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| Home > Reproductive Anatomy > Male Sexual and Reproductive Organs
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| | Male Sexual and Reproductive Organs
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 The source of sperm or spermatozoa is the testis. In human beings, the two testes or testicles are enveloped in a sac of skin, the scrotum, lying below and outside the abdomen. The testes are the source of hormones that cause full development of secondary sexual characteristics and also the proper functioning of the genital (reproductive) tracts. These tracts comprise the penis, the sperm channels-epididymis, ductus deferens, and ejaculatory ducts-and other related structures and glands. The scrotum and the penis form the external genitalia of the male.
About 800 small tightly coiled tubes called seminiferous tubules exist in each of these testicles and produce millions of sperms in response to a hormone produced by the pituitary gland in the brain. A second hormone from the pituitary gland causes the testicles to produce the male sex hormone, testosterone, responsible for ensuring adequate production of sperms as well as development of secondary sexual characteristics like deep voice, facial and body hair etc. The epididymis is a wide coiled tube that is utilized for storing the sperms until they are mature and motile. The epididymis is formed through joining and extending the seminiferous tubules. The vas deferens is a duct that carries and stores the sperms. The epididymis becomes the vas deferens as it leaves the scrotum and enters the pelvic cavity. The motility and fertility of the sperms in the vas deferens are enhanced by nourishment with fluids secreted by the seminal vesicles, the prostate gland, and Cowper`s glands. The sperms together with these secretions make up the semen or seminal fluid.
The urethra is an extension of the vas deferens and leads from the bladder to the end of the penis. It serves the dual purpose of carrying urine from the bladder as well as semen from the vas deferens. Normally, the penis is soft or flaccid. On sexual arousal, blood fills into the tissues of the penis causing it to expand and firm. The firmness allows the insertion of the penis into the vagina during copulation. Muscles also contract to close the duct to the bladder to keep urine out of the semen. At the sexual climax, ejaculation occurs through involuntary muscle contractions, propelling semen through the urethra into the female genital tract. The usual volume of semen in each ejaculation is about three milliliters (less than a teaspoon) containing 150 million to 450 million sperms.
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