ells to move. Millions of sperm cells mature constantly in males, rather than just one cell per month as egg cells do in females. The male body can produce sperm cells until age 80 or 90.
             A boy also produces a slippery fluid called semen, which mixes with the sperm cells. Occasionally he will have such a build up of semen that his body will automatically release it.
             This is called nocturnal or seminal emission. It is also referred to as a "wet dream" since it happens often during sleep.
             As an egg cell matures, or ripens, it's released by the ovary. It is quickly drawn into a tube called the fallopian tube or oviduct, which connects the ovary with the uterus. The tube is about three to five inches long and is lined with tiny hair-like projections which move back and forth. These hair-like projections brush the egg cell along on its journey. It takes the egg three to four days to reach the uterus, whether it is fertilized or not.(Child Birth,733)
             If there are live sperm cells in the fallopian tube, they will bump into the egg cell and surround it. Sperm cells make an enzyme or chemical, which will dissolve the tough membrane around the cell.
             After great many sperm cells have bumped into the egg cell and deposited this enzyme, some of the membrane will be dissolved. Then the next sperm cells to bump into the egg cell will go right through into the egg.
             Many sperm cells may enter the egg cell, but only one sperm head or nucleus can unite with the egg cell's nucleus.
             The first sperm cell to reach the nucleus of the egg will live. All the rest will die in a few hours.
             One major difference between sex cells and all other human tissue cells is that sex cells do not have the normal number of chromosomes, or heredity-determining factors. All other cells have 46 chromosomes. Egg cells and sperm cells are half complete, having only 23 chromosomes. When the two nuclei of the sex cells meet and unite, they form a...