As like all other mammals, human have separate sexes, male and female. The male reproductive system of human consists of the following components:
(1) A pair of sex glands known as testis.
(2) A duct system comprising vasa efferentia, epididymis, ductus deferens, and ejaculatory ducts.
(3) Accessory glands such as seminal vesicles, prostrate, and bulbourethral glands.
(4) Copulatory organ, the penis, containing urethra.
The male sex cells (spermatozoa) are produced by testis, conducted by a variety of ducts and ejected through urethra. A fluid is produced by the secretions of the glands which nourish spermatozoa during the passage. The secretion of glands with spermatozoa is a whitish viscous fluid known as seminal fluid or semen. The process of expulsion of semen from the urethra is called ejaculation.
Sperms are produced in a pair of glands, called Testes. In the male of an adult, the testes is an oval structure, about 4 cm long and weighing around 25 g.
The testes are most important organ of male reproductive system and remain suspended in a pouch, called scrotum, outside the abdominal cavity. They actually develop in the abdominal cavity near the kidneys but migrate to the scrotum shortly before or at the time of birth. Sperm development occurs optimally at temperatures a few degrees below the normal body temperature of 37°C. As scrotum has little or no fatty insulation, it keeps the testes at a temperature cooler than the body temperature. Moreover, a suitable temperature is maintained inside the testes by involuntary movements of the muscles that connect the scrotum to the body wall. Contraction or relaxation of muscles moves the scrotum nearer to or farther away from the heat of the body when environmental temperatures are low or high, respectively.
The outermost layer of the testis is a dense fibrous membrane called tunica albuginea. Internally, each testis is divided into several lobules. Each lobule contains a number of tiny, highly convoluted tubules known as seminiferous tubules. Each tubule is 70-80 cm in length when stretched out. The basement membrane of the seminiferous tubule is lined by highly specialized cells called spermatogonia. Spermatozoa occupy the central part of the lumen of the seminiferous tubule. An another type of cells, known as cells of Sertoli, are also attached to the basement membrane. These cells provide mechanical support and protection to the developing germ cells and also participate in their nutrition and maturation. In between seminiferous tubules, masses of cells called interstitial cells or Leydig cells, are present. These cells secrete the male hormone for performing the male reproductive system.
The duct system of male reproductive system consists of tubes which conduct sperms from the testes to the outside. The seminiferous tubules open into a structure known as rete testis. Several vasa efferentia arise from the rete testis, which open into the epididymis and conduct spermatozoa out from the testis. The epididymis is a long but highly convoluted tube resting upon and on the side of the testis. It has a head, a body and a tail. The head of the epididvmis is made up of highly convoluted continuation of the efferent ductules. At the lower end of the head these tubules join to form a single tube called the duct of epididymis. At the lower end of the tail, the duct becomes continuous with the ductus deferens. The epididymis temporarily stores spermatozoa.
As a part of male reproductive system a partially coiled thick muscular tube from each epididymis ascends into the abdomen. This tube known as ductus deferens, conducts spermatozoa from the epididymis to the base of the urinary bladder. The ductus deferens joins the duct of the seminal vesicle at the base of the urinary bladder to form the ejaculatory duct, which opens into the prostatic part of the urethra. The terminal dilated part of the ductus deferens is called ampulla.
The urethra is also a part of male reproductive system which is about 18-20 cm long; from the urinary bladder it passes through the prostate glands and teds to the penis.