Changes of the zona pellucida patterns during oocyte maturation, fertilization and embryo development in mammals: mini-review

The mammalian zona pellucida (ZP) is an extracellular matrix that surrounds immature and mature oocytes and early embryos until the stage of a blastocyst and its implantation. This mini-review summarizes basic information on the ZP and its morphologic and functional changes during in vitro oocyte maturation and fertilization and in vivo pre-implantation embryo development.