ALAIN POL, ISM / SCIENCE PHOTO LIBRARY ALAIN POL, ISM / SCIENCE PHOTO LIBRARY
Sperm cell. Coloured transmission light micrograph (TEM) of a longitudinal section through a sperm cell, or spermatozoon. This is the male sex cell and is produced in the testes. It consists of a tapered head (upper left) that contains the genetic material, a basal body (green and yellow) that contains mitochondria that provide energy for the cell, and a tail (bottom right) that beats to propel the sperm. When a man ejaculates he releases millions of sperm cells, which travel along the female reproductive tract, through the cervix to the uterus (womb) and fallopian tubes, where one may fertilise an ovum (egg). The tip of the head, the acrosome, contains enzymes that are released to help the sperm penetrate the egg.
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