Zona radiata

The zona radiata is a protective outer layer surrounding an ovum (egg) in mammals. It is a glycoprotein-rich structure that helps facilitate sperm binding and prevents multiple sperm from fertilizing the same egg. During fertilization, enzymes from the sperm break down parts of the zona radiata to allow entry. This layer also plays a crucial role in early embryo development and helps prevent polyspermy (fertilization by more than one sperm). In summary, the zona radiata is essential for regulating fertilization and protecting the developing egg before implantation.