methylation

56
Q

parts of pancreas?

A

head, neck, body, tail

57
Q

islet of langerhans, function?

A

endocrine part of pancreas

58
Q

how many islets of langerhans in pancreas? where are they?

A

> 1 million islets in pancreas

more islets in tail of pancreas

islets comprise 2% of pancreatic mass

each islet contains ~3000 endocrine cells

59
Q

what is this

A

islets of langerhans

60
Q

what types of cells islets of langerhans contain?

A

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
Q
A

beta cells of islet of langerhans

produce insulin

62
Q
A

alpha cells of islet of langerhans

raise blood glucose

63
Q
A

triple IF staining of islet of langerhans

beta cells-green

alpha cells-red

delta cells-blue

64
Q

what is diffuse endocrine system

A

endocrine cells scattered diffusely in GI tract, ie in villi and crypt of small intestine

65
Q

2 types of enteroendocrine cells

A

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
Q
A

enteroendocrine cell (jejunum)

67
Q

gastrin location, action

A

antrum

increase HCl

68
Q

somatostatin location, action

A

antrum

decrease gastrin

69
Q

CCK location, action

A

duodenum, jejunum

increase pancreatic enzymes

70
Q

secretin location, action

A

duodenum, jejunum

increase pancreatic bicarbonate & water

71
Q

where are enteroendocrine cells in GI tract?

A

antrum, duodenum/jejunum

72
Q

relationship/mechanism of action btwn somatostatin & gastrin?

A

somatostatin inhibits gastrin release

by paracrine mechanism

73
Q

where and how is appetite controlled?

A

satiety center of hypothalamus

GI hormones act on satiety center of hypothalamus, affect appetite

74
Q

what increases appetite?

A

ghrelin - stomach

75
Q

what decreases appetite?

A

leptin - stomach

CCK - duodenum, jejunum

glucagon-like peptide - ileum, colon

PYY - distal ileum, colon

Structures: Part Deux (36 decks)

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