DAVID SCHARF / SCIENCE PHOTO LIBRARY. DAVID SCHARF / SCIENCE PHOTO LIBRARY.
False colour scanning electron micrograph (SEM) of a field of human sperm, showing the division of a single spermatozoon into a head & tail section. The sperm's tail enables it to swim, an essential action in reaching the female ovum. The mature male sex cell (male gamete) is carried in the head, the top part of which is capped by the acrosome, which breaks down just before fertilisation, releasing enzymes which assist in the penetration of the follicle cells that surround the ovum. Only a single sperm succeeds in penetrating & fertilising the ovum; rapid changes in the wall of the ovum prevent further penetration. Magnification: X760 at 35mm size. Original is bw print p624/029.
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