17 - PHYSIOLOGY OF REPRODUCTION- Male reproductive system. Spermatogenesis, Male sex hormone (androgens) – types, physiologic effects and control of secretion. Erection and ejaculation.

sections

what is reproduction what does it involve in humans

male reproductiev system

spermatogenesis

Sertoli cells

male sex hromones

erection and ejaculation

what is reproduction what does it involve in humans

• Reproduction is the process by which organisms create offspring.

• In human reproduction, the male and female sex cells are involved.

male reproductiev system

consists of the testes and a series of ducts and glands.

• Sperm are produced in the testes and transported through the reproductive ducts.

• These ducts; epididymis, vas deferens, urethra.

• The reproductive glands produce secretions that form semen

• These glands include the seminal vesicles, prostate gland, and bulbourethral glands.

spermatogenesis

• Spermatogenesis -process where spermatozoa are produced by primordial germ cells.

• Spermatogonium→primary spermatocytes are produced by mitosis.

• The primary spermatocyte divides → two secondary spermatocytes by Meiosis I

• each secondary spermatocyte divides → two spermatids by Meiosis II

• Spermatids develop into mature spermatozoa, called sperm cells.

In total they four spermatozoa produced. It is a non-interrupted process. Optimum temp

Sertoli cells role in spermatogenesis

• Secretes inhibin which inhibit FSH

  • FSH stimulates Sertoli cells, which are essential for nurturing developing sperm. When FSH binds to receptors on these cells, it promotes the production of androgen-binding protein (ABP) and other factors that support sperm cell development.

  • FSH works hand in hand with luteinizing hormone (LH). While LH stimulates Leydig cells to produce testosterone, it's the combined effect of testosterone (from LH action) and FSH that fully supports spermatogenesis.

male sex hromones

• Androgens are steroid hormones, involved in the control of the development and maintenance of male characteristics

• Androgens are precursors of all oestrogens. - - etc. - - - - testosterone.:

• The androgenic affects include- deepening of the voice, facial hair growth, growth differentiation of embryonic penis, increase muscle mass

• Feedback regulation of the hypothalamic-pituitary-testicular axis in males

• Other androgen- Dihydrotestosterone- DHT- in embryo causes differentiation of penis, scrotum and prostate

• DHEA- dehydroepiandrosterone

• Androstenedione

erection and ejaculation

Erection

• stimulated by testes of the parasympathetic nervous system

• During sexual arousal, impulses from the brain cause the muscles of the corpora cavernosa to relax.

• This allows blood to flow in and fill the open spaces.

• Vasodilation of arteries in penis

• The blood creates pressure in the corpora cavernosa causing the penis to expand causing erection.

• Erection is stopped when parasympathetic stimulation stops. muscle in penis contract stopping blood influx and opening outflux channels.

Ejaculation

• stimulated by sympathetic nervous system

• When the sexual act reaches a critical level of excitement., sympathetic impulses

• 2 phases:

  • first phase- vas deferens contracts causing sperm to squeeze to the lower base of the penis.

  • second phase- muscles of the base of the penis contract every 0.8 s ejaculating semen. Ejaculate from the urethra—emission and propulsation