Lecture 25: Male Reproductive Physiology

Question 1

The pulsatile secretion of what hormone initiates puberty?

Answer 1

GnRH

Question 2

GnRH drives the pulsatile secretion of what hormones?

What are these hormones responsible for?

Answer 2

FSH and LH

-secondary sex characteristics

Question 3

During the adult reproductive period, is LH or FSH secreted more?

Answer 3

LH

Question 4

What is the function of the testes?

Answer 4

1) Spermatogenesis

2) Testosterone secretion

Question 5

What is the function of the epididymis?

Answer 5

Primary location for maturation and storage of sperm

Question 6

What is the function of the vas deferens?

Answer 6

• Storage for sperm

- Secrete rich fluid

Question 7

What is the function of the sminal vesicle?

Answer 7

Secretes fluid that aids in the motility of sperm and penetration –> becomes semen

• prostaglandins helps semen react with female cervix
• helps ejaculated sperm into fallopian tube and uterus

Question 8

What is the function of the prostate gland?

Answer 8

Secrete solution that gives the semen an alkaline pH to survive in the acidity in female vagina

Question 9

What two type of cells are found in the seminiferous tubules?
What are their functions?

Answer 9

Sertoli cells: produce sperm and forms barrier between testes and bloodstream
Leydig cells: produce testosterone

Question 10

Where are spermatogonia and spermatozoa found?

Answer 10

Spermatogonia (immature sperm): periphery

Spermatozoa (mature sperm): lumen of tubule

Question 11

In the lumen of the seminiferous tubules, how is testosterone concentrated?

Answer 11

Testosterone is bound to androgen-binding protein (ABP)

-ABP secreted by sertoli cells

Question 12

What converts androstenedione to testosterone?

Answer 12

17β-hydroxysteroid dehydrogenase

Question 13

What converts testosterone to dihydrotestosterone?

Answer 13

5α-reductase

Question 14

In circulation, what is testosterone bound to?

Answer 14

Sex hormone binding globulin (SHBG)

Question 15

What is the first step in testosterone production?

Answer 15

Cholesterol –> Pregnenolone

-RATE LIMITING STEP

Question 16

Where is estrogen produced in the males?

Answer 16

1) Sertoli Cells:
Testosterone –> Estradiol via aromatase

2) Liver

Question 17

What stimulates the conversion of cholesterol into pregnenolone?

Answer 17

LH

• Leydig cells has receptor for LH
• increased affinity of P450scc enzyme

Question 18

The androgen receptor complex is a ____ receptor.

Answer 18

Nuclear receptor

Question 19

What might happen if there is a deficiency of 5α-reductase?

Answer 19

Lack of dihydrotestosterone (DHT)

-ambiguous external genitalia

Question 20

What is cryptorchidism?

Answer 20

Lack of descent of testes

Question 21

What is testosterone responsible for?

Answer 21

• Increased muscle mass
• Pubertal growth spurt
• Closure of the epiphyseal plates
• Growth of the penis & seminal vesicles
• Deepening of the voice
• Spermatogenesis
• Libido

Question 22

What is DHT responsible for?

Answer 22

• External male genitalia
• Male hair distribution
• Sebaceous gland activity
• Growth of prostate

Question 23

What is benign prostatic hyperplasia?

Answer 23

Prostate gland enlargement

-more DHT receptors

Question 24

What stimulates Sertoli cells?

Answer 24

Testosterone and FSH

-secretes ABP into seminiferous tubules (increase testosterone concentration)

Question 25

What inhibits Sertoli cells?

Answer 25

Inhibin which inhibits FSH

Question 26

Describe the process of spermatogenesis.

Answer 26

Phase 1: Mitotic divisions
-results in primary spermatocytes (diploid 4N)

Phase 2: Meiotic divisions

• Secondary spermatocytes (haploid 2N)
• Spermatids (haploid 1N)

Phase 3: Spermiogenesis
-spermatids mature into spermatozoa

Question 27

What hormones stimulate spermatogenesis?

Answer 27

LH: stimulate secondary spermatocyte 
FSH: stimulate primary spermatocyte
GH
Testosterone
Estrogen

Question 28

In the epididymis, how does the sperm mature?

Answer 28

• Becomes more motile
• Decapacitation to prevent acrosomal reaction before contact egg
• Will spend a month

Question 29

What is the function of the bulbourethral gland?

Answer 29

Located beneath the prostate gland at the beginning of the internal portion of the penis;

• add fluids to semen during the process of ejaculation
• alkaline fluid to neutralize any mild acidity

Question 30

What three erectile bodies make up the penis?

Answer 30

2 corpus cavernosa

1 corpus spongiosum

Question 31

During an erection, what do the parasympathetic nerves stimulate?

Answer 31

Innervate vascular smooth muscle of helicine arteries

• NO released –> relaxation of smooth muscle
• penis is engorged and erect
• somatic stimulation increases contraction of muscle

Question 32

During an erection, what does the sympathetic control do?

Answer 32

Movement of semen from epididymis to ejaculatory duct

-closing internal sphincter of bladder

Question 33

What causes ejaculation?

Answer 33

Rhythmic contraction of bulbospongiosus and ischiocavernosus muscles at base of penis
-innervated by somatic motor nerves

Question 34

When sperm enters the female tract, what happens to the sperm?

Answer 34

Capacitation of sperm

• loss of inhibitory factors
• more permeable to calcium, increasing motility

Question 35

What is Kallman’s syndrome?

Answer 35

GnRh neurons fail to migrate

-delayed of absent puberty

Question 36

What is Klinefelter’s syndrome?

Answer 36

XXY genotype

• puberty: failure to induce normal testicular growth
• infertile