MOTTA, FAMILIARI, NOTTOLA, ARAGONA, MICARA UNIV. "LA SAPIENZA", ROME / SCIENCE PHOTO LIBRARY MOTTA, FAMILIARI, NOTTOLA, ARAGONA, MICARA UNIV. "LA SAPIENZA", ROME / SCIENCE PHOTO LIBRARY
Human egg. False-colour scanning electron micrograph of a human egg, partly surrounded by spermatozoa (blue), from an in vitro fertilisation programme. The external layer of follicular cells (corona radiata) was removed and the sperm lies on the zona pellucida (pink), a thin but resistant glycoprotein membrane which entirely surrounds the egg. Only one spermatozoon may penetrate this barrier by releasing special enzymes. Once it has entered, the zona pellucida becomes impermeable to the passage of other spermatozoa. In vitro fertilisation is used to alleviate infertility. Magnification: x230 at 6x7cm size. Magnification: x365 at 4x5 inch size.
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