What is the Difference Between Epiblast and Hypoblast?

The epiblast and hypoblast are two distinct cell layers that arise from the inner cell mass in the mammalian blastocyst during early embryonic development. They form the bilaminar embryonic disc, which is a flat slice across the developing sphere and splits the environment into two cavities. The key differences between the epiblast and hypoblast are:

1. Formation: Epiblast forms three germ layers (ectoderm, mesoderm, and endoderm) and the amnion, while hypoblast forms the yolk sac.
2. Anatomical location: Epiblast is the upper layer and forms a semisphere known as the amniotic cavity, while hypoblast is the lower layer and surrounds the yolk sac.
3. Cell structure: Epiblast cells are columnar cells, while hypoblast cells are cuboidal cells.

During gastrulation, the embryo undergoes differentiation into the three primary germ layers (ectoderm, mesoderm, and endoderm) through the epiblast. The hypoblast, on the other hand, does not contribute to the embryo and forms the yolk sac. The bilaminar embryonic disc, which consists of the epiblast and hypoblast, is established prior to implantation and gastrulation.

Comparative Table: Epiblast vs Hypoblast

Here is a table comparing the differences between the epiblast and hypoblast:

The epiblast and hypoblast are both derived from the inner cell mass of the blastocyst and are crucial for the development of the embryo. The epiblast develops into the three primary germ layers, while the hypoblast develops into the yolk sac.