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Home > All Images > 1999 > December > 7 Dec 1999

Images Dated 7th December 1999

Choose from 12 pictures in our Images Dated 7th December 1999 collection for your Wall Art or Photo Gift. Popular choices include Framed Photos, Canvas Prints, Posters and Jigsaw Puzzles. All professionally made for Quick Shipping.


Computer artwork of human sperm fertilising an egg Featured 7 Dec 1999 Print

Computer artwork of human sperm fertilising an egg

Sperm fertilising egg. Computer illustration of sperm cells (white) approaching a human egg (pink), before one of the sperm fertilises it. Women usually produce one large egg (ovum), whereas men release some 300 million much smaller sperm (spermatozoa) which travel with whiplash movements of their tails through the uterus to reach the egg. A few hundred sperm survive this journey and encounter the egg in the fallopian tube. Only one sperm can penetrate the egg's thick outer layer (zona pellucida) and fertilise it by fusing with its DNA (deoxyribonucleic acid) genetic material. When this occurs, the egg membrane forms a barrier to other sperm

© DAVID GIFFORD/SCIENCE PHOTO LIBRARY