2.2心管 1)侧褶:2条心管→1条心管 Neural crest Dorsal aorta Endocardial A myocar Neural crest Intra- embryonic Pericardial Foregut cav Dorsal Fusing mesocardium endocardial heart tubes Epimyocardium Cardiac B Endocardial2.2 心管 1) 侧褶：2 条心管 → 1 条心管