Where in the human alimentary canal is most water absorbed?

• A. Stomach
• B. Colon
• C. Small intestine
• D. Esophagus

Answer: (B)

Water absorption mainly happens in the small intestine because it has by far the largest surface area, thanks to the many villi and microvilli. As nutrients and electrolytes are absorbed through the intestinal lining, water follows them by osmosis, moving into the bloodstream along with the solutes. The colon does take up water as well, helping to form solid waste and balance electrolytes, but the total amount absorbed there is smaller compared with the small intestine. The stomach absorbs only a tiny amount of water, and the esophagus does not absorb water in any meaningful way. So, the major site where most water is reabsorbed in the digestive tract is the small intestine.