Final answer:
The superior mesenteric artery is most likely to get constricted by a volvulus of the small bowel between the third and fourth segments of the duodenum.
Step-by-step explanation:
Between the third and fourth segments of the duodenum, the blood vessel most likely to get constricted by a volvulus of the small bowel is the superior mesenteric artery.
The superior mesenteric artery is the main arterial supply to the small intestine, providing blood rich in nutrients. It runs parallel to the veins and drains into the superior mesenteric vein, which carries the nutrient-rich blood to the liver via the hepatic portal vein.
A volvulus is a condition where a loop of intestine twists around itself, leading to restricted blood flow and potentially serious complications. In this case, the twist between the third and fourth segments of the duodenum can result in the constriction of the superior mesenteric artery and impede blood flow.