Zona pellucida

(Latin, zona pellucida = transparent zone) A specialized extracellular matrix surrounding the developing oocyte (egg, ovum) within each follicle within the ovary. This thick matrix is thought to be formed by secretions from the oocyte and the follicle granulosa cells and consists of three types of zona pellucida glycoproteins Z#ZP1 ZP1, Z#ZP2 ZP2 and Z#ZP3 ZP3 which have different roles in fertilization.

Following fertilization, the zona pellucida also surrounds the blastocyst during the first week of development, from which it "hatches".

The zona pellucida has a role in fertilization, sperm binding, preventing polyspermy, blastocyst development and preventing premature implantation (ectopic pregnancy).

Links: Carnegie stage 3

UNSW Embryology Links: Week 1 - Fertilization | Week 1 - Oogenesis |