Anatomy And Physiology of Male Reproductive System
• Male reproductive organs consist of :
• Paired testicles in the scrotum
• Epididymis
• Vas deference ( seminal duct)
• Seminal vesicles
• Penis
• Prostate gland
• Cowper’s gland (bulbourethral gland)
• Ejaculatory ducts
• Among the male reproductive structures only the scrotum and penis are external and other structures are internal.
• Male perineum the area between scrotum and anus.
Penis :
• It is both a sexual organ as well as organ for urination.
• Portion of both penis between its attachment to the public bone and to the head of the penis is known as shaft.
• External opening of the urethra is in the glans and is covered by foreskin or prepuce.
• Penis is homologous to female clitoris
• Penis is flaccid but during the time of erection it becomes rigid because corpora cavernosa fills with blood.
• Following ejaculation blood leaves the penis and it becomes flaccid.
Scrotum and Testes :
• Scrotum is a double pouch hanging at the base of penis.
• Scrotal pouch is internally separated I to halves by muscular contractile tissue known as tunica dartos, externally separated into the two halves by raphe (ridge).
• Seperms are produced at seminiferous tubules and stored in epididymis.
• Testicles produce male hormone testosterone and sperm.
• Vase deference is the continuation of epididymis and it continues with the ejaculatory duct and tha conveys semen into urethra.
• Vas deference is the exactory duct of the testicle, and is the target in vasectomy.
• Each half of the scrotum contains testicle with its epididymis and part of the spermatic cord is held together by spermatic fascia.
Sperm:
• They are mature male sex cells.
• Sperm have self-propelling capacity with the help of flagella.
• A normal sperm has an oval-shaped flattened head with nucleus, middle piece or protoplasmic neck and a tail.
• During fertilization, sperm head penetrates the ovum and tail part is lost.
Prostate and Related Structures
• Prostate gland surrounds male urethra and urinary bladder.
• Adult prostate gland weight 15 to 20 gram and is 4 to 6 cm long.
• Adult prostate gland weight 15-20 gm and is 4-6 cm long
• Posterior surface of the prostate in close contact with rectal wall, and is the surface available for digital examination.
• Portion of urethra that passes through the prostate is known as prostatic urethra.
Male Sexual Devlopment And Function:
• Devlopment of male genitalia requires two hormones.
• Mukerian duct inhibitory factor secreted by seroli cells
• Testosterone secreted by Leydig cells.
• Hypothalamus secretes GNRH which stimulates the pituitary gland to produce LH and FSH.
• LH stimulates leydig cells to produce testosterone.
• Testosterone and FSH stimulate sertoli cells to start and complete spermatogenesis.
• Inhibin released from sertoli cells give negative feedback to the anterior pituitary.
Spermatogenesis :
• Production and maturation of sperm in the seminiferous tubules is known as spermatogenesis.
• This process starts at puberty because of stimuli from anterior pituitary.
• Spermatogonia are the geminal cells and a portion continues to develop as sperm.
• During 24 days, when they are in contact with sertoli cells spermatogonia change and enlarge to from primary spermatocytes.
• Primary spermatocytes. divides and forms two secondary spermatocytes each with half number of chromosomes.
• Secondary spermatocyte undergo the next division after 2-3 days and become four spermatids each with half the number of chromosomes.
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Writer: Vandita Singh, Lucknow