Question

What happens during fertilization in humans after many sperms reach close to the ovum

• A. Cells of corona radiata trap all the sperms except one
• B. Only two sperms nearest the ovum penetrate zona pellucida
• C. Secretions of acrosome helps one sperm enter cytoplasm of ovum through zona pellucida
• D. All sperms except the one nearest to the ovum lose their tails

Answer 1

Answer: (C)

Secretions of acrosome helps one sperm enter cytoplasm of ovum through zona pellucida

Answer 2

The process of fusion of a sperm with an ovum is called fertilization. During fertilization, a sperm comes in contact with the zona pellucida layer of the ovum and induces changes in the membrane that block the entry of additional sperms. Thus, it ensures that only one sperm can fertilize an ovum. The secretions of the acrosome help the sperm enter into the cytoplasm of the ovum through the zona pellucida and the plasma membrane. In contact with the surface of egg covering, the acrosome releases its contained hydrolytic enzymes, also called sperm lysins. It is known as acrosomal reaction. Acrosome reaction results in dissolving of corona cells and degeneration of zona pellucida which helps in sperm penetration.