POWER AND SYRED / SCIENCE PHOTO LIBRARY POWER AND SYRED / SCIENCE PHOTO LIBRARY
Sperm. Coloured scanning electron micrograph (SEM) of human sperm (spermatozoa), the sex cells of the male. Sperm are about 0.065 millimetres in length. Each head contains genetic material that is transferred to the female egg (ovum) during fertilisation. Their flexible tails enable them to propel themselves along the female reproductive tract. Only one sperm can successfully penetrate the egg and fertilise it. Sperm are formed in the testes by a specialised form of cell division known as meiosis. Each sperm contains 23 chromosomes, including an X or Y sex chromosome. Magnification x4000 at 6x7cm size.
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