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Term
Zona Pellucida
What Is
Zona Pellucida?
The zona pellucida is a protein membrane shell that coats an egg as it develops in the ovary. The shell helps to regulate fertilization and remains in place until implantation.
To facilitate successful conception, the shell must be the appropriate thickness, allowing sperm to permeate the casing, and for the embryo to "hatch" from the shell at the time of implantation.