Fertilisation. Coloured scanning electron micrograph (SEM) of a sperm (blue) penetrating a human egg (ovum). Each sperm (spermatozoan) has a rounded head (acrosome) and a long tail with which it swims. Women usually release one egg per month, whereas men release millions of sperm in each ejaculation. Only one of these sperm can penetrate the egg's thick outer layer (zona pellucida) and fertilise it. Fertilisation occurs when the sperm's genetic material (deoxyribonucleic acid, DNA) fuses with the egg's DNA. When this occurs the egg forms a barrier to other sperm. | |
Licence : | Droits gérés |
Crédit: | Science Photo Library / Clouds Hill Imaging |
Taille de l’image : | 2995 px × 2995 px |
Model Release : | Non requis |
Property Release : | Non requis |
Restrictions : | - |