What is the primary function of the large intestine?

• A. Absorb water and electrolytes and form feces; hosts gut microbiota
• B. Major site of bile production
• C. Secrete digestive enzymes
• D. Absorb nutrients primarily in the small intestine

Answer: (A)

The large intestine primarily absorbs water and electrolytes from indigestible material and forms solid waste (feces). This reclaiming of water helps keep you hydrated and maintains electrolyte balance, while the formation of feces concentrates waste for elimination. The gut microbiota housed there also ferments some remaining material and synthesizes vitamins such as vitamin K and certain B vitamins, which can be absorbed. The other options don’t fit because bile production happens in the liver, not the large intestine; digestive enzymes are secreted mainly by the pancreas and the small intestine to break down nutrients; and the bulk of nutrient absorption occurs in the small intestine, where there is the large surface area for uptake.