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A B C D E F G H I K L M N O P R S T U V W Y Z

Hatching of the zona pellucida from the outside of the blastocyst must occur before implantation in the uterine wall is possible. Assisted zona hatching (AZH) is also used as an assisted reproductive technology to further increase the chances of implantation in the uterus.

The zona pellucida is a membrane composed of four glycoproteins (ZP1-4) that surrounds the plasma membrane of the mammalian oocyte. It is important for inducing the acrosome reaction during fertilization and preventing polyspermy. The zona pellucida persists through pre-implantation embryo development, but the blastocyst must hatch out of the zona pellucida in order to undergo implantation in the uterus.

A zygote is the diploid cell that is produced following fertilization of the female egg by the male sperm. In contrast to a zygote, which is unicellular, an embryo has begun to undergo cell divisions and is multicellular.