What vessel drains the spleen into the inferior vena cava?

The splenic vein is the correct answer because it plays a direct role in draining the blood from the spleen. The splenic vein collects deoxygenated blood and carries it away from the spleen, eventually merging with the superior mesenteric vein to form the portal vein, which transports blood to the liver. However, it is important to note that the splenic vein itself does not drain directly into the inferior vena cava.

In the context of the inferior vena cava, the focus is often on systemic circulation rather than the portal circulation involving the liver. Blood from the splenic vein ultimately makes its way to the inferior vena cava through a series of veins, including the superior mesenteric vein joining it to form the portal vein first, and then the portal blood eventually returns to the systemic circulation via the hepatic veins draining into the inferior vena cava.

The other options represent different vascular structures related to the gastrointestinal and circulatory systems. The superior mesenteric vein drains blood from the small intestine and part of the large intestine but does not drain the spleen directly. The portal vein, while involved in the pathway that takes blood to the liver, does not directly drain into the inferior vena cava. Lastly, the inferior mesenteric vein drains blood