Male Reproductive Physiology

Question 1

Determination of male phenotype

Answer 1

Testosterone stimulates growth and differentiation of wolffian duct
Antimullerian hormone causes atrophy of mullerian ducts

Question 2

How is testicular temp maintained?

Answer 2

Countercurrent arrangement of arteries and veins

Question 3

Cells of testes and function

Answer 3

Seminiferous tubules – make sperm
Sertoli cells – provide nutrients for sperm, make up blood-testes barrier, make fluid to help transport sperm, make inhibin and antimullerian hormone
Leydig cells – make testosterone

Question 4

Spermatogenesis pathway

Answer 4

Spermatogonia –> diploid spermatocytes –> haploid spermatocytes –> spermatids –> spermatozoa (sperm cell)
Takes 64 days

Question 5

Pathway of sperm

Answer 5

Seminiferous tubules –> Epididymis –> Vas deferens –> Ejaculatory duct –> Urethra –> Penis

Question 6

Purpose of vas deferens

Answer 6

storage of sperm in ampulla

secretes citrate and fructose fluid

Question 7

Purpose of seminal vessicles

Answer 7

Make fluid w/ citrate, fructose, prostaglandins for sperm

Question 8

Purpose of prostaglandins in semen

Answer 8

Make cervical mucus more penetrable

Induce uterine contractions to help propel sperm

Question 9

Purpose of prostate gland

Answer 9

Creates alkaline milky solution of citrate and calcium for semen

Question 10

What is capacitation? Why does it happen?

Answer 10

4-6 hr period while sperm are in female reproductive tract to wash inhibitory factors out and cause acrosomal rxn

Question 11

Purpose of acrosome

Answer 11

Contains proteolytic enzymes to penetrate egg

Question 12

Synthesis of testosterone

Answer 12

LH stimulates cholesterol desmolase in Leydig cells –> production of androstenedione –> converted to testosterone via 17B hydroxysteroid dehydrogenase

Question 13

How is testosterone handled in circulation?

Answer 13

98% bound to sex steroid binding globulin

Question 14

Activity of GnRH

Answer 14

Pulsatile release (triggered at puberty) –> travels thru hypophyseal portal to anterior pituitary –> triggers pulsatile release of FSH/LH

Question 15

Activity of FSH

Answer 15

Stimulates spermatogenesis in germ cells and Sertoli cell function

Question 16

Activity of LH

Answer 16

Stimulates testosterone production via activation of cholesterol desmolase

Question 17

Negative feedback mechanisms

Answer 17

Testosterone decreases frequency and amplitude of GnRH secretion
Inhibin produced by Sertoli cells inhibits FSH secretion at anterior pituitary

Question 18

Actions of testosterone

Answer 18

Differentiation of internal male genitalia 
Increased muscle mass
Increased linear growth
Closure of epiphyseal plates
Growth of penis and seminal vesicles
Local stimulation of spermatogenesis 
Deepening of voice
Libido

Question 19

Conversion of testosterone

Answer 19

Converted to dihydrotestosterone via 5a-reductase

Question 20

Actions of dihydrotestosterone

Answer 20

Differentiation of external male genitalia
Growth of prostate
Male hair distribution

Question 21

How does testosterone/DHT act on target cells?

Answer 21

Binds to intracellular receptor –> complex translocates to nucleus – initiates gene transcription