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endoderm (ĕnˈdədûrmˌ), in biology, inner layer of tissue formed in the gastrula stage of the developing embryo. At the end of the blastula stage, cells of the embryo are arranged in the form of a hollow ball. Cell movement results in an invagination of the bottom region, or vegetal hemisphere, of the embryo so that it resembles a double-walled cup. The inner layer of the cup is the endoderm; the outer layer is the ectoderm; a middle layer, the mesoderm, forms from a marginal zone. The endoderm is the germ layer from which are formed the digestive system, many glands, and part of the respiratory system. See embryo.
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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



(1) The internal layer of the embryo of multicellular animals in the gastrular stage (the internal germ layer). In the process of development, the endoderm forms the wall of the archenteron, which forms the mucosa of the entire intestine and the glands connected with the intestinal tract, including the liver and pancreas. In fishes, the endoderm forms the swim bladder and the internal gills, while in higher vertebrates it forms the lungs. In chordates, the endoderm and organs formed from it exert an inductive influence on the development of the chordamesoderm and on certain body parts formed from the ectoderm, including the mouth, anus, gill slits, and external gills. In turn, the endoderm and organs formed from it typically require interaction with materials originating from the ectoderm and mesoderm.

(2) The internal layer of the body wall in coelenterates.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


The inner, primary germ layer of an animal embryo; sometimes referred to as the hypoblast. Also known as entoderm; hypoblast.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.