Endocrine II - Thyroid, Parathyroid, and Adrenal Glands Flashcards

1
Q

What is the thyroid gland derived from?

A

A downgrowth of oral epithelium from the base of the tongue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What type of cells line thyroid lobules?

A

Follicular cells are simple cuboidal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are thyroid follicle lumens filled with?

A

Colloid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is colloid made from?

A

Thyroglobulin - a precursor of thyroid hormone.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the basic steps in thyroid hormone synthesis?

A
  1. Thyroglobulin is made by follicular cell and exocytosed into colloid
  2. Conjugation in the colloid produces triiodothyronine and tetraiodothyronine residues bound to thyroglobulin
  3. Cell endocytoses colloid, bringing in the hormone precursors.
  4. Endosomal acidification results in proteolytic cleavage, releasing T3 and T4.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Which thyroid hormone is most potent?

A

T3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Where are parafollicular cells found? What do they do?

A

They are found deep to the follicular epithelium of the thyroid lobules and they secrete calcitonin.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What does calcitonin do?

A

Lowers blood calcium levels by lowering osteoclast activity and lowering calcium absorption.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How do parafollicular cells stain?

A

Pale-staining. Calcitonin granules can be seen with EM.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Where are the parathyroid glands located?

A

Posterior surface of the thyroid.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What two cell types are found in the parathyroid gland? Which one is most abundant?

A

Chief cells and oxyphil cells. Chief cells most abundant.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What do chief cells of the parathyroid do?

A

Produce parathyroid hormone (PTH)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is a histological feature of parathyroid chief cells?

A

Dark, centrally-located nuclei, small cytoplasm, tightly packed together.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What does parathyroid hormone (PTH) do?

A

Raises calcium levels by increasing osteoclast activity and stimulating vitamin D activation in the kidney. Vitamin D increases calcium absorption in the GI tract.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

PTH and calcitonin are antagonists to each other, but only one is essential. Which one is it?

A

PTH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What do parathyroid oxyphil cells look like histologically?

A

Pale, large cytoplasm surrounding dark, centrally-located nuclei. They look like fried eggs. They exist in clumps.

17
Q

Where are the adrenal glands located?

A

Superior to the kidneys.

18
Q

What structure surrounds the adrenal glands?

A

A thick CT capsule (with trabeculae)

19
Q

What is the main function of the adrenal cortex?

A

Steroid hormone production

20
Q

What is the main function of the adrenal medulla?

A

Catecholamine production

21
Q

What are catecholamines derived from?

A

Tyrosine

22
Q

What controls the adrenal cortex?

A

Angiotensin II and ACTH

23
Q

What is the adrenal medulla controlled by?

A

Sympathetic fibers and adrenal cortex hormones

24
Q

What are the three zones of the adrenal cortex?

A

Outer: Zona glomerulosa, middle: zona fasciculata, inner: zona reticularis

25
Q

What do zona glomerulosa cells do? How are they arranged?

A

They make mineralocorticoids like aldosterone. Cells are found in clumps.

Note: Mineralocorticoids are so named because they are steroid hormones that regulate salt balance (mineral balance).

26
Q

Which adrenal cortex zone is the widest?

A

Zona fasciculata

27
Q

What is produced in the zona fasciculata?

A

Glucocorticoids like cortisol and sex steroids.

Note: Glucocorticoids are steroid hornomes that regulate carbohydrate metabolism.

28
Q

What is made in the zona reticularis?

A

Androgens mainly

29
Q

What is the main cell type found in the adrenal medulla?

A

Chromaffin cells.

30
Q

What are chromaffin cells derived from?

A

Neural crest

31
Q

What are the two types of chromaffin cells?

A

E cells and NE cells.

32
Q

What do E cells and NE cells do?

A

E cells make, store, and release epinephrine.

NE cells make, store and release norepinephrine.

33
Q

What is special about the blood supply in the adrenal gland?

A

Some arteries feed the cortex first, then re-join to go to the medulla. This allows glucocorticoids made in the cortex to exert their effects on the medulla.

34
Q

What controls the zona glomerulosa? What controls the zona fasciculata?

A

Angiotensin II controls glomerulosa. ACTH controls the fasciculata.

35
Q

What is the adrenal medulla derived from?

A

Neural crest.