The primitive gut is a derivative of

With the formation of the head and tail folds, pas of the yolk sac become enclosed within the embryo. In this way, a tube lined by endoderm is formed in the embryo. This is the primitive gut, from which most of the gastrointestinal tract is derived. The primitive gut is in free communication with the rest of the yolk sac. The pa of the gut cranial to this communication is the foregut; the pa caudal to the communication is the hindgut, while the intervening pa is the midgut. Ref:Inderbir Singh's Human Embryology, eleventh edition, pg.no., 172.