In present opinion, there are at least two independent sites associated with definitive hematopoiesis, those are, yolk sac and para aortic splanchnopleura (PAS)/aorta gonad mesonephros(AGM).

• 目前认为 ,至少有两个独立的部位与永久造血有关 ,即卵黄囊和胚内的PAS/AGM区。