Figure 1 - Primordial gut.

a: Lateral view of a 4-week embryo showing the relationship of primordial gut to yolk sac. b: Drawing of median section of the embryo showing the early digestive system and its blood supply. The primordial gut is a long tube extending the length of the embryo. Its blood vessels are derived from the vessels that supplied the yolk sac. (Source: Moore KL, Persaud TVN. The Developing Human, 7th ed. Philadelphia: Elsevier, Inc., 2003:256).