Every living thing goes through a reproductive process to make copies of itself. In the animal kingdom, the movement of sperm is universal no matter what the source — a fact that has allowed space shuttle research on the effects of gravity on sperm locomotion. Interestingly, the sperm studied came from sea urchins.
Human males start producing sperm cells when they reach puberty . . . millions and millions of cells every day. A single sperm is about 1/600th of an inch long, from tiny head to tiny tail. All of these cells develop in the testicles in a system of miniature tubes.
Sperm use their tadpole-like tails first for traveling to a place called the epididymis, where they hang out for about 4 to 6 weeks completing their development. Then they head over to the sperm duct, or vas deferens, where they join up with seminal fluid for their final journey.
During sexual intercourse, sperm is forced out of the guy's body through his urethra. This process of ejaculation liberates up to 500 million sperm at a time. If the sperm are released in a female's vagina, the crowd scurries up through the cervix and the uterus, coached on by chemical signals that prompt the sperm's flagellum (tail) to wiggle. They're all looking to bump into a mature egg in one of the woman's fallopian tubes. If a single sperm manages to break into an egg that just happens to be in the right place at the right time, conception occurs.
The fertilized egg, or zygote, carries the genetic material from both the sperm and the egg — 46 chromosomes of defining material. That zygote goes about the business of dividing over and over, becoming an embryo, then a fetus, then a brand-new baby.