What is corona radiata and zona pellucida in an ova ?

Zona pellucida is the glycoprotein membrane present around an ovum as it develops in the ovary. The membrane remains in place during the egg's travels through the Fallopian tube.

It binds spermatozoa, and is required to initiate the acrosome reaction. To fertilize the egg, a sperm must penetrate the thinning zona pellucida. If fertilization takes place, the membrane disappears to permit implantation in the uterus

 

The zona pellicuda is surrounded by an outer envelope, the corona radiata, which is many cell layers thick and formed by follicle cells adhering to the oocyte before it leaves the ovarian follicle.  They appear at ovulation, but may disappear eventually after fertilization