The thick membrane of the<unk>  functions to only allow species-specific fertilization; to prevent polyspermy, and enable the acrosome reaction for the successful adhesion and penetration by the sperm cell. Also allows correct embryo development and size. The major glycoproteins of the egg coat responsible, are known as sperm-binding proteins. The four major sperm-binding proteins, or sperm-receptors, are<unk> 1,<unk> 2,<unk> 3, and<unk> 4. They bind to capacitated spermatozoa and induce the acrosome reaction. Successful fertilization depends on the ability of sperm to penetrate the extracellular matrix of the<unk>  that surrounds the egg. In the mouse: *<unk> 3 allows species-specific sperm binding *<unk> 2 mediates subsequent sperm binding *<unk> 1 cross-links<unk> 2 and<unk> 3. Data with native human protein are not currently available.
Zona pellucida
Cave of septum pellucidum
Sinus pericranii
External lamina
Tapetum lucidum
Infundibulum
Germinal matrix
Growth cone