12. Male Reproductive Physiology

Question 1

What distinguishes gonadal sex and phenotypic sex

Answer 1

Gonadal- testes or ovaries

Phenotypic- physical characteristics of internal genital tract and external genitalia

Question 2

What are the main gonadotropin hormones

Answer 2

FSH and LH

Question 3

How do levels of FSH and LH compare in childhood and puberty/adulthood and senescence

Answer 3

Childhood- FSH > LH
Puberty/Adulthood- LH > FSH
Senescence- FSH > LH

Question 4

What initiates puberty

Answer 4

Pulsatile secretion of GnRH which drives the pulsatile secretion of FSH and LH

Question 5

What happens if a long-acting GnRH analogue is administered

Answer 5

Puberty is not initiated

-If a GnRH analogue is administered in intermittent pulses puberty is initiated and reproductive function is established

Question 6

What are the main general functions of the testes, scrotum and epididymis

Answer 6

Testes- spermatogenesis and secretion of testosterone
Scrotum- lower temperature below body temperature
Epididymis- primary location for maturation and storage of sperm

Question 7

What are the main general functions of the Vas deferens and the Prostate gland

Answer 7

Vas Deferens- storage for sperm, nourish sperm (fructose), seminal vesicles (adds 2/3 fluid)
Prostate Gland- secrete milky aqueous solution rich in citrate, calcium and enzymes

Question 8

What makes up seminiferous tubules

Answer 8

Epithelium formed by the Sertoli cells with interspersed germ cells

• Spermatogonia (immature) are in the periphery
• Spermatozoa (mature) are near the lumen

Question 9

What makes up the testis

Answer 9

80% seminiferous tubules

20% CT with Leydig cells

Question 10

What is the general function of Sertoli cells

Answer 10

‘Nursing Cells’

• Form tight junctions to control sperm environment
• Provide nutrients to the sperm
• Helps transport sperm through tubules into epididymis

Question 11

What is the general function of Leydig cells

Answer 11

Synthesis and secretion of testosterone

Question 12

What is the function of 17B-Hydroxysteroid in male physiology

Answer 12

-Converts androstenedione to testosterone

Question 13

In the periphery what activates testosterone in target tissue

Answer 13

5a-reductase converts T to DHT

lack of enzyme results in ambiguous external genitalia

Question 14

What is responsible for steroid synthesis in the testis

Answer 14

Leydig cells synthesize cholesterol de novo and store cholesterol as esters

• generated via Hormone-Sensitive Lipase (HSL)
• cholesterol is transferred via StAR
• cholesterol converted to pregnenolone

Question 15

How do males get estrogen

Answer 15

• Aromatase (CYP19) converts testosterone to estradiol in sertoli cells
• Most estrogen made in adipose tissue

Question 16

What is the rate-limiting step in synthesis of testosterone

Answer 16

Conversion of cholesterol to pregnenolone by P450SCC

Question 17

How is testosterone concentrated in seminiferous tubules

Answer 17

binding to ABP

Question 18

What role does LH play in testosterone synthesis

Answer 18

Promotes pregnenolone synthesis via

• increasing affinity of P450SCC for cholesterol
• stimulate synthesis of P450SCC

Question 19

How does most of testosterone circulate

Answer 19

60% bound to sex hormone-binding globulin (SHBG)
38% bound to albumin
2% free

Question 20

What does DHT due embryologically

Answer 20

External Genitalia (penis prostate and scrotum)

Question 21

What are some anabolic actions of androgens

Answer 21

• Stimulation of erythropoietin synthesis
• Stimulation of sebaceous gland secretion
• Stimulation of ABP synthesis
• Nitrogen retention

Question 22

What is Benign Prostastic Hyperplasia (BPH)

Answer 22

• Patients might have more DHT receptors on prostates but do not have more DHT in prostastic receptor
• Patients have prostate peeing issues

Question 23

What are the intracellular mechanism of action of testosterone

Answer 23

cAMP-PKA pathway for both LH and FSH

FSH- uses pathway to synthesize ABP and aromatase

Question 24

What are the three stages of Spermatogenesis

Answer 24

1. Mitotic divisions
2. Meiotic divisions
3. Spermiogenesis

Question 25

Describe the mitotic division phase of Spermatogenesis *spermatocytogenesis)

Answer 25

- Proliferative phase - At puberty, mitotic cycles increase and spermatogonia or stem cells divide to produce daughter spermatogonia - After last division the resulting cells are called primary spermatocytes

Question 26

Describe the meiosis phase of Spermatogenesis

Answer 26

- Production of the haploid gamete - Primary spermatocytes undergo two meiotic divisions - First division produces two secondary spermatocytes, each with a haploid number of duplicated chromosomes - Secondary spermatocytes enter second meiotic division, producing two spermatids, each with a haploid number of unduplicated chromosomes

Question 27

Describe the spermiogenesis phase of Spermatogenesis

Answer 27

- Spermatids undergo spermiogenesis and mature into spermatozoa - Nuclear and cytoplasmic changes to produce mature spermatozoa - Ends in testis with release of spermatozoa from Sertoli cells

Question 28

What are the three major hormonal factors that stimulate spermatogenesis

Answer 28

LH FSH GH

Question 29

What are the two main differences the male reproductive tract has

Answer 29

- Continuous lumen from seminiferous tubule to the end of the male tract - Male tract connects to the distal urinary tract

Question 30

What role do parasympathetics play in erection

Answer 30

- Innervates vascular SM of the helicine arteries that supply blood to the cavernous spaces release NO - Vasodilation allows blood to flow into spaces, causing engorgement and erection - Engorged tissue presses the veins against a noncompliant outer fascia, reducing venous drainage

Question 31

How does Viagra work

Answer 31

- NO activates guanylyl cyclase to make cGMP | - cGMP prolongs the erection so viagra inhibits Type 5 phosphodiesterase which degrades cGMP to GMP

Question 32

What is the male sexual response of Emission

Answer 32

Movement of semen from the epididymis, vas deferens , seminal vesicles and prostate to the ejaculatory ducts

Question 33

What happens when there is a lack of testosterone (gonadal dysfunction) in the 2-3rd months of gestation vs 3rd trimester of pregnancy

Answer 33

2-3 months = ambiguity in male genitalia | 3rd trimester = problems with testicular descent (cryptorchidism) and micropenis

Question 34

What happens when there is a lack of testosterone (gonadal dysfunction) in puberty vs post-pubery

Answer 34

``` Puberty = poor secondary development and overall eunuchoid features Post-Puberty = decreased libido, ED, low hair and energy, infertility ```

Question 35

What is Kallman's Syndrome

Answer 35

Genetic disorder where GnRH neurons fail to migrate into the hypothalamus during embryological development - Delayed or absent puberty and an impaired sense of smell - Form of hypogonadotropic hypogonadism (SECONDARY)

Question 36

What is Klinefelter Syndrome

Answer 36

Seminiferous tubular dysgenesis- male with an extra X chromosome - at puberty gonadotropins levels fail to induce normal testicular growth and spermatogenesis - low androgen production but high gonadotropins indicating PRIMARY HYPOGONADISM

Question 37

What does Hyperprolactinemai do

Answer 37

suppresses FSH and LH secretion