Superior Mesenteric Artery

Supplies gut from entrance of Bile Duct to a level just short of the Splenic Flexure of the Colon
Arises from the front of the Aorta 1cm below the Coeliac Trunk - At level of L1 vertebra
Course:
- Directed steeply downwards behind the Splenic Vein and Body of Pancreas
- Superior Mesenteric Vein on the right side
- Enters upper end of Small Bowel Mesentery
- Passes down to the right along the Root of the Mesentery
- NB: Terminates in the Terminal Ileum at the apex of the loop of the midgut (site of attachment of the Vitello-Intestinal Duct) – approximately 60cm proximal to the caecum
Relations:
- Posterior: (in order from superior to inferior)
  - Left Renal Vein
  - Uncinate Process of the Pancreas
  - 3rd Part of the Duodenum
Branches:
- Inferior Pancreaticoduodenal Artery
- Jejunal Branches
- Ileal Branches
- Ileocolic Artery
- Right Colic Artery
- Middle Colic Artery

Arises from posterior surface of Superior Mesenteric Artery
Variation: May come off 1st Jejunal Branch
Divides into anterior and posterior branches – run in the curve between the Duodenum and the Head of the Pancreas
Supplies Duodenum and Head of Pancreas
Anastomose with the terminal branches of the Superior Pancreaticoduodenal Artery

Arises from the left of the main trunk of the Superior Mesenteric Artery as it passes down between the two layers of the Mesentery

Arises from the right side of the Superior Mesenteric Artery low down in the base of the Mesentery
Descends to the right iliac fossa and divides into superior and inferior branches
- Superior branch – Runs up along the left side of the Ascending Colon to anastomose with the Right Colic Artery
- Inferior branch – Runs to the ileocolic junction and gives off Anterior and Posterior Caecal Arteries, an Appendicular Artery, and an Ileal Branch which ascends to the left on the ileum to anastomose with the terminal branch of the Superior Mesenteric Artery

Arises from the right side of the Superior Mesenteric Artery or in common with the Ileocolic Artery
Runs across the Right Psoas Muscle, Gonadal vessels, Ureter and Genitofemoral Nerve, and Quadratus Lumborum, just behind the peritoneal floor of the Right Infracolic compartment
Divides near the left side of the Ascending Colon into two branches
- Descending branch – runs down to anastomose with the Superior Branch of the Ileocolic Artery
- Ascending branch – runs up across the inferior pole of the Right Kidney to the Hepatic Flexure where it anastomoses with a branch of the Middle Colic Artery
Anatomical Variation: [3]
- Right Colic Artery present in only 10-63% of cases
- Right Colic Artery may arise from the Ileocolic Artery or the Middle Colic Artery

Arises from the right side of the Superior Mesenteric Artery, as it emerges at the lower border of the Neck of the Pancreas
Descends between the two leaves of the Transverse Mesocolon
Lies to the right of the midline
At the intestinal border of the Transverse Mesocolon, it divides into right and left branches
- Right branch – anastomoses with the ascending branch of the Right Colic Artery
- Left branch – supplies the Transverse Colon almost to the Splenic Flexure where it anastomoses with a branch of the Left Colic Artery
Anatomical Variation: [3]
- Branches of the Middle Colic Artery mostly arise from the main trunk (64%)
- One or two arterial branches may originate directly from the Superior Mesenteric Artery in 32% and 3.3% of cases, respectively
- Multiple Middle Colic Arteries (2 or 3 branches) could arise directly from the Superior Mesenteric Artery (7.2%)

Venous Drainage

Venous Drainage of Midgut

Each branch of the Superior Mesenteric Artery is accompanied by a vein
All these veins flow into the Superior Mesenteric Vein
- Lies to the right of the artery
- Crosses the 3rd part of the Duodenum and Uncinate Process of the Pancreas
- Joined by the Splenic Vein behind the Neck of the Pancreas to form the Portal Vein
- Portal vein continues upwards behind the 1st part of the Duodenum