The zona pellucida (ZP) is a protein-rich element responsible for maintaining the egg and the embryo with a spherical shape. During fertilisation, spermatozoa have to gradually pass through the ZP until a single spermatozoon reaches the egg cell membrane.
Zona pellucida (ZP)
By Laura Garrido BSc, MSc (embryologist), Patricia Recuerda Tomás BSc, MSc (embryologist) and Sandra Fernández BA, MA (fertility counselor).
Last Update: 12/04/2018