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Human sperm. Coloured scanning electron micrograph (SEM) of human sperm (spermatozoa). Sperm are the motile male sex cells produced in the testes. Each sperm is about 65 micrometers long and broadly divided into rounded head, neck and tail regions. The pear-shaped head contains the nucleus and genetic material of the male needed to fertilize the female egg (ovum). The head is join- ed to the tail by a short neck. The sperm's tail enables it to swim by whiplash movements, an action that propels it to reach the ovum. The semen ejaculated by a man contains about 300 million sperm. Magnification unknown.
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