PROF. P. MOTTA / DEPT. OF ANATOMY / UNIVERSITY "LA SAPIENZA", ROME / SCIENCE PHOTO LIBRARY PROF. P. MOTTA / DEPT. OF ANATOMY / UNIVERSITY "LA SAPIENZA", ROME / SCIENCE PHOTO LIBRARY
Fertilisation. False-colour scanning electron micrograph of a human egg almost surrounded by spermatozoa (blue). At the beginning of their trip in the vagina the spermatozoa number about 300 million. The encounter between the egg and the few hundred surviving spermatozoa occurs in the ampullary region of the Fallopian tube. Only one spermatozoon may fertilise the egg and to do this it must penetrate a thick layer of follicular cells (pink) and the inner membrane known as zona pellucida (not visible here). This penetration is aided by enzymes contained in the spermatozoa's head. Magnification: x485 at 6x7cm size. Magnification: x775 at 4x5 inch size.
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