11: Male Reproductive Physio

Question 1

Genetic sex in embryos week 5, 6, ad 9

Answer 1

Week 5: gonads are bipotential
Week 6: testes begin to form in males
Week 9: ovaries begin to form in females

Question 2

What determines phenotypic sex?

Answer 2

Hormonal output of gonads

Question 3

What initiates puberty?

Answer 3

Pulsatile secretion of GnRH causing a pulsatile secretion of FSH and LH to stimulate gonadal steroid hormones

Question 4

Regulating puberty: GnRH analogue in pulses vs long-acting

Answer 4

GnRH analogue in pulses: puberty is initiated, reproductive function is established
GnRH long-acting: puberty is not initiated

Question 5

P450scc

Answer 5

Aka desmolase, cholesterol -> pregnenolone

Question 6

Three androgens secreted by testes

Answer 6

T, DHT, androstenedione

Question 7

Most abundant androgen secreted by testes

Answer 7

Testosterone

Question 8

End product of steroid synthesis in testes vs adrenal gland

Answer 8

Testes: T
Adrenals: DHEA and androstenedione

Question 9

Two enzymes lacking in the testes and the outcome of this

Answer 9

Lacks: 21B-hydroxylase & 11B-hydroxylase -> no mineralocorticoids or glucocorticoids

Question 10

Three big androgenic actions of androgens

Answer 10

1. Differentiation of male internal and external genitalia in fetus
2. Stimulate secondary sexual characteristics at puberty
3. Maintain reproductive tract and production of semen and sperm

Question 11

7 Anabolic actions of androgens

Answer 11

1. Erythropoeitin synthesis
2. ABP synthesis
3. Control protein anabolic effects (N retention)
4. Maintain sex gland secretions
5. Sebaceous gland secretions
6. Regulate behavior
7. Regulate libido

Question 12

Three forms of circulating T

Answer 12

1. 60% bound to SHBG
2. 38% bound to albumin
3. 2% free (most important biologically)

Question 13

What will not occur without FSH?

Answer 13

Spermiogenesis

Question 14

What happens with no GH?

Answer 14

Spermatogenesis is severely deficient or absent -> pt is infertile

Question 15

Sperm maturation in epididymis

Answer 15

Spend about 1 month (can spend several) in epididymis becoming more mature and becoming strongly motile

Question 16

Decapacitation in epididymis

Answer 16

Adding moleucles to sperm membrane to prevent acrosomal reaction before contact with egg

Question 17

Final pH of semen

Answer 17

7.5

Question 18

Lifespan of sperm once ejaculated

Answer 18

24-48 hours at body temp

Question 19

Ml of semen per ejaculate

Answer 19

2-6ml

Question 20

Sperm count to be considered infertile

Answer 20

Less than 20 million

Question 21

Two differences between male and female tracts

Answer 21

1. Males have continuous lumen from seminiferous tubule to end of male tract
2. Male tract connects to distal urinary tract

Question 22

Helicine arteries

Answer 22

Supply blood to cavernous spaces of penis

Question 23

Pathway for erection

Answer 23

1. Parasymp nerves stimulate helicine arteries
2. NO released -> guanylate cyclase -> increased cGMP -> vasodilation
3. Blood flows into spaces -> erection

Question 24

How erection is maintained

Answer 24

Engorged tissues press dorsal veins against outer fascia (tunica albuginea) -> reduced drainage

Question 25

How does somatic stimulation help maintain erection?

Answer 25

Increased contraction of muscles at base of penis -> further promote erection

Question 26

Emission of sperm control

Answer 26

Sympathetic

Question 27

Internal sphincter of bladder

Answer 27

Closed during emission to prevent retrograde ejaculation into bladder

Question 28

Process that causes ejaculation

Answer 28

1. Rhythmic contraction of bulbospongiosus + ischiocavernosus innervated by somatic motor nerves

Question 29

Why penis becomes flaccid after ejaculation

Answer 29

Sympathetics constrict helicine arteries -> decreased blood flow -> veins drain most of the blood

Question 30

What enzyme converts androstenedione to testosterone?

Answer 30

17B-hydroxysteroid dehydrogenase

Question 31

What does aromatase do?

Answer 31

Testosterone -> estradiol