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
Human egg. False-colour scanning electron micrograph of a human egg (primary oocyte) at the end of the first meiotic division, occurring just before ovulation. At this stage the primary oocyte is split into two cells, known as the secondary oocyte (green) and the first polar body (yellow), each containing 23 chromosomes. If after ovulation the secondary oocyte is penetrated by a spermatozoon, it completes the second meiotic division producing a fertilised mature oocyte and one polar body. The first polar body divides into two and all three polar bodies shortly degenerate. Magnification: x700 at 6x7cm size.
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