Question

What is the function of zona pellucida?

Answer 1

Zona pellucida is made by the glycoprotein. It first appears at the unilaminar primary oocyte. It enables the acrosome reaction. It is the layer of ovule so it is important in the reproduction process. It produces perfect penetration and adhesion to the sperm.

Complete answer:
Zona pellucida is the thick transparent membrane and it is surrounded by the mammalian ovum before implantation.
It prevents polyspermy. Acrosome reaction is enabled by zona pellucida to produce the comfortness for the sperm. It produces the acrosome reaction by binding with the capacitated sperms. Zona pellucida communicates with the follicle cells oocyte during oogenesis.
It is used to protect the eggs, oocytes and embryos during the development process. It regulates and provides interaction between ovulated eggs and free sperm during fertilization. It prevents sperm from binding to fertilized eggs. It also prevents implantation in the fallopian tube.
Zona pellucida is secreted by the oocyte and ovarian follicles. It is surrounded by the corona radiata. This corona is composed of cells which take care of the egg when it is emitted from the ovary. It prevents premature implantation or ectopic pregnancy. It is used to develop the blastocyst.

Note:
It protects the embryo before fertilization. It acts as the species specific barrier to sperm binding and penetration. It is the blockade of hetero specific fertilization. There are three glycoproteins used in the ZP. They are ZP$1$, ZP$2$ and ZP$3$. ZP$3$ mediates the sperm specific egg binding during fertilization. ZP$2$ mediates subsequent sperm binding during ovulation. ZP$1$ acts as the protein mesh work cross-linked with ZP$2$ and ZP$1$.