develops from develops from immediate transformation of Eumetazoa epithelial tube heart tube embryonic heart tube endocardial tube uberon ZFA:0000360 TAO:0000360 endocardial heart tube AAO:0010411 UBERON:0004141 the paired, longitudinal, endothelial-lined channels formed from the cardiogenic mesoderm in embryonic development; angiogenic cell clusters (aka angioblastic cords) located in a horse-shoe shape configuration in the cardiogenic plate coalesce to form the right and left endocardial heart tubes which then fuse in cephalo-caudal direction to form a single primitive heart tube. EMAPA:32685 NCIT:C34161 XAO:0000337 EFO:0003526 An epithelial tube that will give rise to the mature heart. embryonic tissue primitive heart tube meso-epithelium