Bilaminar embryonic disc

Bilaminar embryonic disc is a structure formed in the embryo in the first two weeks after fertilization. It is a circular plate of bilayer cells. The bilaminar embryonic disc is composed of two layers: the epiblast and the hypoblast.

Formation

The formation of the bilaminar embryonic disc is a part of the process of gastrulation. After the fertilization of the ovum by the sperm, the resulting zygote begins to divide and form a blastocyst. The blastocyst implants itself into the endometrium of the uterus. The cells of the blastocyst differentiate into an inner cell mass and an outer cell mass. The inner cell mass forms the embryo, while the outer cell mass forms the placenta. The inner cell mass further differentiates into the epiblast and the hypoblast, forming the bilaminar embryonic disc.

Structure

The bilaminar embryonic disc consists of two layers of cells. The upper layer, or the epiblast, is composed of columnar cells, while the lower layer, or the hypoblast, is composed of cuboidal cells. The epiblast is closer to the amniotic cavity, while the hypoblast is closer to the yolk sac. The space between the epiblast and the hypoblast is known as the primitive streak.

Function

The bilaminar embryonic disc is crucial in the development of the embryo. It forms the basis for the structure of the embryo and is involved in the formation of the germ layers: the ectoderm, the mesoderm, and the endoderm. These germ layers further differentiate to form all the tissues and organs of the body.

Clinical Significance

Abnormalities in the formation of the bilaminar embryonic disc can lead to developmental disorders. For example, failure of the bilaminar disc to form properly can result in congenital malformations.

See Also

• Gastrulation
• Embryogenesis
• Blastocyst
• Germ layers