Epiblast

Epiblast is a layer of cells in the embryo that is formed after fertilization and cell division. It is one of the two layers that make up the blastocyst, the other being the hypoblast. The epiblast is the source of all three germ layers in the developing embryo, which give rise to all the tissues and organs of the body.

Formation

The epiblast forms during the second week of embryonic development, after the zygote has undergone several rounds of cell division to form a hollow sphere of cells known as the blastocyst. The blastocyst consists of an outer layer of cells, the trophoblast, and an inner cell mass. The inner cell mass differentiates into two layers: the epiblast and the hypoblast. The space between these two layers is known as the amniotic cavity.

Function

The epiblast is responsible for the formation of the three germ layers in the developing embryo: the ectoderm, mesoderm, and endoderm. This process, known as gastrulation, begins with the formation of the primitive streak in the epiblast. Cells from the epiblast migrate through the primitive streak to form the mesoderm and endoderm, while cells that remain in the epiblast form the ectoderm.

Clinical Significance

Abnormalities in the formation or function of the epiblast can lead to a variety of congenital anomalies. For example, failure of the epiblast to properly form the germ layers can result in birth defects affecting the heart, lungs, and other organs. Research into the epiblast and its role in embryonic development is therefore crucial for understanding and preventing these conditions.

See Also

• Blastocyst
• Embryonic development
• Gastrulation
• Primitive streak

Epiblast

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  Human embryo at day 9
• Migration of epiblast cells in the mammalian embryo
  Migration of epiblast cells in the mammalian embryo