Which of the following vessels receives blood from the gallbladder, pancreas, spleen, and gastrointestinal tract?

The main portal vein is the vessel that receives blood from the gallbladder, pancreas, spleen, and gastrointestinal tract. It plays a critical role in the body’s circulatory system, allowing nutrient-rich blood from these organs to flow into the liver. This is essential for several metabolic processes, including detoxification, storage of nutrients, and synthesis of various substances.

The blood that enters the main portal vein is a mixture of venous blood from the gastrointestinal tract and organs like the spleen and pancreas, which have important contributions through their venous drainage. By directing this blood into the liver, the main portal vein facilitates the liver's crucial functions of processing nutrients and filtering toxins before the blood is returned to systemic circulation.

This function distinguishes the main portal vein from other vessels listed, such as the hepatic veins, which carry blood away from the liver; the inferior vena cava, which returns deoxygenated blood from the body to the heart; and the superior mesenteric vein, which drains blood from the small intestine and parts of the colon but does not encompass the full range of organs mentioned in the question.