Endoderm

(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.