What is the main function of the large intestine?

The primary function of the large intestine is to absorb water and electrolytes from indigestible food matter and to consolidate waste into feces. This process involves the reabsorption of water that has been used in digestion throughout the gastrointestinal tract, which is critical for maintaining hydration and electrolyte balance in the body. As the contents pass through the large intestine, they become progressively firmer and are eventually formed into stool, which is stored in the rectum until it is excreted.

In contrast, nutrient absorption occurs mainly in the small intestine before the contents reach the large intestine. Digestion of proteins also primarily happens in the stomach and small intestine, while blood filtration is a function of the kidneys rather than the digestive system. Thus, the large intestine plays a vital role specifically in water absorption and feces formation.