Superior mesenteric artery
Branch · L1 Midgut 5 branches
Arises from the front of the aorta at L1, about 1 cm below the coeliac trunk, behind the neck of the pancreas and splenic vein, then passes forward over the left renal vein, uncinate process and third part of the duodenum into the root of the mesentery. Supplies the midgut: duodenum distal to the major papilla, jejunum, ileum, caecum, appendix, ascending colon and proximal two-thirds of the transverse colon.
Traced from the start
- Abdominal aorta
- Superior mesenteric artery
Detail
- Level
- L1
- Branches
- Inferior pancreaticoduodenal, 12–15 jejunal and ileal, ileocolic, right colic, middle colic
- Relations
- Left renal vein and third part of the duodenum lie in the angle between SMA and aorta; superior mesenteric vein on its right
When it goes wrong
Embolus from atrial fibrillation or a mural thrombus lodging in the SMA, usually just beyond the middle colic origin
Acute mesenteric ischaemia: severe abdominal pain out of proportion to examination, later bloody diarrhoea, raised lactate and metabolic acidosis; proximal jejunum and transverse colon are spared when the embolus sits distal to the first branches
Loss of the retroperitoneal fat pad (rapid weight loss, anorexia, prolonged bed rest, scoliosis surgery) narrows the aortomesenteric angle below about 25 degrees
SMA syndrome: the third part of the duodenum is pinched between SMA and aorta, giving post-prandial bilious vomiting and proximal duodenal dilatation; the left renal vein can be trapped in the same angle (nutcracker syndrome: left-sided haematuria and varicocele)
Atherosclerotic stenosis of two or more of coeliac, SMA and IMA
Chronic mesenteric ischaemia: post-prandial pain ('intestinal angina'), fear of food and weight loss
Practise this structure
1 question in the bank tagged Mesenteric Arterial Supply.