The major function of the male and female reproductive systems is procreation. The two systems work together in a complementary fashion to join a sperm and an egg at the moment of conception to create a new human being.
There are approximately 20 million sperm in a normal sample amount; however, only one sperm is needed for conception, or fertilization of the egg, to occur.
The male reproductive system shares some structures with other body systems: The penis and urethra are shared by the urinary system, and the testes are shared by the endocrine system. Other structures within the male reproductive system include the prostate gland, the scrotum, and a series of ducts and glands (Fig. 11-1).
The male reproductive system.
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The testes are located within the scrotum. They are oval-shaped structures composed of an outer capsule, made of thick, white connective tissue, and an inner part divided into 200 to 300 lobules, which contain the seminiferous tubules. Spermatogenesis (creation of sperm cells) occurs in the seminiferous tubules. Spermatocytes are the male reproductive cells, which carry half of the genetic material needed to form a new human being. These cells are sensitive to heat and must live within an environment that is slightly below normal body temperature.
Therefore, prior to birth, the testes in the male fetus normally descend from the lower abdomen into the scrotum. The scrotum is composed of two internal compartments surrounded by loose connective tissue and a smooth muscle layer. A second muscle group, called the cremasters, extends from the abdomen into the scrotum. The structures of the scrotum are designed to maintain an optimal temperature for spermatogenesis. In a cold environment, the smooth muscle of the scrotum and the cremaster muscles contract, bringing the scrotum and testes closer to the body to keep them warmer. In a warm environment, the same muscles relax and allow the scrotum and testes to descend away from the body to keep them cooler.
When spermatocytes have reached a sufficient stage of maturity, they exit the testes through a series of ducts beginning with the seminiferous tubules, then the rete testis, efferent ductules, epididymis, vas deferens, and finally the ejaculatory duct, which joins with the urethra. From there, they exit the body during ejaculation.
The penis is composed of three sections ...