Foregut to mid-duodenum, midgut to two-thirds of the transverse colon, hindgut to the upper rectum
Expansion
Foregut - oesophagus, stomach, duodenum as far as the ampulla of Vater, plus the liver, gallbladder, pancreas and spleen (the last from mesoderm, but sharing the blood supply)
Midgut - duodenum distal to the ampulla, jejunum, ileum, caecum, appendix, ascending colon, and the proximal two-thirds of the transverse colon
Hindgut - distal third of the transverse colon, descending colon, sigmoid colon, rectum and the upper anal canal
Each segment keeps its own artery, its own venous drainage and its own pattern of referred pain:
- Foregut - coeliac trunk, epigastric pain
- Midgut - superior mesenteric artery, periumbilical pain
- Hindgut - inferior mesenteric artery, suprapubic pain
The watershed at the splenic flexure between the two mesenteric territories is why that region is vulnerable to ischaemic colitis.