Endocrine system

Question 1

Endocrine gland functions?

Answer 1

The functions include: regulation of growth, reproduction, metabolism, fluid levels, glandular secretion etc.

Question 2

How does the hypothalamus affect the endocrine system?

Answer 2

The hypothalamus is the site of release of the releasing and inhibiting factors that enter the hypothalamo-hypophyseal portal system and affect anterior pituitary function. It is also the site of neurons that manufacture oxytocin (paraventricular nucleus) and vasopressin (supraoptic nucleus) that send axons through the hypothalmo-hypophyseal tract to end in the posterior pituitary gland. These hormones are released into the blood stream, although they are not made in the posterior pituitary.

Question 3

What is the “master gland of the body”?

Answer 3

The pituitary gland controls many other endocrine glands

Question 4

What are the functions of oxytocin?

Answer 4

POSITIVE FEEDBACK LOOP on uterine smooth muscle during labor (will stimulate uterine contractions, and uterine contractions stimulate oxytocin release)

Contracts myoepithelial cells of mammary alveoli for milk letdown; which can be stimulated by suckling or by psychological factors (baby crying)

Question 5

What is the function of antidiuretic hormone?

Answer 5

ADH promotes water resorption from the collecting tubules & vasoconstriction

Question 6

What is the embyologic origin of the adenohypophysis?

Answer 6

The adeohypophysis (anterior pituitary) derives from Rathke’s Pouch

Question 7

What is the capillary organization of the anterior pituitary?

Answer 7

Many capillaries are part of the hypothalamo-hypophyseal portal system that takes releasing factors from the median eminence of the hypothalamus to the anterior pituitary. This system has many fenestrated capillaries and no barrier (such as the blood-brain barrier) in the hypothalamus or the anterior pituitary.

Question 8

What do acidophils of the adenohypophysis secrete?

Answer 8

Acidophils secrete growth hormone- somatotropes(GH; via growth hormone releasing hormone), and prolactin- mammotropes (PRL). These have direct effect on end-organs rather than on other endocrine organs.

Question 9

What does growth hormone do?

Answer 9

-Increases synthesis of growth factors
-Increases cell division, protein synthesis, lipolysis
-Regulates blood sugar:
low blood sugar-> GRH-> GH-> glycogen breakdown
High sugar–> Somatostatin-> Decreased GH- Less sugar breakdown

Question 10

What does Prolactin do?

Answer 10

Prolactin (PRL) promotes milk production. It is produced by lactotrophs and is normally inhibited by the hypothalamus via dopamine release into the hypothalamo-hypophyseal portal system. Suckling reduces this inhibition.

Question 11

What do basophils of the adenohypophysis do?

Answer 11

Basophils secrete ACTH (corticotropes), TSH (thyrotropes), and FSH, LH (gonadotropes).

Question 12

What do chromophobes of the adenohypophysis do?

Answer 12

Chromophobes are probably not active in secreting hormones. They may be resting or replacement cells.

Question 13

What does the thyroid gland control?

Answer 13

The thyroid gland controls metabolism, heat regulation, growth and nervous development.

Question 14

Describe the histologic appearance of the thyroid

Answer 14

The thyroid is characterized by large follicles lined by cuboidal follicular cells. There is colloid within the follicles (more in inactive glands) and there are parafollicular “C” cells between the follicles. As with all endocrine glands, there are many capillaries.

Question 15

What is colloid?

Answer 15

Colloid made of the protein thyroglobulin. This is secreted into follicle by the follicular cells. These cells take up iodine and pump it into the follicle where it iodinates thyroglobulin to make T3 and T4.

Question 16

How is thyroid hormone secreted?

Answer 16

Under the influence of TSH, follicular cells reuptake thyroglobulin and liberate T3 & T4. This is secreted into the blood stream.

Question 17

What is the significance of resorption lacunae? Where are they most prominent?

Answer 17

Resorption lacunae are the regions near the active follicular cells where processes of these cells have internalized thyroglobulin, leaving an empty-appearing region adjacent to the cell. These are more prominent in an active thryroid.

Question 18

What do parafollicular (C) cells do?

Answer 18

C cells make calcitonin, which decreases Calcium in blood by several mechanisms, including decreasing intestinal absorption and renal tubular resorption of calcium and by inhibiting osteoclasts in the bone.

Question 19

Why is calcium regulation important?

Answer 19

Hypocalcemia results in muscle cramps and muscle tetany. Hypercalcemia results in muscle weakness and can produce confusion and stupor

Question 20

Where are the parathyroid glands?

Answer 20

There are usually 4 of them on the back of the thyroid gland. However, the location is variable.

Question 21

What kind of cells are in the parathyroid glands?

Answer 21

Chief cells secrete PTH (parathyroid hormone). Oxyphil cells are more eosinophilic, partially due to lots of mitochondria. These cells have no known function.

Question 22

What are the layers of the adrenal cortex?

Answer 22

The layers of the adrenal cortex (from superficial to deep) are the zona glomerulosa, the zona fasciculate and the zona reticularis.

Question 23

What does the zona glomerulosa do?

Answer 23

The zona glomerulosa cells secrete mineralocorticoids (aldosterone), which helps regulate electrolyte and water levels. The hormone is under the influence of the renin-angiotensin system.

Question 24

What does the zona fasciculata do?

Answer 24

The zona fasiculata cells secrete glucocorticoids (cortisol). This is a hormone that helps the body deal with stressful situations. It increases blood sugar, fat, amino acids, and blood pressure. It has a circadian rhythm, being high in the morning. This is regulated by ACTH from the adenohypophysis.

Question 25

What does the Zona Reticularis do?

Answer 25

The zona reticularis secretes androgens. It has little effect in males, but is responsible for testosterone in women and makes estrogen in postmenopausal women.

Question 26

What are the cells of the adrenal medulla called and what do they do?

Answer 26

The cells of the adrenal medulla are called chromaffin cells. They are innervated by sympathetics preganglionic neurons and secrete epinephrine and some norepinephrine. These hormones will increase blood pressure, heart rate and blood glucose.

Question 27

What is the endocrine portion of the pancreas called?

Answer 27

The endocrine portion of the pancreas is called the pancreatic islets of Langerhans.

Question 28

What types of cells are in the endocrine pancreas and what do they do?

Answer 28

Beta cells: Insulin (gets glucose into cells to lower blood sugar)
Alpha: Glucagon (Breaks glucose down-> raises blood sugar
Delta: Somatostatin (inhibits local hormone production)
F-cells (Pancreatic polypeptide: unknown function)

Question 29

What are the cells of the pineal gland called and what are the distinctive histologic features

Answer 29

The functional cells of the pineal gland are pinealocytes. Corpora arenacea (mineral deposits that show up on CT/MRI) are the most distinctive feature.

Question 30

What does the pineal gland do?

Answer 30

This gland produces melatonin (important in the circadian clock).