What is "hypoblast"

Hypoblast \Hy"po*blast\, n. [Pref. hypo- + -blast.] (Biol.) The inner or lower layer of the blastoderm; -- called also endoderm, entoderm, and sometimes hypoderm. See Illust. of Blastoderm, Delamination, and Ectoderm.

n. (context embryology English) A type of tissue that forms from the inner cell mass and later is incorporated into the endoderm

n. the inner germ layer that develops into the lining of the digestive and respiratory systems [syn: endoderm, entoderm, endoblast, entoblast]

The hypoblast is a tissue type that forms from the inner cell mass. It lies beneath the epiblast and consists of small cuboidal cells.

Extraembryonic endoderm (including Yolk sac) is derived from hypoblast cells. The absence of hypoblast results in multiple primitive streaks in chicken embryos. The formation of the primitive streak, through which gastrulation occurs, is induced by Koller's sickle.