2)头褶:心管→围心腔背侧 口咽膜尾侧 Pericardial Amnion Connecting Cardiogenic cavity Neural plate stalk area Allanton AT Prochordal Notochord plate Amniotic Cloacal membrane cavity Foregut A1B1 Hindgut tube B Heart tube Buccopharyngeal Pericardial Dorsal B1 membrane cavity mesocardium Cloaca Pericardial Cloacal membrane2) 头褶：心管→ 围心腔背侧 ↘口咽膜尾侧