Arterial supply of the gut (foregut, midgut, hindgut)

Also known as: splanchnic circulation, foregut midgut hindgut, mesenteric circulation, portosystemic anastomoses

Three unpaired branches of the abdominal aorta each supply one embryological region of the gut: the coeliac trunk (foregut), the superior mesenteric artery (midgut) and the inferior mesenteric artery (hindgut). Venous blood returns through the hepatic portal vein.

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Overview

The coeliac trunk (T12) supplies the foregut, from the abdominal oesophagus to the 2nd part of the duodenum (to the major papilla). It also supplies the liver, gallbladder, upper pancreas and spleen; the spleen is mesodermal but develops in the dorsal mesogastrium. Its three branches are the left gastric (to the oesophagus and lesser curvature), the splenic (short gastrics, left gastro-omental, pancreatic branches) and the common hepatic. The common hepatic gives the gastroduodenal artery (right gastro-omental, superior pancreaticoduodenal) and the hepatic artery proper (right gastric, right and left hepatic; the cystic artery comes from the right hepatic).

The superior mesenteric artery (L1) supplies the midgut, from the major papilla to the proximal two-thirds of the transverse colon. Its branches are the inferior pancreaticoduodenal artery, jejunal and ileal arteries (arcades → vasa recta), and the middle colic, right colic and ileocolic arteries (with the appendicular artery). It arises behind the neck of the pancreas and passes in front of the left renal vein and the 3rd part of the duodenum.

The inferior mesenteric artery (L3) supplies the hindgut, from the distal third of the transverse colon to the pectinate line. Its branches are the left colic, the sigmoid arteries and the superior rectal artery.

Collateral pathways connect the territories. The pancreaticoduodenal arcades link coeliac and SMA. The marginal artery (of Drummond) and the inconstant arc of Riolan link SMA and IMA. The rectal anastomoses link IMA and internal iliac. Venous blood follows the arteries into the superior and inferior mesenteric and splenic veins, which form the hepatic portal vein behind the neck of the pancreas.

Location: Anterior surface of the abdominal aorta: coeliac trunk at T12, SMA at L1, IMA at L3.

Parts & subdivisions

Coeliac trunk → foregut
Left gastric, splenic and common hepatic arteries. Referred pain to the epigastrium. Sympathetic: greater splanchnic nerves (T5–T9). Parasympathetic: vagus.
Superior mesenteric artery → midgut
Inferior pancreaticoduodenal, jejunal, ileal, ileocolic, right colic and middle colic arteries. Referred pain to the umbilical region. Sympathetic: lesser splanchnic nerves (T10–T11). Parasympathetic: vagus.
Inferior mesenteric artery → hindgut
Left colic, sigmoid and superior rectal arteries. Referred pain to the hypogastrium. Sympathetic: lumbar splanchnic nerves (L1–L2). Parasympathetic: pelvic splanchnic nerves (S2–S4).
Hepatic portal vein
Formed by the SMV and splenic vein (which usually receives the IMV) behind the neck of the pancreas. About 8 cm long; carries about 75% of hepatic inflow.
Portosystemic anastomoses
Oesophageal: left gastric ↔ azygos (varices). Anorectal: superior rectal ↔ middle and inferior rectal (rectal varices). Paraumbilical: paraumbilical veins ↔ superficial epigastric veins (caput medusae). Retroperitoneal: colic and splenic tributaries ↔ renal, lumbar and gonadal veins.

Anatomy

Venous drainage: Superior mesenteric, inferior mesenteric and splenic veins → hepatic portal vein → liver sinusoids → hepatic veins → IVC.
Lymphatic drainage: Pre-aortic nodes named after the arteries (coeliac, superior mesenteric, inferior mesenteric) → intestinal trunks → cisterna chyli.
Branches: Coeliac trunk: left gastric, splenic, common hepatic. SMA: inferior pancreaticoduodenal, jejunal and ileal, middle colic, right colic, ileocolic. IMA: left colic, sigmoid, superior rectal.
Development: The three arteries are persisting ventral (vitelline) branches of the dorsal aorta that supplied the yolk sac. Each became tied to one gut segment, which is why embryological origin predicts both arterial supply and the site of referred pain.

Function

Delivers about 25% of resting cardiac output to the digestive organs, rising substantially after meals (postprandial hyperaemia).
Routes absorbed nutrients through the liver before they reach the systemic circulation (first-pass metabolism).

Clinical significance

Acute mesenteric ischaemia

Caused by embolism to the SMA (atrial fibrillation), thrombosis on atheroma, mesenteric venous thrombosis or non-occlusive low flow. It produces severe pain out of proportion to the signs, lactic acidosis and then peritonitis, and needs urgent CT angiography and revascularisation or resection.

Chronic mesenteric ischaemia ("intestinal angina")

Atherosclerotic narrowing of at least two of the three arteries causes post-prandial pain, fear of eating and weight loss.

Watershed areas

The splenic flexure (Griffiths point, between SMA and IMA) and the rectosigmoid (Sudeck point) are vulnerable to ischaemic colitis during hypotension or after IMA ligation in aortic surgery.

Mnemonics

Levels: 12-1-3

Coeliac T12, SMA L1, IMA L3. Foregut, midgut, hindgut; epigastric, umbilical, suprapubic pain.

Compiled from standard anatomy and physiology references — see the Digestive System sources. For education only; not medical advice.