Zona Pellucida

The layer of the egg cell that prevents the entry of other sperms is called the zona pellucida. It is a thick glycoprotein layer that surrounds the plasma membrane of the oocyte (mature egg cell). The zona pellucida plays a crucial role in the fertilization process by creating a barrier that allows only one sperm to enter and fertilize the egg.

Function of the Zona Pellucida

The zona pellucida performs several important functions in the reproductive process:

1. Preventing polyspermy: Polyspermy refers to the fertilization of an egg by more than one sperm. This can lead to abnormal development and genetic abnormalities. The zona pellucida acts as a physical barrier, ensuring that only one sperm can penetrate and fertilize the egg. Once a sperm penetrates the zona pellucida, it triggers biochemical changes that harden the zona pellucida, preventing the entry of other sperms.

2. Species-specific recognition: The zona pellucida contains species-specific receptors that allow only sperm from the same species to bind to it. This ensures that fertilization occurs between gametes of the same species, preventing cross-species fertilization.

3. Protection: The zona pellucida provides protection to the developing embryo. It forms a protective barrier around the fertilized egg, shielding it from external harmful substances and mechanical damage.

4. Mediating sperm-egg interactions: The zona pellucida plays a role in the initial interactions between the sperm and the egg. It contains sperm-binding proteins that facilitate the binding of the sperm to the zona pellucida, allowing for the process of fertilization to occur.

Conclusion

In conclusion, the zona pellucida is the layer of the egg cell that prevents the entry of other sperms. It acts as a physical barrier, prevents polyspermy, facilitates species-specific recognition, provides protection to the developing embryo, and mediates sperm-egg interactions. Understanding the role of the zona pellucida is crucial in comprehending the process of fertilization and reproductive biology.