In amniote animal embryology, the epiblast is a tissue type derived either from the inner cell mass in mammals or the blastodisc in birds and reptiles. 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 in a process called gastrulation[WP]. The outer of the two layers of the blastoderm that form during gastrulation, corresponding to primitive ectoderm during gastrulation and to the definitive ectoderm after gastrulation[ZFA] [ ]

Synonyms: epiblast

This is just here as a test because I lose it

Term information


uberon_slim, vertebrate_core, grouping_class, early_development

depicted by

editor note

MP says - tissue that gives rise to the ectoderm, endoderm and mesoderm of the embryo proper. In HOG, epiblast is part of primitive streak/blastpore, which is inconsistent with the MP definition of primitive streak as a ridge of the epiblast. Note that these terms, epiblast and hypoblast, are also used to describe layers of the avian embryonic blastoderm, but the layers so-named seem to be altogether different in these two kinds of vertebrate embryos(CVS). Consider obsoleting this as a grouping class

has related synonym

primitive ectoderm

homology notes

In pregastrula zebrafish embryos, the epiblast is an inverted cup of cells that sits on top of a large yolk cell. (...) In amniote embryos (mammals and birds), gastrulation initiates in an epithelial layer called the epiblast. Cells in the epiblast undergo an epithelial to mesenchymal transition (EMT), migrate through the primitive streak (PS), and incorporate in the middle (mesoderm) or outer (endoderm) layer. The presumptive definitive endoderm (DE) cells invade and displace an outer layer of extraembryonic tissue cells, the hypoblast in chick and the visceral endoderm (VE) in mouse, which form supporting structures such as the yolk sac.[uncertain][VHOG]