Looking at a spermatozoon one distinguishes:
- Principal piece
The head contains the condensed nucleus, which is covered on the top by an acrosome, a cap-like vesicle. Hydrolyzing enzymes that play an important role in the penetration of the protective coverings of the oocyte (corona radiata and pellucid zone) are stored in the vesicle.
The acrosome, in terms of volume, takes up around 40% of the head.