Question

Maximum water reabsorption in the gastrointestinal tract occurs in?

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

Hint:

Think of the proximal small bowel with its leaky, high-surface villous epithelium.

Answer 1

The Correct Option is B

Step 1: About 9 litres of water enters the gastrointestinal tract each day. This comes from ingested water (about 2.0 L), saliva (about 1.5 L), gastric juice (about 2.5 L), bile (about 0.5 L), pancreatic juice (about 1.5 L) and small intestinal secretions (about 1.0 L).

Step 2: Of this volume, roughly 7.7 L (about 85 percent) is reabsorbed in the small intestine and only about 1.0 to 1.5 L (5 to 10 percent) in the large intestine (colon). Around 0.2 L is finally lost in feces.

Step 3: Within the small intestine, the bulk of this water is reclaimed in the jejunum, which has a very large absorptive surface and a leaky epithelium that allows rapid water movement following solute absorption. Hence the jejunum is the single site of maximum water reabsorption.

Step 4: The colon (option d) absorbs only the residual fraction, the stomach (option a) absorbs negligible water, and the ileum (option c) absorbs less than the jejunum, so the correct answer is the jejunum.