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(embryology) The inner (lower) layer of the embryonic disc, located beneath the epiblast


In mammalian embryogenesis, the blastocyst forms the embryonic disc, which consists of two layers of cells. The upper layer is called the epiblast and the lower layer is called the hypoblast. The cells of the hypoblast are cuboidal in shape in contrast to the columnar shape of the epiblast (particularly the embryonic). In the early embryo development of mammals, the hypoblast cells delaminate from the embryoblast and migrate to form the lining of the blastocyst cavity, where they give rise to the extraembryonic endoderm. Similar to the avian embryos, the hypoblast cells of mammalian embryos do not give rise to any part of the newborn.1 It is the epiblast that gives rise to the three germ layers: endoderm, ectoderm, and mesoderm from which the various organs and parts of the organism develop from through further differentiation.

Word origin: Greek hypo- (under, below) + Greek blastós (germ, sprout)



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1Gilbert SF. Developmental Biology. 6th edition. Sunderland (MA): Sinauer Associates; 2000. Early Mammalian Development. Available from: Link

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embryonic development in a chick

Can anyone please help me out..I just cant understand this gastrulation stage ...my book's too confusing..can't understand how the hypoblast forms the yolk sack? and what exactly are area pelucidia and area opaca? cant understand primitive streak as well as hensen node....arghh...and google ...

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by cracked_doc
Mon Feb 04, 2008 7:40 pm
Forum: Zoology Discussion
Topic: embryonic development in a chick
Replies: 3
Views: 3077

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