Question

The membrane cover of follicular cells around the ovum of ovulation is
A. Corona radiata
B. Zona radiata
C. Zona pellucida
D. Chorion

Answer 1

It is the membranous cover of follicular cells ovum of ovulation. This is the transparent layer that is present around the ovum before implantation. It mostly protects the ovum that is present within each ovary. It is an important structure for the ovum before and also after fertilization.

Complete answer:
The Zona pellucida is also called an egg coat or it is a glycoprotein layer that surrounds the plasma membrane of the mammalian oocytes. It plays a vital part of the oocyte. This zona pellucida first appears in unilaminar primary oocytes. The zona pellucida is circled by the corona radiata. This corona radiata is composed of cells that care for the egg when it is emitted from the ovary.The zona pellucida appears as a thick clear girdle that is surrounded by the cells of the corona radiata.

The structure of this zona pellucida is a translucent matrix of the glycoprotein that surrounds the mammalian oocyte and its formation is critical to a successful fertilization. In the non- mammals creature it is called the vitelline membrane. The function of the zona pellucida is the thick membrane and it allows the species to a specific fertilization that to prevent the polyspermy then it enables the acrosome reaction for successful adhesion and then it penetrates the sperm cell. The major parts of glycoprotein of the egg coat are responsible and are known as sperm binding proteins.

Hence, the correct answer is option (C).

Additional information:

Corona radiata: Basically this corona radiata is the outer layer follicular cell.
Zona radiata: This zona radiata is an inner surface that regulates transition in the follicle cell.
Chorion: This chorion is the double layered membrane that is formed by the embryonic mesoderm.

Note: In humans it is five days after the fertilization, the blastocyst that performs zona hatching, degenerates and then decomposes to be replaced by the underlying layer of the trophoblastic cells. This zona pellucida is very essential for the oocyte growth and also fertilization. Basically the successful fertilization depends on the ability of the sperm to penetrate the extracellular of the zona pellucida surrounding the egg.