The strong membrane that forms around an ovum as it develops in the ovary. The membrane remains in place during the egg's travel through the fallopian tube. To fertilize the egg, a sperm must penetrate the thinning zona pellucida. If fertilization takes place, the zona pellucida disappears, to permit implantation in the uterus.

Thick, transparent noncellular layer or envelope of uniform thickness surrounding an oocyte (a developing egg cell); the outer wall of an ovum.

The zona pellucida forms the outside covering of the oocyte (egg). The binding of sperm to this layer is one of the early events that leads to fertilisation.

A tough transparent Membrane surrounding the Ovum. It is penetrated by the Sperm during Fertilization.

A tough transparent membrane surrounding the OVUM. It is penetrated by the sperm during FERTILIZATION.

 the protective surface layer of the egg.

a thick extracellular matrix surrounding the mammalian ovum (egg) which binds sperm and initiates the acrosome reaction of the sperm.

The outer ‘shell' surrounding the egg. The Zona Pellucida serves two purposes; firstly allowing only one sperm to enter the egg for fertilization and secondly to hold the cells of the developing [..]

The outer protective coat of the egg