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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
Hypothyroidism is
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
26
Children who are hypothyroid from birth, usually from non-development of a thyroid gland, have a condition called
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
Parathyroid gland
- 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
2 cell types of parathyroid gland
Chief (principal) cells | Oxyphil cells
29
The parathyroid gland is surrounded by
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
Blood supply to parathyroid gland
fenestrated capillaries from the thyroid arteries
31
Nerve supply to parathyroid gland
postganglionic sympathetic to blood vessels
32
Chief cells
presumptive hormone secretors vesicular (open faced) nucleus water clear (pale staining) cytoplasm
33
Oxyphil cell
``` 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
Hormone secreted by chief cells
parathyroid hormone (PTH)
35
Parathyroid hormone does what?
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
Parathyroid hormone release is directly controlled by
blood calcium levels | LOW levels stimulate secretion of PTH
37
Parathyroid glands are essential for life. Removal of the parathyroid gland (thyroidectomy) will result in
tetanic contraction of muscles due to the drop in blood calcium Contraction of the muscles related to respiration will cause death
38
Hyperparathyroidism is characterized by
increased blood calcium levels, resulting in pathologic deposits of calcium in organs such as the kidney and arteries
39
Hypoparathyroidism is characterized by
decreased blood calcium levels, with increased bone density | The decreased circulation of calcium levels cause skeletal muscles to undergo spastic contractions called tetany
40
Adrenal (Suprarenal) Gland
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
Adrenal Cortex
``` 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
Adrenal medulla
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
Blood supply to adrenal gland
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
Cortical arterioles of adrenal gland
form fenestrated sinuses in the cortex | the sinuses drain into medullary sinuses
45
glucocorticoids secreted by the cells of the cortex induce the conversion of
norepinephrine to epinephrine by the chromaffin cells of the adrenal medulla
46
Medullary arterioles pass through
the cortex to supply the medulla
47
Adrenal gland is drained by
a single suprarenal vein
48
Nerve supply to adrenal gland
postganglionic sympathetic fibers to blood vessels of the cortex preganglionic sympathetic fibers to medullary chromaffin cells
49
Chromaffin cells
modified postganglionic sympathetic neurons | they release epinephrine and norepinephrine in response to impulses from preganglionic sympathetic fibers
50
Adrenal Cortex- Zona Glomerulosa
- 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
renin:angiotensin system
- 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
Angiotensin 2 stimulates
the cells of the zona glomerulosa to secrete aldosterone
53
Adrenal Cortex- Zona Fasciculata
- 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
Zona Fasciculata cells secrete
glucocorticoids (cortisone, corticosterone, cortisol) that regulate glucose and fatty acid metabolism and androgens (sex steroids) hormone is released under control of ACTH
55
Adrenal Cortex- Zona Reticularis
-Thin layer adjacent to the medulla secretory cells form irregularly anastomosing cords, separated by sinusoids -Smaller cells, deeply staining nuclei
56
Zona Reticularis cells secrete
androgens and glucocorticoids | Hormone release is under control of ACTH
57
Pathway that ACTH controls release of glucocorticoids and androgens
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
Medulla of adrenal gland
cells are in the form of cords, surrounded by blood vessels
59
Secretory cells of medulla
``` Chromaffin cells (large round cels) cells turn brown when reacted with chromium salts (hence the name) their cytoplasm is characterized by numerous granules ```
60
Hormones released by Chromaffin cells
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
A tumor of the adrenal medulla is called a
pheochromocytoma | It results in hyperglycemia and intermittent high blood pressure
62
Hyperactivity of the adrenal cortex results in
Conn's syndrome- if it results in overproduction of aldosterone Cushing syndrome- if it results in overproduction of glucocorticoids (more common)
63
Cushing Syndrome is characterized by
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
Hypoactivity of the adrenal cortex causes
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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