. . "zona pellucida"@en-us . "105608615"^^ . . . . . "105288393"@en-us . "0"^^ . "05608615-n"^^ . . . . "thick membrane around the mammalian ovum; can be penetrated by one sperm in the fertilization process; usually remains around the fertilized egg until it is implanted in the wall of the uterus"@en-us . . "0"^^ . "zona pellucida"^^ . .