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Section through the embryo. (Epiblast visible but not labeled.)
Latin epiblastus
Carnegie stage 3
Days 8
Precursor inner cell mass
Gives rise to ectoderm, mesoderm, endoderm
Code TE E5.
Anatomical terminology

In amniote animal embryology, the epiblast is a tissue type derived either from the blastodisc in reptiles (incl. birds) or the inner cell mass of the blastocyst in mammals. It lies above the hypoblast.


In mammalian embryogenesis, the columnar cells of the epiblast are adjacent to the trophoblast, while the cuboidal cells of the hypoblast are closer to the blastocoele. The epiblast, whilst referred to as the primary ectoderm, differentiates to form all three layers of the trilaminar germ disc (ectoderm, mesoderm, and endoderm) in a process called gastrulation.


Gastrulation occurs in the epiblast of avian embryos. A local thickening of the epiblast, known as Koller's sickle, is key in inducing the primitive streak, the structure through which gastrulation occurs.[1]

Epiblast diversity[edit]

Human epiblast is disc-shaped as opposed to the mouse epiblast which is cup-shaped.

See also[edit]


  1. ^ Gilbert SF. Developmental Biology. 10th edition. Sunderland (MA): Sinauer Associates; 2014. Early Development in Birds. Print

External links[edit]