Anatomy
Summary
The superior mesenteric artery (SMA) originates as the second (middle) anterior branch off the aorta around the L1 vertebra level. It is responsible for perfusing the midgut structures, specifically from the third part of the duodenum to the proximal two-thirds of the transverse colon. The SMA also supplies blood to the head of the pancreas via the inferior pancreaticoduodenal artery. The SMA connects with the inferior mesenteric artery (IMA) through the marginal artery of Drummond, and blood is further channeled to the colon wall by vasa recta.
In the event of occlusion in either the SMA or the IMA, collateralization may occur, allowing the unblocked artery to compensate for the obstructed one, perfusing both vascular territories. The blood supply to the colon near the splenic flexure is at risk ischemia during low-flow states, and is referred to as a "watershed" area. Certain conditions are uniquely associated with the SMA: volvulus around the SMA can lead to intestinal malrotation, nutcracker syndrome involves compression of the left renal vein and left gonal vein resulting in left flank pain, hematuria, and varicocele, and SMA syndrome, which involves compression of the third part of the duodenum, leading to symptoms of proximal partial small bowel obstruction like abdominal pain and nausea.
Lesson Outline
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FAQs
The superior mesenteric artery (SMA) is a major artery in the abdominal cavity and is the second (middle) anterior branch off the aorta. The SMA supplies the midgut structures, specifically the 3rd part of the the duodenum to the proximal 2/3s of the transverse colon and the head of the pancreas. The SMA antastamoses with the inferior mesenteric artery via the marginal artery of Drummond, which supplies the colon.
The inferior pancreaticoduodenal artery is a branch of the SMA that branches into the anterior and posterior inferior pancreaticoduodenal arteries, where they travel upward and eventually anastomose with the superior pancreaticoduodenal arteries, which branch off the celiac trunk.
The marginal artery of drummond is a continuous arterial circle along the inner border of the colon. It is comprised of anastomosis of the terminal branches of both the superior and inferior mesenteric arteries, allowing for alternate blood supply routes if either one is obstructed.
A volvulus can cause twisting of the SMA, leading to obstruction of the blood flow which can result in ischemia or necrosis of the small bowel, a life-threatening condition. If not corrected, the affected part of the small bowel may die. Moreover, an obstruction in the small bowel can put pressure on the SMA, potentially leading to Nutcracker Syndrome.
Nutcracker syndrome is a condition where the SMA compresses the left renal vein between the aorta and itself. This compression can result in various symptoms such as hematuria, abdominal pain, and proteinuria. It can also compress the left gonadal vein, leding to varicocele.
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