The Male Reproductive System

The male reproductive system consists of the testes and a system of excretory ducts and their accessory structures. In descending order these organs include: the testes, a pair of oval bodies lying in the scrotal sac. The testes have two major functions: to produce the male sex hormone, testosterone, and to produce sperm. The male does not function in a cycle as the woman does. His production of sperm and hormones remains relatively constant, even when he is not sexually active. After production, the sperm pass slowly through the epididymis for several months, where they undergo maturation and attain motility.

Connected to the epididymis are two long ducts, called the vas deferentia (singular: vas deferens). The bottom end of the vas deferens, where it leaves the epididymis, is the site of vasectomy in males who undergo this procedure. These thick-walled tubes are in a state of constant muscular action that gently "squeezes" sperm along the way to the upper end, where the vasa deferentia widen out to form the ampullae. Sperm are stored here prior to ejaculation. Beyond the ampullae are two offshoots of the vasa deferentia, called the seminal vesicles. These glands are important for their production of the sugar fructose, which is needed as fuel by the sperm for their long journey.

Just after the opening of the seminal vesicles at the base of the bladder lies the prostate gland, which contributes most of the actual seminal fluid and an important chemical or enzyme that causes the semen to liquify from its coagulated state shortly after ejaculation. The secretion of the prostate is highly alkaline to neutralize the acidity of the urethra and also the environment of the woman's vagina. Beyond the prostate, situated at the base of the penile shaft in the urethra, are a pair of small glands, called Cowper's glands, that add a small amount of lubricant to the seminal fluid before ejaculation takes place. Finally, there is the penis, the organ of copulation, by means of which the seminal fluid is deposited in the vagina of the woman. The penis contains cavernous spaces that have the capacity to fill with blood when stimulated, which results in erection and rigidity of the organ for intercourse.

The following sequence will further illustrate the events that take place during intercourse: Sperm are produced in the testes and stored in the epididymis for several months of maturation. At the time of excitation (physical or mental) the vasa deferentia increase the upward contractions of their muscular walls, sending more sperm into the ampullae. Upon ejaculation, the seminal vesicles, the prostate, and Cowper's glands all add their secretions to the sperm, making semen or seminal fluid. The ejaculate is discharged through the erect penis. A normal ejaculation contains anywhere from 40 to 500 million or more highly active sperm in a quantity of about 2 to 5 cc of semen.