Compared with jejunal fluid, which statement is true about ileal fluid bicarbonate concentration?

Compared with jejunal fluid, which statement is true about ileal fluid bicarbonate concentration?

• A. Sodium concentration is higher in ileal fluid
• B. Potassium concentration is lower in ileal fluid
• C. Bicarbonate concentration is higher in ileal fluid
• D. Chloride concentration is lower in ileal fluid

Answer: (C)

Bicarbonate secretion by the ileal mucosa makes its luminal fluid more alkaline than that of the jejunum. In the ileum, enterocytes secrete bicarbonate into the lumen via an apical chloride-bicarbonate exchanger, drawing bicarbonate from CO2 and water produced inside the cell. This process also absorbs chloride from the lumen, so ileal fluid ends up with a higher bicarbonate concentration compared with jejunal fluid. Jejunal mucosa has less bicarbonate secretion, so its luminal bicarbonate remains comparatively lower. That’s why the true statement is that bicarbonate concentration is higher in ileal fluid.

Bicarbonate secretion by the ileal mucosa makes its luminal fluid more alkaline than that of the jejunum. In the ileum, enterocytes secrete bicarbonate into the lumen via an apical chloride-bicarbonate exchanger, drawing bicarbonate from CO2 and water produced inside the cell. This process also absorbs chloride from the lumen, so ileal fluid ends up with a higher bicarbonate concentration compared with jejunal fluid. Jejunal mucosa has less bicarbonate secretion, so its luminal bicarbonate remains comparatively lower. That’s why the true statement is that bicarbonate concentration is higher in ileal fluid.