It is formed by the fusion of the mesodermal layers of two extra-embryonic membranes – the chorion and the allantois.

The first is the chorionic epithelium that is the external layer present immediately below the shell membrane.

[4] The chorionic epithelial layer contains the calcium transporting region of the CAM, and thus is responsible for the transport of calcium ions from the egg shell into the embryo for the purpose of ossification of the bones of the developing embryo.

Development of the allantois occurs extra embryonically from the ventral wall of the endodermal hindgut.

A small hole is made on the side of the air chamber to equilibrate the pressure, followed by the cracking of the egg on a petri-dish.

There are also problems associated with the handling of the embryo, as the yolk membrane is prone to rupture both during and after the culture.

In this method, fertilized eggs are rotated inside an incubator for three days in order to prevent the embryo from sticking to the membranes of the shell.

It is easier to maintain sterility as well the integrity of the CAM and the embryo when they are present inside the shell.