BSIP / SCIENCE PHOTO LIBRARY BSIP / SCIENCE PHOTO LIBRARY
Human sperm. Coloured transmission electron micrograph (TEM) of a human sperm (spermatozoon), showing the head, middle piece and tail. The head (upper right) contains a nucleus that houses the 23 paternal chromosomes of the male gamete. It is capped by the acrosome (pink, surrounding head) which releases enzymes onto the oocyte of the female during fertilisation. This aids penetration of one sperm into the oocyte. The middle piece contains many mitochondria (dark purple bodies, centre) which provide the energy required for the sperm to swim along the female's reproductive tract. It does this by rapidly moving its tail (lower left). Magnification unknown.
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