What is ovum activation?

Cortical Reaction (Activation of Ovum):

1. Immediately after penetration of a spermatozoon into the egg, the cortical reaction initiates to prevent further entry of spermatozoa.
2. Chemical substances found in the cortical granules are released in between the plasma membrane and the vitelline membrane.
3. These substances fuse with the vitelline membrane to form the fertilization membrane.
4. Following metabolic activities are initiated in the ovum after penetration of sperm:

• Fertilization cone is formed on the egg surface.
• Fertilization membrane is formed by the vitelline membrane and cortical granules.
• Permeability of the plasma membrane is increased.
• Rate of protein synthesis is increased.
• Mitotic divisions start in the fertilized egg.