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Development of the gut begins with the appearance of the secondary yolk sac which is lined by endoderm following gastrulation. Cephalocaudal and lateral folding of the embryo during the 4th week creates an elongated tube lined with endoderm and which is narrowly connected to the yolk sac by the yolk stalk. This primitive gut tube is divided into three regions: foregut, midgut, and hindgut. It is also attached to the posterior body wall by a double sheet of mesoderm called the dorsal mesentery. Additionally, the foregut region is attached to the anterior body wall by a ventral mesentery. Each of the three subdivisions of the gut tube give rise to specific organs and parts of the gastrointestinal tract.
  • Foregut - esophagus, stomach, proximal duodenum, liver, gallbladder and pancreas
  • Midgut - distal duodenum, jejuneum, ileum, cecum, appendix and proximal colon
  • Hindgut - distal colon, rectum, anal canal and anus
Each division of the embryonic gut has blood supply from a specific unpaired branch of the abdominal aorta.