Thick membrane enclosing the mammalian ovum; it can be penetrated by one sperm in the fertilization process, and usually remains around the fertilized egg until its implantation in the wall of the uterus.
The thick membrane that develops around the mammalian oocyte within the ovarian follicle. It is penetrated by at least one spermatozoon at fertilization and persists around the ‘blastocyst until it reaches the womb.
The inner, solid, thick, membranous envelope of the ovum. It is pierced by many radiating canals, giving it a striated appearance.
The dense, clear, acellular barrier enveloping a maturing egg cell inside the ovarian follicle. During fertilization, the zona pellucida is breached by at least one sperm.