Illustration of a human sperm fertilising an egg. The picture shows the size difference between the egg,or ovum,& the spermatozoon. Human spermatozoa are extremely elongated single cells about 65 micrometres long,divided into 3 main regions: a head,neck,& tail. The head,which contains the male nucleus,is about 7 micrometres long. Here,the head appears buried in the follicular cells,which form the corona radia that surrounds the ovum. Beneath the corona radiata is a glycoprotein membrane,the zona pellucida,which the sperm must penetrate to reach the female nucleus. This version on black background. Version on white background is P648 010 |