What is the function of the small intestine?

The small intestine plays a crucial role in the digestive system, primarily responsible for the digestion and absorption of nutrients from food. After food is broken down in the stomach, it enters the small intestine, where enzymes from the pancreas and bile from the liver further aid in the digestion of carbohydrates, proteins, and fats. The walls of the small intestine are lined with villi and microvilli, which significantly increase the surface area, allowing for maximum absorption of nutrients such as amino acids, fatty acids, and sugars into the bloodstream. This process is essential for providing the body with the necessary nutrients to function properly, making the small intestine a vital organ in the digestive tract.

Other options relate to functions not specific to the small intestine; for example, removing water from unwanted food pertains more to the large intestine, controlling the body is a function associated with the nervous system, and pumping blood is the job of the heart.