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Histology > Lecture 14 - Thyroid, Parathyroid and Adrenal Glands > Flashcards

Lecture 14 - Thyroid, Parathyroid and Adrenal Glands Flashcards

1
Q

Thyroid structure and location

A

two lobes joined by an isthmus. Just below the larynx. anterior to the parathyroid.

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2
Q

Thyroid development

A

developed by the foramen cecum (same as tongue). will be in place after 7 weeks, below the larynx.

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3
Q

Colloid

A

gelatin like substance that fills the follicles of the thyroid. Is surrounded by follicular cells which secrete the colloid.

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4
Q

Follicular cells shape

A

typically squamos to columnar

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5
Q

Parafollicular cells (or C cells)

A

stain clearer. Produce calcitonin. can be embedded into the epithelium or can form bunches outside. Neural crest origin.

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6
Q

Vascularity of thyroid cells

A

frequent capillary openings with fenestrated endothelium.

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7
Q

Follicular cells contents

A

lots of RER, golgi, and microvilli

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8
Q

Thyroid hormones

A

T3 (triiodothryonine) and T4 (thyroxine), calcitonin.

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9
Q

T3 and T4

A

increase basal metabolic rate (T3 - mitochondrial number, cristae density and activity), influence body growth and nervous system development in the fetus. Stored in colloid. T4 most abundant. T3 most potent.

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10
Q

Calcitonin

A

produced and secreted by parafollicular cells or C cells. induced by increases in blood calcium levels, lowers blood calcium by inhibiting bone resorption (osteoclasts)

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11
Q

Iodine absorption in follicular cells

A

have iodide pumps (transporters) that concentrate iodide in the thyroid gland to make T3 and T4.

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12
Q

Thyroglobulin

A

glycoprotein that is synthesized by RER and secreted into the colloid.

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13
Q

Synthesis of thyroid hormones

A

Thyroglobulin produced, uptake of iodide by Na/I symporter on basolateral membrane, oxidation of iodine by thyroid peroxidase and transported into the follicle by pendrin, iodination by thyroid peroxidase occurs.

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14
Q

Pendrin

A

anion transporter to get oxidized iodine into the follicle

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15
Q

Thyroid peroxidase

A

oxidation of iodine in the cell and iodination of thyroglobulin in the follicle.

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16
Q

Thyroid feedback loop

A

hypothalamus releases TReleasingH which stimulates the anterior pituitary gland to release TSH (thyrotropin). TSH causes a release of T3/T4 into the blood stream and target cells. Feedback to the anterior pituitary and hypothalamus inhibit TRH.

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17
Q

Thyroid hormone secretion

A

upon stimulation of thyrotropin, follicular cells take up colloid by endocytosis. digested by lysosomal enzymes. Proteases free T3 and T4 to the cytoplasm and secreted basally into the blood. Rest is recycled.

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18
Q

T or F: Thyroid produces there products extracellularly

A

True.

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19
Q

Hyperactive thyroid follicle appearance

A

colloid is decreased. more of columnar epithelium.

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20
Q

Hypoactive thyroid follicle appearance

A

lots of colloid present. squamous epithelium since pushed by the colloid.

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21
Q

Parathyroid structure and location

A

4 small glands. posterior to thyroid.

22
Q

Parathyroid development

A

derived from the parapharyngeal pouches. Inferior come from 3rd pouch, superior come from 4th pouch.

23
Q

Two cell types of the parathyroid

A

chief (principal) cells and oxyphil cells

24
Q

Chief (principal) cells

A

produce parathyroid hormone which promotes bone reabsorption. dark staining. arranged in cords.

25
Q

Oxyphil cells

A

function is unknown, but abundance mitochondria. Light staining. accumulate in age, along with fat cells

26
Q

parathyroid hormone feedback loop

A

low blood calcium, stimulates parathyroid hormone secretion, PTH will cause bone to release calcium, kidneys to converse calcium, and intestine to increase absorption. Once calcium rises, PTH inhibited

27
Q

PTH 3 main targets

A

bone, kidney, and intestine

28
Q

PTH and bone

A

osteoblasts are the main target, which will produce osteoclast stimulating factor (paracrine mechanism) which induces the proliferation of osteoclasts - mobilizing calcium into the blood stream.

29
Q

PTH and kidney

A

kidneys conserve calcium in the tubule cells

30
Q

PTH and intestines

A

PTH induces the synthesis of vitamin D, which helps with the absorption of calcium.

31
Q

Adrenal structure and location

A

medulla, cortex, and capsule. two glands capping the kidneys but with no connection. Lots of adipose tissue but does not increase with age.

32
Q

Adrenal gland development

A

cortex - celomic epithelium (mesothelium) derived from mesoderm
medulla - neural crest cells derived from ectoderm

33
Q

3 layers of adrenal cortex

A

zona glomerulosa (15%), zona fasciculata (65%) with cords, and zona reticularis (7%)

34
Q

Zona glomerulosa

A

bent cords. interconnection between two segments. secrete mineralcorticoids.

35
Q

zona fasciculata

A

linear cord arrangement. Glucocorticoids and the androgens are secreted

36
Q

Zona reticularis

A

no specific cord arrangement. Lots of capillaries. also secrete glucocorticoids and androgens.

37
Q

Adrenal gland vascularization

A

highly vascularized. suprarenal vein in the medulla. arterial (via medullary arteries) and venous (via cortical veins) blood

38
Q

Aldosterone

A

(mineralcorticoid) secreted by columnar or pyramidal cells in the ZG. stimulates sodium reabsorption in the distal convoluted tubule of the kidney. Induced by angiotensin II.

39
Q

cortisol (hydrocortisone)

A

(glucocorticoid) secreted from ZF. increases blood sugar levels through gluconeogenesis. Suppress the immune system, and aid in fat, protein and carbohydrate metabolism.

40
Q

DHEA (dihydroepiandrosterone)

A

a weak androgen secreted by the ZR. converted into testosterone elsewhere in the body.

41
Q

Endocrine control of the ZF/ZR

A

hypothalamus is stimulated, induces ATCH from the anterior pituitary to the adrenal gland where it secretes glucocorticoids. Will feedback to hypothalamus and anterior pituitary

42
Q

Endocrine control of ZG

A

Aldosterone is controlled by angiotensin II (lung) which is derived from angiotensin I (kidney) which signal initially comes from the liver.

43
Q

Adrenal medulla

A

specialized postganglionic sympathetic neurons. produce epinephrine and norepinephrine

44
Q

Type of cells in the renal medulla

A

polyhedral parenchymal cells

45
Q

what is produced by medulla

A

epi, norepi, ATP, chromagranins, catecholamine-binding proteins, dopamine-B-hydroxylase, and enkephalins

46
Q

Staining of epinephrine and norepinephrine

A

epi: dark and regular/organized.
Noreip: very dark and irregular/disorganized.

47
Q

Fetal adrenal glands

A

much larger than in adults compared to body weight. secrete androgens and estrogens

48
Q

Short term response to stress of adrenal gland

A

epi and norepi released, heartbeat and blood pressure increase. blood glucose levels rise. muscles become energized.

49
Q

Long term response to stress of adrenal gland

A

glucocorticoids - protein and fat metabolism instead of glucose breakdown, reduction in inflammation, immune cells suppressed.
Mineralocorticoids - sodium ions and water are reabsorbed by kidney. blood volume and pressure increase.

50
Q

Hypophysectomy and the appearance of the adrenal cortex

A

removal of the hypothalamus causes cortical atrophy.

51
Q

Stress and appearance of the adrenal cortex

A

stress induces the hypothalamus and ACTH which causes thickening of the cortex.

Histology (20 decks)

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