Male Reproductive Physiology
MALE REPRODUCTION
MALE REPRODUCTIVE PHYSIOLOGY
Testis - 2 compartments: interstitial tissue containing the Leydig cells that synthesize and secrete testosterone and the seminiferous tubules that produce spermatozoa and contain Sertoli cells
Leydig cells and testosterone synthesis - Leydig cells mainly produce testosterone - T is a prohormone for synthesis of estradiol (vs. aromatase) and DHT (via. 5-alpha-reductase) - many effects of T are mediated via estradiol (esp in bone and brain) or DHT (secondary sexual characteristics o DHT is converted locally, so will not see high systemic levels ▪ has a higher affinity for androgen receptor, much more potent o T ( estradiol important for neg. feedback (esp at hypothalamus) and epiphyseal closure - LH from ant.pituitary acts at Leydig cells to stimulate synthesis and secretion of T (which will just diffuse out since it is steroid hormone)
Seminiferous Tubules and Spermatogenesis - seminiferous tubules make up bulk of testicular volume - spermatozoa are synthesized within the seminefous epithelium, and pass thru a series of ducts into the epididymis - the seminiferous tubules have Sertoli cells - spermatogenesis under FSH control
Regulation of Testicular Function
Role of GnRH - GnRH released in pulses, to drive pulsatile gonadotropin release from ant. pituitary - Leydig cells respond to this pulsatile release by releasing pulses of testosterone
Negative Feedback Regulation - secretions from testes feedback on the hypothalamus and the anterior pituitary to inhibit the release of LH - the Sertoli cells also produce inhibin which will have a negative feedback on FSH - castrated animals have high levels of FSH and LH o replacing T in these animals brings LH back to normal levels, but not FSH o this is because FSH inhibition also requires inhibin
Function of Sertoli Cells - Junctional contacts between Sertoli
MALE REPRODUCTIVE PHYSIOLOGY
Testis - 2 compartments: interstitial tissue containing the Leydig cells that synthesize and secrete testosterone and the seminiferous tubules that produce spermatozoa and contain Sertoli cells
Leydig cells and testosterone synthesis - Leydig cells mainly produce testosterone - T is a prohormone for synthesis of estradiol (vs. aromatase) and DHT (via. 5-alpha-reductase) - many effects of T are mediated via estradiol (esp in bone and brain) or DHT (secondary sexual characteristics o DHT is converted locally, so will not see high systemic levels ▪ has a higher affinity for androgen receptor, much more potent o T ( estradiol important for neg. feedback (esp at hypothalamus) and epiphyseal closure - LH from ant.pituitary acts at Leydig cells to stimulate synthesis and secretion of T (which will just diffuse out since it is steroid hormone)
Seminiferous Tubules and Spermatogenesis - seminiferous tubules make up bulk of testicular volume - spermatozoa are synthesized within the seminefous epithelium, and pass thru a series of ducts into the epididymis - the seminiferous tubules have Sertoli cells - spermatogenesis under FSH control
Regulation of Testicular Function
Role of GnRH - GnRH released in pulses, to drive pulsatile gonadotropin release from ant. pituitary - Leydig cells respond to this pulsatile release by releasing pulses of testosterone
Negative Feedback Regulation - secretions from testes feedback on the hypothalamus and the anterior pituitary to inhibit the release of LH - the Sertoli cells also produce inhibin which will have a negative feedback on FSH - castrated animals have high levels of FSH and LH o replacing T in these animals brings LH back to normal levels, but not FSH o this is because FSH inhibition also requires inhibin
Function of Sertoli Cells - Junctional contacts between Sertoli