Entry of sperm cells in egg cell
Let me explain you step by step :
Firstly , Sperm passes through corona radiata.
Then, the reaction of acrosome takes place.
The ZP3 , which is a glycoprotein of zona pellucida binds with sperm head and releases its hydrolytic enzymes .
Sperm passes through pellucida and reaches and reaches oolemma.
Then, the fusion of plasma membrane of egg and sperm takes place enabling the sperm content to enter egg .
The zona pellucida gets harden by cortical reaction .