Prerequisites for the penetration of sperm into ovum are

The process of fusion of a sperm with an ovum is called fertilisation. Capacitation is a process, in which the sperm undergoes a series of cellular changes that enables its participation in fertilization. It occurs in female reproductive tract. A fundamental change that occurs during capacitation is alkalization of sperm cytoplasm, in which the intracellular pH levels increase, particularly in the flagellum. Important change in capacitation is the removal of glycoproteins and cholesterol from the plasma membrane.The secretions of the acrosome help the sperm enter into the cytoplasm of the ovum through the zona pellucida and the plasma membrane, which is called acrosomal reaction.Cortical reaction and formation of fertilisation membrane will not allow penetration of sperm (block to polyspermy).