The Male Reproductive System
. At reproductive age the testes begin to produce sperm and production continues throughout the male’s adult life. The sperm that are produced in the testes are microscopic; in fact they are so small that it would take 500 of them lined up tail to head to measure one inch. The mature male is capable of having 400 million sperm in each ejaculation.
The part of the testes that manufactures the sperm are the seminiferous tubules. After the sperm are produced they are stored in the epididymis; if the sperm are not used within a couple of weeks they begin to atrophy and the production process begins anew. The epididymis is a series of coiled tubes located on the top of each teste (check diagram for location). If these tubes, the epididymis, were stretched out they would each measure one meter.
Sperm production can be interrupted purposely or due to a medical trauma. The purposeful interruption is a medical procedure called the vasectomy, during this minor surgery the tubes that carry the sperm from the testes to the urethra are severed and tied off. This operation in no way hinders sexual functioning or the production of testosterone. Testosterone, the male hormone, is produced by the testes and is responsible for the onset of the male’s secondary sex characteristics. The testes, which are also referred to as gonads, are located in a sac just under the penis (scrotum).
During sexual excitement the sperm make their way through the vas deferens to the urethra; while in the vas deferens they pass the seminal vesicles, the prostate gland, and the cowper’s gland. These three glands each produce a secretion that mixes with the sperm to make semen. The volume of semen ejaculated during sexual excitement is about one teaspoon.
The Female Reproductive System
. At reproductive age the woman’s ovaries (gonads) usually produce one ovum a month. A female at birth has about 400,000 primitive eggs in her ovaries; however, over her reproductive life only 400 develop to maturity.
During each month of a woman’s reproductive life time a mature egg will actually burst out of the ovary and find its way into the nearest fallopian tube, then slowly move toward the uterus. This trip can be interrupted by the presence of sperm in the tubes as the result of recent sexual intercourse. If there are sperm present the egg will be bombarded before it proceeds through the first third of the fallopian tube. After fertilization (the sperm nucleus combining with the egg nucleus), the egg continues its journey to the uterus. At this point the body becomes aware that it is pregnant and prepares the lining of the uterus (endometrium) to receive the fertilized egg. Nine months (266 days) after the sperm has entered the ovum it becomes a fully functional human being.
What happens during the nine month period, the prenatal period, is the subject of this unit.