When the sperm meets the egg, this is the reaction which occurs to clear a path through to the egg proper. Enzymes are released from the acrosome of the sperm and these digest a path through.
Search site
ULTIMATE RESULT OF FERTILISATION & IMPLANTATION;
TO
Foetus Image from https://www.flickr.com/photos/lunarcaustic/2128618333/ under creative commons licence
Baby Image from https://www.flickr.com/photos/30945276@N08/2930119674/ under creative commons licence