Male Reproductive Physiology

Question 1

what cells secrete Mullerian inhibiting factor? what is the function of MIF?

Answer 1

Sertoli cells; suppresses development of paramesonephric (Mullerian) ducts

Question 2

what cells secrete androgens? what is the function of androgens?

Answer 2

Leydig cells; stimulate development of mesonephric (Wolffian) ducts –> male phenotype

Question 3

what does the mesonephric duct develop into in the male fetus?

Answer 3

mnemonic: SEED

male internal structures (except prostate): Seminal vesicles, Epididymis, Ejaculatory duct, Ductus deferens

Question 4

what is the function of 5alpha-reductase?

Answer 4

converts testosterone to DHT (dihydrotestosterone)

Question 5

why do men have circulating estrogens?

Answer 5

expression of aromatase in peripheral (particularly adipose) tissue

Question 6

what enzyme converts testosterone to DHT (dihydrotestosterone) and why is this necessary?

Answer 6

5alpha-reductase; DHT has a higher affinity for androgen receptor in nucleus of target cells

Question 7

what two hormones are major stimulators of spermatogenesis?

Answer 7

FSH and local testosterone

Question 8

functions of testosterone (5)

Answer 8

1. differentiation of epididymis, vas deferens, seminal vesicles (genitalia, except prostate)
2. growth spurt: penis, seminal vesicles, sperm, muscle, RBCs
3. deepening of voice
4. closing of epiphyseal plates (via estrogen converted from testosterone)
5. libido

Question 9

where is inhibin made and what is its function?

Answer 9

Sertoli cell; inhibits only FSH release from anterior pituitary

Question 10

what hormone stimulates the Leydig cell and what is its main function?

Answer 10

LH; produces testosterone which has system androgenic effects and has local intra-testicular effects by diffusing into the Sertoli cell, increasing the response to FSH

Question 11

what hormone stimulates the Sertoli cell and what is its main function?

Answer 11

FSH; stimulates spermatogenesis and makes inhibin

Question 12

analogous cells in female and male gonads

Answer 12

leydig cell (testis) = theca interna cell (ovary)
Sertoli cell (testis) = granulosa cell (ovary)

Question 13

androgen-binding protein: where is it made, what is its function

Answer 13

Sertoli cell; acts as a local “sink” for testosterone so that developing sperm are bathed in very high concentrations of testosterone