The ductus carotis arteriosus and ductus botalli are still present and link up the arterial arches separately . there are two aa . gastrica , one coming from aorta dorsalis directed branch , the other coming from a . gastrolinealis which branch of aa 2 .動脈系統:頸動脈導管、波氏導管依然存在;胃動脈有兩個來源:背主動脈的直接分支,腸系膜動脈的胃脾分支;肝動脈為來自腹腔腸系膜動脈的一級分支。