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FoundSci Unit 6 > Endocrine Glands II > Flashcards

Endocrine Glands II Flashcards

1
Q

What is the structure of the thyroid gland?

A

Sits anterior to trachea in neck - 2 lobes connected by the isthmus

CT capsule send extensions (septa) inward - subdivide the thyroid lobes into lobules

Each lobule contains follicles

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2
Q

What is the histology of thyroid gland?

A

Parenchyma - thyroid follicles which contain endocrine cells (follicular cells) and contains colloid

Areas between follicles are fenestrated capillaries and endocrine cells called parafollicular cells

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3
Q

What is the basic structural unit of the thyroid gland?

A

Follicles

Walls are simple cuboidal epithelium and these cells are follicular cells

Contents are colloid

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4
Q

What is the structure and function of follicular cells?

A

Form the follicle wall and synthesize the thyroid hormones T3 and T4

T3 and T4 increase metbaolic rate and influence body growth and development

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5
Q

What is colloid?

A

Thyroglobulin

Storage form of T3 and T4 hormones

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6
Q

What is the areas between thyroid follicles?

A

Fenestrated capillaries

Parafollicular cells (clear cells and C cells) - they synthesize calcitonin and release it when blood calcium levels are high

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7
Q

What does calcitonin do and what is it released?

A

Inhibits osteoclast activity so there is less bone resorption and lowers calcium in blood

released by parafollicular cells

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8
Q

What are the parathyroid glands?

A

4 small glands embedded in CT capsule of thyroid gland

Each gland has a CT capsule that sends short extensions (septa) inward

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9
Q

What are the main cells of the parathyroid glands?

A

Endocrine cells - cheif cells

Oxyphil cells - function unknown

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10
Q

What is the structure and function of chief cells?

A

Smaller cells, basophilic cytoplasm

Synthesize, store, and release parathyroid hormone (PTH, parathormone)

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11
Q

What does PTH do?

A

Stimulates osteoclast activity which means more bone resorption and raises calcium in blood

Also causes a decrease in kidney calcium excretion by stimulating calcium reabsorption

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12
Q

What is the structure and function of oxyphils?

A

Function is unknown

Larger cells, acidophilic cytoplasm and isolated in clusters

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13
Q

Do PTH and calcitonin have the same or opposite effects?

A

Opposite!

PTH - chief cells of parathyroid

Calcitonin - parafollicular cells of thyroid gland

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14
Q

What is the structure of the suprarenal gland?

A

Lies in fat lobule atop kidney

Dual embryonic origin - cortex from mesoderm and medulla from neural crest (ectoderm)

CT capsule sends longer extensions (trabeculae) deep inward

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15
Q

What do the trabeculae of the suprarenal gland do?

A

Anchor the capsule in deeper tissues

Pathways for vessels and nerves that supply the gland

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16
Q

What is the parenchyma of the suprarenal gland?

A

Cortex with 3 distinct zones - zona glomerulosa, zona fasciculata, and zona reticularis

Medulla has endocrine cells called chromaffin cells

17
Q

What do all endocrine cells in cortex synthesize?

A

Corticosteroids (from cholesterol)

Syntehtic activity regulated by anterior pituitary

Cells in each zone form clusters that are separate by fenestrated capillaries

18
Q

What is the zona glomerulosa and what is its function?

A

Outer zone of cortex

Cells synthesize 2 mineralocorticoids:

Aldosterone - regulates water and electrolyte balance by stimulating sodium absorption and potassium excretion in the distal convoluted tubules of the kidneys

Deoxycorticosterone - promotes sodium absorption

19
Q

What is the zona fasciculata and its function?

A

Middle and largest zone of the cortex

Cells are spongiocytes that contain numerous lipid droplets

Cells synthesize 2 glucocorticoids that regulate carbohydrate, protein, and fat metabolism - cortisol and corticosterone

20
Q

What are the effects of cortisol? A BIG FIB

A

Increase
Appetite
Blood pressure
Insulin resistance
Gluconeogenesis while decreasing glucose utilization

Decrease
Fibroblast activity (decrease collagen and elastin synthesis and slows healing)
Inflammatory and immune system responses
Bone formation (decrease osteoblast activity)

21
Q

How is cortisol stimulated to be released?

A

CRH from hypothalamus stimulates corticotrophs to make and release ACTH

ACTH stimulates spongiocytes to make and release cortisol

Excess cortisol suppresses release of CRH, ACTH, and cortisol

22
Q

What is the structure and function of the zona reticularis?

A

Inner zone of cortex with strongly acidophilic cells

The cells synthesize 2 weak androgens:
Dehydroepiandrosterone (DHEA) and androstenedione

These hormones have masculinizing effects in males and females but the effect is weaker in males

Cells also synthesize small amounts of glucocorticoids

23
Q

What are the cells and functions of the suprarenal medulla?

A

Chromaffin cells that synthesize 2 catecholamine that synthesize epinephrine (adrenaline) and norepinephrine (noradrenaline)

Medulla also has sympathetic ganglion cells whose axons innervate smooth muscle cells in cortical blood vessels and also modules cortical activity

24
Q

What is the pineal gland and its functions?

A

Neuroendocrine organ - neurons secrete hormones that regulate day/night cycles

Each pineal gland has a CT capsule that send septa inward. Septa mainly serve as pathways for the vessels and nerves that supply the gland

25
Q

What is in the parenchyma of the pineal gland?

A

Endocrine cells - pinealocytes

Neuroglial cells

Pineal sand

26
Q

What is the function of the pinealocytes?

A

Receive info about current light levels and synthesize 2 hormones that regulate circadian rhythms

Convert tryptophan into serotonin, which is converted into melatonin

Melatonin synthesize is organelles called synaptic ribbons

27
Q

What is the function of neuroglial cells of pineal gland?

A

Functions are similar to those of astrocytes and microglia

28
Q

What is the function of pineal sand?

A

Calcified concretions

Function unknown

29
Q

What are the dual glands of the pancreas? What is the other part of its structure?

A

Exocrine pancreas - serous acini that secrete digestive enzymes

Endocrine pancreas - pancreatic islets (islets of Langerhans)

CT capsule sends septa inward that subdivide lobes into smaller lobules. Septa forms paths for vessels and nerves that supply the gland and forms path for larger ducts carrying exocrine secretions

30
Q

What is part of the stroma and the parenchyma of the endocrine pancreas?

A

Stroma: Capsule and septa (dense irregular CT), Internal scaffold (reticular fibers)

Each islet surrounded by reticular fibers

Parenchyma - islets. contains fenestrated capillaries

31
Q

What are the pancreatic islet cells?

A

Alpha cells

Beta cells

Delta cells - D and D1

Epsilon cells

PP cells (F cells)

Gastrin producing cells (G cells)

32
Q

What do alpha cells secrete and synthesize?

A

Glucagon which increases blood glucose levels

33
Q

What do beta cells secrete and synthesize?

A

Insulin - lowers blood glucose levels

Amylin - inhibits stomach emptying and glucagon release

34
Q

What do delta cells secrete and synthesize?

A

D cells - somatostatin which reduces smooth muscle contraction in the GI tract and gallbladder after a meal

D1 cells - vasoactive intestinal peptide - induces glycogenolysis and modulates smooth muscle contraction in the GI tract

35
Q

What do epsilon cells secrete and synthesize?

A

Ghrelin - induces the sensation of hunger

36
Q

What do PP cells secrete and synthesize?

A

Pancreatic polypeptide which inhibits the secretion of digestive enzymes by the pancreas

37
Q

What do gastrin producing cells secrete and synthesize?

A

Gastrin - stimulates parietal cells in mucosa layer of stomach wall to synthesize and release HCl

FoundSci Unit 6 (14 decks)

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