Question

Maximum water reabsorption in the gastrointestinal tract occurs in:

• A. Stomach
• B. Jejunum
• C. Ileum
• D. Colon

Hint:

The proximal small bowel handles the largest fluid volume, not the colon.

Answer 1

The Correct Option is B

Step 1: Each day the gut handles a huge fluid load. About 2 litres come from food and drink, and the remaining 7 litres are secretions (saliva, gastric juice, bile, pancreatic juice, intestinal juice). So roughly 9 litres of water enter the lumen daily.
Step 2: Of this, the small intestine reabsorbs the bulk, close to 8 to 8.5 litres. The colon recovers only about 0.5 to 1 litre, and barely 0.1 litre is lost in stool.
Step 3: Within the small intestine, water follows the osmotic gradient set up mainly by sodium and nutrient (glucose, amino acid) absorption. This solute uptake is most active in the proximal small intestine, so the jejunum reabsorbs the largest share of water.
Step 4: The other options absorb far less. The stomach absorbs negligible water. The ileum reabsorbs bile salts and vitamin \(B_{12}\) but less water than the jejunum. The colon concentrates stool but handles a much smaller volume.
Conclusion: Maximum water reabsorption occurs in the jejunum. Answer is option B.