endoderm /en″dədurm/ [Gk, endon + derma, skin] , (in embryology) the innermost of the cell layers that develop from the embryonic disk of the inner cell mass of the blastocyst. From the endoderm arises the epithelium of the trachea, bronchi, lungs, GI tract, liver, pancreas, urinary bladder, anal canal, pharynx, thyroid, tympanic cavity, tonsils, and parathyroid glands. The endoderm thus comprises the lining of the cavities and passages of the body and the covering of most of the internal organs. Compare ectoderm, hypoblast, mesoderm.
