Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
The epiblast is a layer of cells derived from the inner cell mass of the blastocyst, which ultimately gives rise to all the tissues and organs of the embryo. It is positioned above the hypoblast in early embryonic development.
A structure formed in the early development of mammals, consisting of an inner cell mass, an internal cavity, and an outer layer known as the trophoblast.
A phase early in the embryonic development of most animals, during which the single-layered blastula is reorganized into a multilayered structure known as the gastrula.
Hypoblast: The layer of cells that forms beneath the epiblast in an early embryo and contributes mainly to extraembryonic structures rather than to the embryo itself