Physiology Of Male

PHYSIOLOGY OF MALE REPRODUCTIVE SYSTEM 1.

Formation of Testes Presence of sex-determining region of the Ychromosome (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.

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hypothalamus -

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Ant pituitary

FSH

LH testosterone

inhibin Seminiferus tubules

Intestinal (leydig) cells

testis

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 plasma 2) Boorish developing sperm 3) Secrete luminal fluid, including androgen-binding protein 4) 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 sperm 8) Secrete, during embryonic life, mullerian inhibiting substance (MIS), which causes

the primordial female duct system to regress. 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 hypothalamus 3) Inhibits LH secretion via a direct action on the ant pituitary 4) 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 nionmotile & 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

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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 2472 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