part of part of in taxon results in formation of anatomical entity endocardium morphogenesis anatomical structure formation involved in morphogenesis endocardium formation GO:0060214 Formation of the endocardium of the heart. The endocardium is an anatomical structure comprised of an endothelium and an extracellular matrix that forms the innermost layer of tissue of the heart, and lines the heart chambers. Vertebrata <vertebrates> endocardium