What is the primary function of the liver in the human body?

The primary function of the liver is to filter blood from the digestive tract. As blood is absorbed from the intestines after a meal, it travels to the liver via the hepatic portal vein. The liver processes this blood, detoxifying substances, metabolizing nutrients, and producing vital proteins. This filtration is essential for maintaining proper levels of glucose, amino acids, and fats in the bloodstream, as well as for clearing out toxins and waste products.

While the liver is indeed one of the most metabolically active organs due to its role in a variety of biochemical processes, stating that it is "the most active" does not capture its primary function as effectively as the role of filtering blood from the digestive tract. Other organs also have critical functions and levels of activity, so this choice does not fully represent the liver's unique role in the body.