STEVE GSCHMEISSNER / SCIENCE PHOTO LIBRARY STEVE GSCHMEISSNER / SCIENCE PHOTO LIBRARY
Maturing sperm. Coloured freeze-fracture scanning electron micrograph (SEM) of healthy spermatozoa (sperm, yellow) in the epididymis (red). Sperm cells are the male sex cells. They are produced in the testes and are responsible for fertilisation of the female ovum (egg). The epididymis is a long convoluted tube connecting the testes to the vas deferens. Here, a cross-section has been taken across two of its coils, making it appear as three separate tubes. Magnification: x300 when printed 10 centimetres wide.
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