PHYSIOLOGY OF MALE REPRODUCTIVE SYSTEM

1. Formation of Testes Presence of sex-determining region of the Y-chromosome (SRY gene) directs differentiation of the indifferent embryonic gonads into testes

2. Male Reproductive System Pairs of testis Seminal vesicles Penis Prostate gland

3. Testis has 3 types of cells : Germinal epithelium which produces

gametes Sertoli cells whose function is essential for

proper gametogenesis Leydig cells which secrete testosterone

4. Semen = spermatozoa + seminal fluid

5. In response to FSH and testosterone, the sertoli cells support spermatogenesis

6. In response to LH, the leydig cells produce steroids, including testosterone

7.

8. Testosterone (T) Deravatives effect of T in brain are mediated by its

deravatives T can be converted to DHT & others

- or can be converted to estradiol (E) by aromatase- emediates negatives feedback effect of T

9. Secretion of T declines gradually & varyingly in men above 50

Causes un known Not due to low GnRH, LH or FSH because

their levels are elevated

10. Spermatogenesis Germ cells that migrate from yolk sac

during development become spermatogonia (stem cells)

Spermatogonia replicate selves throughout life by mitosis

Give rise to haploid sperm by meiosis. Occurs in wall of STs Spermatogonia & primary spermatocytes are

located outer part of ST Spermatids & mature spermatozoa are

located toward lume Tails of spermatozoa are in lumen

11. Spermiogenesis Is maturation & separation of spermatids

into mature spermatozoa At the end of 2nd meiotic division, 4

spermatids are still interconnected Sertoli cells phagocytize their cytoplasm &

flagellum & acrosome develop At the end of the spermiogenesis,

spermatozoa are release into lumen

12. Sertoli cell Function Autoimmune destruction of developing

sperm is prevented by blood-testes barrier created by sertoli cells

And by sertoli-secreted FAS ligand that triggers apoptosis of T cells

Spermatogonia & developing spermatozoa are embedded in & nurtured by adjacent sertolis

Sertolis secretes androgen-binding protein (ABP) into lumen of STs

ABP binds testosterone, concentrating it in tubules

FSH stimulates spermiogenesis through its receptors on sertoli

Sertolis provide negative feedback on FSH via production of inhibin

13. Functions of sertolis cells 1) Provided sertoli cell barrier to chemical

in the plasma2) Boorish developing sperm3) Secrete luminal fluid, including

androgen-binding protein4) Respond to stimulation by testosterone

and FSH to secrete paracrine agents that stimulate sperm proliferation and differentiation

5) Secrete the protein hormone inhibin, which inhibits FSH secretion from the pituitary

6) Secrete paracrine agents that influence the function of Leydig cells

7) Phagocytize defective sperm8) Secrete, during embryonic life, mullerian

inhibiting substance (MIS), which causes the primordial female duct system to regress.

hypothalamus

Ant pituitary

Intestinal (leydig) cells

Seminiferus tubules

testosteroneinhibin

FSH LH

-

--

testis

14. Effect of testosterone in male 1) Required for initiation and maintainance

of spermatogenesis (acts via sertoli cells)2) Decreases GnRH secretion via action on

the hypothalamus3) Inhibits LH secretion via a direct action

on the ant pituitary4) Induces differentiation of male accessory

reproductive organs and maintain their function

5) Induces male secondary sex characteristics opposes action of estrogen on breast growth

6) Stimulates protein anabolism, bone growth and cessation of bone growth

7) Required for sex drive anad may enhance aggressive behavior

8) Stimulates erythropoietin secretion by the kidneys.

15. Spermatozoa Have oval shape head that contains DNA &

the acrosome (a cap of digestive system) Have a midpiece & flagellar tail Tail will become motile in epididymus

16. Male accessory sex organs Spermatozoa entering epididymis are nion-

motile & cannot fertilize In part because pH is low Spermatozoa mature & become motile in

epididymis Prostatic fluid neutralizes pH during

ejaculation Vas deferens carries sperm into pelvic cavity Seminal vesicles add fluid (constituting 60%

of ejaculate) to that coming from epididymis(contain fructose for energy for sperm)

Vas deferens becomes ejaculatory ducts which merges with urethra in prostate

Fluid becomes semen when prostate adds secretions containing citric acid, kalsium & coagulation proteins ( which coagulate semen during ejacvulation)

17. Erection Is controlled by hypothalamus & sacral cord Occurs as result of parasymp-induced blood

flow into erectile tissues of penis NO is NT Erectile tissues include corpus cavernosum

& spongiosum Venous outflow is partially accluded, aiding

erection

18. Emission & ejaculation Emission is movement of semen into urethra Ejaculation is forcible expulsion of smen

from urethra out of penis Both are stimulated by sympathetic activity

Which also causes peristalsis of tubular system, contractions of seminal vesicles, prostate, & muscles at base of penis

19. Semen Characteristics About 2 to 5 ml per ejaculation Comprise about 10% sperm, 60% secretion

from seminal vesicles, 30% prostatic secretions

pH 7.4 Normal count 40 – 100 million/ml Survival period in female genital tract is 24-

72 hours

20. Semen abnormalities Presence of WBC indicate infection Sperm count < 20 million/ml indicates

oligospermia

21. Factors affecting sperm quality Testicular injury/disease eg.mumps Heat exposeure Severe allergic reaction Lead or arsenic poisoninh Exposure of radiation Endocrine disorder e.g. diabetes mellitus Drugs including marijuana, cocain &

anabolic steroids