Foregut, midgut and hindgut derivatives and their arterial supply
The embryonic gut is split into a head-end foregut, a middle midgut and a tail-end hindgut, and each region keeps its own artery for life.
Remember
In the abdomen, foregut goes with the coeliac trunk, midgut with the superior mesenteric artery and hindgut with the inferior mesenteric artery. The duodenum and the transverse colon each straddle a border between two regions.
In the embryo the gut is a tube lined by endoderm (the innermost early layer of cells, one of three sheets that build the body). This gut tube is divided into three regions, and each region keeps its own artery, so a structure's origin helps you predict its blood supply.
The foregut is the head-end region. It runs from the oesophagus to the duodenum above the ampulla of Vater (the point where the bile duct and the pancreatic duct open into the duodenum), and it also gives the stomach, liver, gallbladder and pancreas. The abdominal foregut is supplied by the coeliac trunk, a short artery from the front of the aorta.
The midgut is the middle region. It begins in the lower duodenum, below the point where the bile duct enters, and continues through the jejunum (the middle part of the small intestine), the ileum (its last part), the caecum (where the appendix arises), the appendix and the ascending colon. Its far end lies in the transverse colon, where the proximal two-thirds belong to the midgut. The superior mesenteric artery supplies it.
The hindgut is the tail-end region. It starts at the distal third of the transverse colon and gives the descending colon (on the left side of the colon), the sigmoid colon (the S-shaped last part of the colon before the rectum), the rectum and the upper anal canal. The inferior mesenteric artery supplies it.
The anal canal has a double origin. The part above the pectinate line (the line where the anal canal changes in origin and lining) is hindgut, whereas the part below it comes from ectoderm (the layer at the surface of the embryo, giving the lower anal canal a skin-like lining), which is distinct from the endoderm that lines the gut tube.
Key facts
- Foregut
- runs from the oesophagus to the duodenum above the opening of the bile duct, and the abdominal foregut is supplied by the coeliac trunk.
- Midgut
- runs from the duodenum below the bile duct entry to the proximal two-thirds of the transverse colon and is supplied by the superior mesenteric artery.
- Hindgut
- runs from the distal third of the transverse colon to the upper anal canal and is supplied by the inferior mesenteric artery.
- Duodenum
- is foregut above the bile duct opening and midgut below it.
- Transverse colon
- has a midgut proximal two-thirds and a hindgut distal third.
- Anal canal
- is hindgut above the pectinate line, while the part below the line comes from ectoderm.
Exam traps
- The duodenum above the bile duct entry is not midgut, because that part is foregut and takes its supply from the coeliac trunk; the midgut part of the duodenum lies below the entry.
- The anal canal below the pectinate line is not hindgut, because that part comes from ectoderm; the hindgut part of the canal lies above the line.
- The proximal two thirds of the transverse colon is not hindgut, because it is midgut supplied by the superior mesenteric artery; the hindgut begins at the distal third.
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