Human Male Reproductive System

Human male reproductive system consists of the following main organs:

1. Primary Sex Organs
2. Secondary Sex Organs
3. External Genitalia

1. Primary Sex Organ: The organs which produce sex cells or gametes and sex hormones are called Primary Sex Organs. Testes is the PSO of Human male. It is 2 in number. The testes are located outside the abdominal cavity within a pouch called Scrotum. This position is called extra-abdominal position. Scrotum provides a temperatures 2-2.5 degree C lower than the body temperature. It is due to the fact that formation of sperms (=spermatogenesis) requires low temperature.  

structure of Testis

Each testis is oval in shape. It measures about 5 cm in length, 2-3 cm width and about 3 cm in thickness. The  testis is covered by a dense covering called tunica albuginea. Internally the testis is divided into about 250 compartments called testicular lobules. Each lobule contains 1-3 highly coiled seminiferous tubules. Seminiferous  tubules are the structural and functional units of testis. Sperms are produced in the testis. The seminiferous tubule is internally lined bu germinal epithelium. The germinal epithelium consists of 2 types of cell : Sertoli cell and Male germ cell (Spermatogonia). Sertoli cells provide nutrition and shape to the developing germ cells and spermatozoa. The spermatogonia undergo cell divisions to form spermatozoa. The spaces between two seminiferous tubules have Leydig cells or Interstitial cells which synthesize and secrete the male sex hormones called androgens or Testosterone. 

2. Secondary Sex Organs: The organs which conduct gametes and sex hormones are called SSO. Duct system and Accessory glands are SSO. 

Duct System: The seminiferous tubules connect and form network called rete testis. From the rete testis arise 10-20 fine tubes called vasa efferentia. They open into the epididmis. The epididmis is a single convoluted tubule that is located along the posterior surface of the testis. The epididmis continues as the vas deferens or sperm duct. It loop over the urinary bladder and receives a duct from the seminal vesicle to form ejaculatory duct that runs through the prostate glands. The urethra receives the ducts of prostate gland and the Bulbourethral (Cowper's) gland and runs through the penis to its external opening called urethral meatus. 

Accessory glands: The accessory glands of male reproductive system include a pair of seminal vesicles, a prostate gland and a pair of Cowper's gland. Their secretions are collectively called as seminal plasma. Seminal plasma is rich in fructose, calcium and certain enzymes. It provides nutrition and a medium for the spermatozoa to swim in the female reproductive tract. The seminal plasma along with the spermatozoa is called semen. 

3. External Genitalia : Penis is the external genitalia in human males. It is made of special erectile  tissue that helps in erection of the penis to facilitate insemination. The enlarged tips of the penis is called glans penis. It is covered by a loose fold of skin  called fore skin or perpuce.