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Histology Exam 3 > 22- Endocrine System 2 > Flashcards

22- Endocrine System 2 Flashcards

1
Q

Thyroid gland

A 
bilobed gland 
Septa divide loves into lobules
About 25-40 grams
2 lobes are connected by an isthmus
gland lies in the anterior region of neck, inferior to larynx
Thin CT capsule surrounding it
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2
Q

Follicular/principal cells

A

are the secretory cells
form follicles (hollow spheres with a central cavity)
follicles are .02-.9 mm in diameter

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3
Q

The follicular lumen is filled with a substance called

A

Colloid- contains proteolytic enzymes, thyroglobulin, and mucoproteins

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4
Q

Parafollicular/ C cell

A

second type of secretory cell
found in the wall of the follicle or between follicles
Parafollicular cells are identified by their location rather than by their appearance
In LM they are similar in appearance to follicular cells

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5
Q

Blood supply to thyroid

A

fenestrated capillaries from thyroid arteries

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6
Q

Nerve supply to thymus

A

Postganglionic sympathetic fibers to blood vessels

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7
Q

Follicular cells (principal cells) form

A

the wall of the follicles

  • surrounded by basal lamina at their periphery
  • have round and prominent nuclei
  • their hight in a follicle is directly proportional to the activity of the follicle (lower epithelium, more squamous means less active follicle)
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8
Q

Inactive follicles have more

A

stored colloid

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9
Q

Follicular cells secrete

A 
thyroid hormones T3 (triiodothyroninie) 
and T4 (tetra-iodothyronine)
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10
Q

Follicular cells synthesize

A

thyroglobulin (which is released into the lumen of the follicle where it is iodinated)

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11
Q

Iodinated thyroglobulin is stored

A

in the follicular lumen

When needed, thyroglobulin is taken up by endocytosis back into the follicular cells

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12
Q

Thyroglobulin is hydrolyzed in the follicular cells to release

A

T3 and T4
T3 and T4 are released from the basal surface of the follicular cells into the interstitum, where they diffuse into blood and lymph capillaries

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13
Q

T3 and T4 regulate

A

metabolism

T3 and T4 production is controlled by a feedback system that works through the hypothalamus

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14
Q

Low levels of T3 and T4

A

cause the release of thyroid releasing hormone (TRH) from the hypothalamus
TRH causes release of TSH from the adenohypophysis into the blood

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15
Q

TSH reaches the thyroid, where it stimulates

A

production and release of T3 and T4; levels of T3 and T4 in circulating blood control TRH release

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16
Q

Levels of T3 and T4 in blood control release of

A

TRH

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17
Q

Parafollicular cells

A
  • Lie in the follicle wall or between follicles
  • Forms part of the follicular wall
  • Parafollicular cell never directly contacts the colloid in the lumen of the cell
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18
Q

Parafollicular cells release

A

the hormone thryocalcitonin (calcitonin)

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19
Q

Thryocalcitonin does what?

A

lowers blood calcium by inhibiting bone resorption and increasing calcium absorption by bone

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20
Q

Thyrocalcitonin release is directly regulated by

A

blood calcium levels
High calcium levels stimulates its release
(so it’s taken from the blood up into the bone)

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21
Q

Simple hypertrophy of the thyroid gland is called

A

goiter, it’s most commonly caused by an iodine-deficient diet

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22
Q

Inflammatory disease of the thyroid gland (thyroiditis) may be caused by

A

a virus, or be the result of an autoimmune reaction (Hashimoto’s thyroiditis)

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23
Q

Excessive activity of the thyroid gland is called

A

hyperthyroidism (thyrotoxicosis or Grave’s disease)

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24
Q

In hyperthyroidism (Grave’s disease) hyperfunction of the thyroid is the result of

A

a defect in the immune system, with production of a circulating immunoglobulin that binds to the follicular cells and mimics the effects of TSH

It is characterized by weight loss, increased heart rate, nervousness, and protrusion of the eyeballs (exophthalmos)

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25
Q

Hypothyroidism is

A

abnormally low levels of production of thyroid hormones
In adults, the condition is called myxedema, and it may be the result of an autoimmune disorder, such as Hashimoto’s thyroiditis, which destroys thyroid tissue

Characterized by weight gain, non-pitting edema of the skin, dry and cold skin, constipation, decreased heart rate, and enlargement of the tongue

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26
Q

Children who are hypothyroid from birth, usually from non-development of a thyroid gland, have a condition called

A

cretinism

Cretins have arrested physical and mental development both before and after birth
Prior to birth, the fetus receives some thyroid hormones via placental transfer from the mother.
The defects in cretinism are more severe if the mother also has a thyroid deficiency

27
Q

Parathyroid gland

A
  • glands are embedded in the posterior surface of the thyroid gland
  • Usually 2 pairs (4 total)
  • pea sized
  • Have secretory cells in the form of cords
28
Q

2 cell types of parathyroid gland

A

Chief (principal) cells

Oxyphil cells

29
Q

The parathyroid gland is surrounded by

A

a thin connective tissue capsule with septa
The connective tissue component of the gland increases with age, especially the fat
In elderly, the gland is 60-70% fat

30
Q

Blood supply to parathyroid gland

A

fenestrated capillaries from the thyroid arteries

31
Q

Nerve supply to parathyroid gland

A

postganglionic sympathetic to blood vessels

32
Q

Chief cells

A

presumptive hormone secretors
vesicular (open faced) nucleus
water clear (pale staining) cytoplasm

33
Q

Oxyphil cell

A 
less common, found in clumps or singly
not many found until puberty; increase in number with age
larger than chief cells 
eosinophilic cytoplasm
smaller, heterochromatic nucleus
may be a stage of chief cell development
34
Q

Hormone secreted by chief cells

A

parathyroid hormone (PTH)

35
Q

Parathyroid hormone does what?

A

Increases blood calcium levels
increases calcium release from bone
stimulates calcium resorption by kidney (by regulating the conversion of vitamin D3 to its active form)
increases calcium absorption from gut

36
Q

Parathyroid hormone release is directly controlled by

A

blood calcium levels

LOW levels stimulate secretion of PTH

37
Q

Parathyroid glands are essential for life. Removal of the parathyroid gland (thyroidectomy) will result in

A

tetanic contraction of muscles due to the drop in blood calcium
Contraction of the muscles related to respiration will cause death

38
Q

Hyperparathyroidism is characterized by

A

increased blood calcium levels, resulting in pathologic deposits of calcium in organs such as the kidney and arteries

39
Q

Hypoparathyroidism is characterized by

A

decreased blood calcium levels, with increased bone density

The decreased circulation of calcium levels cause skeletal muscles to undergo spastic contractions called tetany

40
Q

Adrenal (Suprarenal) Gland

A

flattened triangular bodies found at the superior pole of each kidney
Each gland has a cortex and medulla
Has thick CT capsule with septa

41
Q

Adrenal Cortex

A 
essential for life 
Divided into 3 zones: 
Zona glomerulosa (15%)- thin region under capsule
Zona fasciculata (80%)- middle region, usually thickest
Zona reticularis (5-7%)- region directly adjacent to medulla
42
Q

Adrenal medulla

A

not essential for life
Formed by chromaffin cells, that are derived from neural crest cells
medulla comprises 10% of the mass of the adrenal gland

43
Q

Blood supply to adrenal gland

A

Suprarenal arteries
Form an arterial plexus on the surface of the adrenal gland
Sends 2 sets of arterioles into the gland:
Cortical arterioles and Medullary arterioles

44
Q

Cortical arterioles of adrenal gland

A

form fenestrated sinuses in the cortex

the sinuses drain into medullary sinuses

45
Q

glucocorticoids secreted by the cells of the cortex induce the conversion of

A

norepinephrine to epinephrine by the chromaffin cells of the adrenal medulla

46
Q

Medullary arterioles pass through

A

the cortex to supply the medulla

47
Q

Adrenal gland is drained by

A

a single suprarenal vein

48
Q

Nerve supply to adrenal gland

A

postganglionic sympathetic fibers to blood vessels of the cortex
preganglionic sympathetic fibers to medullary chromaffin cells

49
Q

Chromaffin cells

A

modified postganglionic sympathetic neurons

they release epinephrine and norepinephrine in response to impulses from preganglionic sympathetic fibers

50
Q

Adrenal Cortex- Zona Glomerulosa

A
  • thin layer of cells immediately deep to the capsule
  • the secretory cells form ovoid clumps
  • intensely staining spherical nuclei; little cytoplasm
  • SECRETE MINERALOCORTICOIDS (aldosterone and deoxycorticosterone) that function in the regulation of sodium and potassium homeostasis and water balance
  • cells are under control of the renin:angiotensin system
51
Q

renin:angiotensin system

A
  • low blood pressure or low blood sodium causes the release of renin from the JG cells of the kidney
  • circulating renin catalyzes the converstion of angiotensinogen to angiotensin 1
  • angiotensin 1 is converted to angiotensin 2 in the lungs by angiotensin converting enzyme (ACE)
52
Q

Angiotensin 2 stimulates

A

the cells of the zona glomerulosa to secrete aldosterone

53
Q

Adrenal Cortex- Zona Fasciculata

A
  • thick layer in the middle cortex
  • Large polyhedral cells in columns or cords
  • light staining spherical nuclei, often binucleate
  • steroid secreting cells that contain numerous lipid droplets
  • cytoplasm has a spongy appearance so the cells are sometimes called “foamy cells”
  • cords of the cells are separated by sinusoids
54
Q

Zona Fasciculata cells secrete

A

glucocorticoids (cortisone, corticosterone, cortisol) that regulate glucose and fatty acid metabolism and androgens (sex steroids)

hormone is released under control of ACTH

55
Q

Adrenal Cortex- Zona Reticularis

A

-Thin layer adjacent to the medulla
secretory cells form irregularly anastomosing cords, separated by sinusoids
-Smaller cells, deeply staining nuclei

56
Q

Zona Reticularis cells secrete

A

androgens and glucocorticoids

Hormone release is under control of ACTH

57
Q

Pathway that ACTH controls release of glucocorticoids and androgens

A

Corticotropic releasing hormone (CRH) is secreted by the hypothalamus–> it courses via the hypophyseal portal system to reach the pituitary corticotropes (in anterior pituitary)–> the corticotropes release ACTH–> ACTH stimulates the cells of the zona fasiculata and zona reticularis to secrete–> circulating levels of steroids influence release of CRH

58
Q

Medulla of adrenal gland

A

cells are in the form of cords, surrounded by blood vessels

59
Q

Secretory cells of medulla

A 
Chromaffin cells (large round cels) 
cells turn brown when reacted with chromium salts (hence the name) 
their cytoplasm is characterized by numerous granules
60
Q

Hormones released by Chromaffin cells

A

catecholamines, epinephrine and norepinephrine

Their action is sympathomimetic- increases heart rate, blood pressure, cardiac output, etc.
Aids organixm in stress situations
Hormones are released in response to nerve stimulation by preganglionic sympathetic fibers carried in the splanchnic nerves

61
Q

A tumor of the adrenal medulla is called a

A

pheochromocytoma

It results in hyperglycemia and intermittent high blood pressure

62
Q

Hyperactivity of the adrenal cortex results in

A

Conn’s syndrome- if it results in overproduction of aldosterone
Cushing syndrome- if it results in overproduction of glucocorticoids (more common)

63
Q

Cushing Syndrome is characterized by

A

wasting of the limbs and truncal obesity, a moon shaped face and development of a “buffalo hump” in the nuchal region
Purple striae are present over the abdomen and extremities
Hirsutism (hair growth in women) of the face and truck occurs

64
Q

Hypoactivity of the adrenal cortex causes

A

Addison disease
Usually results from autoimmune destruction of the adrenal cortex
It’s characterized by darkening of the skin and mucous membranes due to the increased production of melanin, decreased vigor, muscle strength and BP, and hair loss

Histology Exam 3 (7 decks)

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