As soon as the spermatozoon fuses with the ovum, signal transduction occurs, resulting in an increase of cytoplasmic calcium ions.
The vitelline membrane of the hen is made of two main protein layers that provide support for the yolk and separation from the albumen.
[2] Taking a wider view, ZP domain proteins are found in the vitelline membrane of chordates (which contains the vertebrates) in general.
[3] The vitelline membrane is known to function as a barrier that allows for diffusion of water and selective nutrients between the albumen and the yolk.
[3] In the adult hen, liver cells express the proteins required for initial formation of the inner layer.
After ovulation, fertilization of the egg proceeds with the formation of the outer layer that is secreted by infundibulum glands located along the first parts of the oviduct.
In the chicken egg, the yolk is separated from the albumen by the vitelline membrane which acts as a barrier to microbial infection.
[7] A recent study reports that VMO 1 can be a potential diagnostic marker for ovarian cancer in hens due to its ability to regulate estrogen and target microRNAs in the chickens' oviduct.