Constipation may result from reabsorbing too much of which liquid into the bloodstream?

• A. Water
• B. Blood
• C. Saliva
• D. Plasma

Answer: (A)

The key idea is how water balance in the digestive tract affects stool consistency. In the large intestine, water is reabsorbed from the digested material back into the bloodstream. If too much water is reabsorbed, the stool becomes dry and hard, making it difficult to pass and leading to constipation. Water is the liquid involved in this process of stool hydration, whereas saliva is produced in the mouth, and blood and plasma are parts of the circulatory system, not the material being formed into stool. So reabsorbing excess water into the bloodstream is what tends to cause constipation.