Pituitary Histology and Physiology

Question 1

True or false: The pars distalis of the anterior pituitary has no direct arterial supply.

Answer 1

True

Question 2

What are the three cell types in the anterior pituitary and their relative proportions?

Answer 2

Acidophils (40-70%)
Chromophobes (50%)
Basophils (10%)

Question 3

Which two secretory cells of the anterior pituitary are acidophils?

Answer 3

Somatotropes and lactotropes

Question 4

Which two cell types secrete ACTH in the pituitary?

Answer 4

Corticotropes (pars distills)

Melanotropes (pars intermedia)

Question 5

What are two major products of melanotropes?

Answer 5

ACTH

Melanocyte-stimulating hormone (MSH)

Question 6

Basophils produce ____ hormones

Answer 6

Tropic hormones (i.e. hormones that act on other endocrine glands)

Question 7

What are two histological characteristics of the anterior pituitary?

Answer 7

Lots of rER (b/c produce PEPTIDE hormones)

Fenestrated capillaries

Question 8

Describe breakdown of POMC

Answer 8

1. y-MSH, ACTH, and B-lipotropin
2. ACTH -> a-MSH and CLIP
3. B-lipotropin -> y-lipotropin and B-endorphin
4. y-lipotropin -> b-MSH

Question 9

Why does Equine Pars Intermedia Dysfunction occur mostly in older horses?

Answer 9

Pars intermedia secretions are inhibited by dopamine, which declines with age

Question 10

Growth hormone is inhibited by

Answer 10

Somatostatin
Cortisol
Negative feedback (via IGF-1)

Question 11

Growth hormone is stimulated by

Answer 11

Ghrelin
T4
Androgens/Estrogen

Question 12

Which hormone controls growth at each life stage?

Answer 12

In utero - thyroid hormone
Postnatal - growth hormone/IGF-1
Puberty - sex hormones

Question 13

How do GH and IGF-1 affect bone growth differently?

Answer 13

GH - stimulates differentiation of prechondrocytes

IGF-1 - stimulates division of progenitor cells

Question 14

What are the 4 anti-insulin actions of GH?

Answer 14

1. Stimulates lipolysis/FFA in blood
2. Increases hepatic gluconeogenesis
3. Protects muscle protein
4. Enhances FFA oxidation by muscle

Question 15

What are growth promoting effects of GH?

Answer 15

1. Stimulates erythropoiesis
2. Enhances muscle maturation
3. Enhances skeletal maturation
4. Enhances milk production
5. Accelerates chondrogenesis
6. Increases calcium absorption

Question 16

Which factors promote prolactin secretion?

Answer 16

1. TRH

2. Estrogen/estradiol

Question 17

Which part of the hypothalamus produces ADH and oxytocin?

Answer 17

The cranial nuclei:

1. Paraventricular nucleus
2. Supraoptic nucleus

Question 18

Name three features of the hypothalamohypophyseal tract

Answer 18

1. Unmyelinated axons
2. End near capillaries (not neurons)
3. Neurosecretary vesicles clustered in Herring Bodies (hormones in Herring Bodies are bound to neurophysin)

Question 19

Glial cells in the pineal gland are called ______ whereas glial cells in the pars nervosa of the pituitary are called _____.

Answer 19

Pineal - astrocytes

Pituitary - pituicytes

Question 20

How do pituicytes appear in stained slides and EM?

Answer 20

Stained slides - oval/round nucleus, irregular branches, GFAP (+)

ER - big gap (“empty space”) between Herring Bodies (vesicles) and fenestrated capillaries

Question 21

Why is growth hormone diabetogenic?

Answer 21

It increases (hepatic) gluconeogensis AND inhibits insulin, which would normally promote glucose uptake into muscle