CIL:39092 - http://cellimagelibrary.org/images/39092
Description: Light micrograph of human ovum (egg) and sperm. The ovum is much larger than the sperm and is surrounded by protective cumulus cells around the outside surface (yellow). The membrane surrounding the ovum (brown) is the zona pellucida. The head of the sperm carries special enzymes to dissolve the zona pellucida, which is required in order to fertilise the egg.
Author: Spike Walker
Licensing: Attribution-NonCommercial-NoDerivs 2.0 UK: England & Wales (CC BY-NC-ND 2.0 UK)