Which statement about bicarbonate concentration in ileal versus jejunal fluid is correct?

Which statement about bicarbonate concentration in ileal versus jejunal fluid is correct?

• A. Lower in ileal
• B. Varies widely and cannot be compared
• C. Higher in ileal
• D. Higher in jejunal

Answer: (C)

Bicarbonate concentration in the small-intestine lumen increases toward the distal portion because the ileal mucosa actively contributes bicarbonate to the lumen as chyme passes through. This secretion helps neutralize acidity arriving from the stomach and maintains an environment suitable for ongoing digestion and absorption (including bile acid handling and enzyme activity). As a result, luminal bicarbonate levels are higher in the ileal fluid than in the jejunal fluid. The trend is a real physiological gradient rather than a purely variable value, and it underpins why ileal contents tend to have more bicarbonate than jejunal contents.

Bicarbonate concentration in the small-intestine lumen increases toward the distal portion because the ileal mucosa actively contributes bicarbonate to the lumen as chyme passes through. This secretion helps neutralize acidity arriving from the stomach and maintains an environment suitable for ongoing digestion and absorption (including bile acid handling and enzyme activity). As a result, luminal bicarbonate levels are higher in the ileal fluid than in the jejunal fluid. The trend is a real physiological gradient rather than a purely variable value, and it underpins why ileal contents tend to have more bicarbonate than jejunal contents.