What also happens is calcium ions also flow into our cytoplasm as a result of the opening of those channels, ion channels. And when calcium concentration increases inside the cytoplasm of the cell these granules, these vesicles we call cortical vesicles begin to fuse with the membrane of our excel. And via this exocytosis process the enzymes within these cortical granules are released into the zonapolucida. And what these enzymes do is it essentially reinforces that zonapalucida membrane. It changes the composition of zonapolucida and it forms the fertilization membrane. And this is shown in the following diagram.