For many years before a baby is conceived, the bodies of his parents have been getting ready for his conception. The mother's body has been producing egg cells (ova), and the father's sperm cells (spermatozoa) to fertilize them. Once an egg is fertilized, the baby needs a place to grow and develop; the mother's body has prepared such a place.
             When a girl reaches her teens her body begins to change, making it possible for her to produce and carry a baby. Her hips widen so that the pelvic cavity is large enough to hold a baby and allow it to pass through the birth canal. Her breasts enlarge so that after the baby is born, she can supply milk for him.
             Many changes are also going on insider her body. Each month one egg cell (ovum) is maturing and being released from one of her two ovaries. The ovaries are the storage place for undeveloped egg cells. An egg cell looks something like a hen's egg, except that it is the size of a pinpoint. It has a yellow center with a fluid around it. The outer covering or membrane is tough, but not as hard as a hen's egg shell.
             Each month the uterus, of womb, where the baby will grow, develops a special lining of blood vessels, which can nourish a baby. If an egg is not fertilized, it continues on its path through the birth canal to the outside. Then the special lining in the uterus pulls away from the uterus wall and also passes on to the outside, since it is not needed to nourish a baby. The process by which this lining is discarded is called menstruation. A girl's body will prepare an egg cell and a fresh lining in the uterus approximately every month from the time she is 12 or so until she is in her 40s or 50s.
             A boy also begins preparing for fatherhood early in his teens.(Child Birth,732) At the time sperm cells, will start maturing. Sperm cells are much, much smaller then egg cells. They look somewhat like a tadpole with a round head and long tail. This tail makes it possible for the sperm c...