Thrombosis of the superior mesenteric artery most directly deprives blood flow to which portion of the small intestine?

• A. Jejunum
• B. Duodenum
• C. Ileum
• D. Cecum

Answer: (A)

The key idea is that the superior mesenteric artery supplies the midgut, which includes the distal duodenum through the ileum. Among the small-bowel regions, the jejunum and ileum receive their blood primarily from SMA branches, whereas the proximal duodenum is supplied mainly by the celiac trunk and only the distal part partly by SMA. Thrombosis of the SMA cuts off the main arterial supply to these midgut portions, so the jejunum—being a primary SMA territory—is most directly deprived. The ileum is also SMA-dependent, but the jejunum is classically the most SMA-dominant segment. The cecum belongs to the large intestine, not the small intestine, and is supplied via SMA as well, but it’s not the focus here.