Gastrulation in chick?

Gastrulation is a crucial process in embryonic development that occurs in various animal species, including chicks. It is the process by which the three primary germ layers (ectoderm, mesoderm, and endoderm) are formed, which will give rise to different tissues and organs in the developing embryo.

In chicks, gastrulation begins around the 14th hour of incubation. The process starts with the formation of the primitive streak, a thickened band of cells that appears on the surface of the blastoderm (a disc-shaped structure formed by the blastula stage). The primitive streak extends from the posterior end towards the anterior end of the embryo.

As gastrulation progresses, cells from the epiblast (a layer of cells on the upper surface of the blastoderm) migrate towards the primitive streak and move inward through a process called invagination. These migrating cells form the mesoderm and endoderm germ layers.

The cells that move through the primitive streak and settle between the epiblast and hypoblast (the lower layer of cells in the blastoderm) form the mesoderm. The mesoderm will give rise to various structures, including the notochord, somites (which will develop into muscles and vertebrae), and the circulatory system.

The cells that continue to move through the primitive streak and displace the hypoblast cells form the endoderm. The endoderm will give rise to the lining of the digestive tract, respiratory system, liver, and pancreas.

Meanwhile, the remaining cells in the epiblast form the ectoderm, which will give rise to the nervous system, skin, and other external structures.

Overall, gastrulation in chicks is a complex process that involves the formation and migration of different cell types to establish the three primary germ layers, which will eventually differentiate into the various tissues and organs of the developing chick embryo.