Male Reproductive Physiology

Question 1

Puberty is initiated by pulsatile secretion of ___, which drives the pulsatile secretion of ___.

Answer 1

GnRH

FSH, LH

Question 2

What structure is the primary location for maturation and location of sperm?

Answer 2

Epididymis

Question 3

What is the function of the Leydig cells?

Answer 3

Synthesis and secretion of testosterone

Question 4

Unlike other hormone-producing organs, what enzymes do the testes lack? What is the result?

Answer 4

21B-hydroxylase and 11B-Hydroxylase

No glucocorticoids or mineralocorticoids

Question 5

What enzyme converts androstenedione to testosterone?

Answer 5

17B-hydroxysteroid dehydrogenase

Question 6

How is testosterone concentrated in the lumen of the seminiferous tubules?

Answer 6

Testosterone is bound to androgen-binding protein

Question 7

What is the enzyme that converts T to DHT?

Answer 7

5a-reductase

Question 8

What binds most of the circulating testosterone?

Answer 8

Sex hormone-binding globulin (SHBG) and albumin

Question 9

What is the source of estrogen in the fluid of seminiferous tubules?

Answer 9

Sertoli cells

Question 10

What is the rate-limiting step in the synthesis of testosterone?

Answer 10

Conversion of cholesterol to pregnenolone

Question 11

What 2 ways does LH promote pregnenolone synthesis?

Answer 11

Increase affinity for P450scc enzyme (desmolase) for cholesterol

Stimulate synthesis of P450scc enzyme

Question 12

In what weeks of gestation does testosterone production begin?

Answer 12

Weeks 7-8

Question 13

Where are androgen receptors found in the male reproductive system?

Answer 13

Prostate, testes, epididymis, seminal vesicles

Question 14

Where are androgen receptors found in the female reporductive system?

Answer 14

Ovary, mammary glands, uterus

Question 15

What is the primary mode of excretion of testosterone and its metabolites?

Answer 15

Through urine as urinary 17-Ketosteroids

Question 16

What will a deficiency of testosterone in the 3rd trimester of pregnancy cause in a male fetus?

Answer 16

Cryptorchidism - lack of descent of testes into scrotum

Micropenis

Question 17

What would you use to treat male pattern baldness and benign prostatic hypertrophy?

Answer 17

5a-reductase inhibitors to lower the concentration of DHT in the body

Question 18

What are the anabolic actions of androgens? (There’s a lot.)

Answer 18

Stimulation of erythropoietin synthesis

Stimulation of sebaceous gland secretion

Control of protein anabolic effects (nitrogen retention)

Stimulation of linear body growth, bone growth, and closure of epiphyses

Stimulation of ABP synthesis

Maintenance of secretions of sex glands

Regulation of behavioral effects, including libido

Question 19

Is BPH resultant of DHT concentration or receptor disorder?

Answer 19

Receptor, pt’s with BPH may have more DHT receptors

Concentration of DHT is not abnormal

Question 20

What is the action of Inhibin B?

Answer 20

Released by sertoli cell to block FSH release from anterior pituitary

Question 21

How long does spermatogenesis take?

Answer 21

64 days

Question 22

What is the role of growth hormone in spermatogenesis?

Answer 22

Promotes early division of sperm

Controls background metabolic fxns of testes

Question 23

What is the eventual effect of exogenous testosterone on spermatogenesis?

Answer 23

Insufficient spermatogenesis because hypothalamus is inhibited from producing GnRH which activates the whole pathway

Question 24

Where does decapacitation occur? What does it involve?

Answer 24

Epididymis

Add molecules to membrane of sperm to prevent acrosomal rxn before contact with an egg

Question 25

What is the function of prostaglandins in the semen?

Answer 25

React with cervical mucus to make it more receptive to sperm movement

Cause backwards, reverse peristaltic contractions in uterus and fallopian tubes to move sperm towards ovaries

Question 26

In the male sexual response, emission is controlled by what autonomic division?

Answer 26

Sympathetic, adrenergic transmitter

Causes peristaltic contraction of SM of vas deferens, closing internal sphincter of bladder

Question 27

Contraction of what muscles are responsible for the ejaculation phase of the male sexual response?

Answer 27

BUlbospongiosus and ischiocavernosus ms.

Question 28

Where does capacitation occur? What does it involve?

Answer 28

Vagina

Loss of cholesterol and inhibitory factors on head of the sperm, increased motility due to increased permeability to Ca2+

Question 29

What occurs during the sperm acrosome reaction?

Answer 29

Hyaluronidase and proteolytic enzymes released from the head of the sperm depolymerize the polymers holding the granulosa cells together and “eat” through zona pellucida, creating passageway for sperm

Question 30

What would a testosterone deficiency cause in the 2nd-3rd month of gestation in a male fetus?

Answer 30

Ambiguous male genitalia

Male pseudohermaphrodism/Intersex/DSD

Question 31

What would testosterone deficiency cause in a young male going through puberty?

Answer 31

Poor secondary sex development

Eunuchoidism - persistent prepubertal characteristics/characteristics of females

Question 32

What would testosterone deficiency cause in a post-pubertal male?

Answer 32

Decreased libido, ED

Decreased facial and body hair

Low energy

Infertility

Question 33

What causes Kallman’s syndrome?

Answer 33

Failure of GnRH neurons to migrate into hypothalamus during embryonic development

Question 34

What disorder is characterized by delayed or absent puberty and impaired sense of smell?

Answer 34

Kallman’s syndrome, secondary hypogonadism (hypogonadotropic hypogonadism)

Question 35

What are the characteristics of Klinefelter syndrome?

Answer 35

Extra X

During puberty, increased gonadotropins fail induce normal testicular growth and spermatogenesis

Low androgen production (primary hypogonadism)

Largely destroyed seminiferous tubules => infertility

Question 36

As men age, what happens to gonadal sensitivity to LH? What is the result?

Answer 36

Decreases

Increased serum FSH >LH