Embryonic Disk

Last updated: May 5th, 2025

The embryonic disc (or embryonic disk) results from the flattening of the embryoblast. It consists of two layers; an upper ectoderm which is closer to the amniotic cavity, and a lower endoderm which is near the blastocyst cavity. A short time later, a third layer called the mesoderm forms between the endoderm and ectoderm. These three layers are called the primary germ layers.