Which two nutrient-related substances are primarily absorbed in the ileum?

Which two nutrient-related substances are primarily absorbed in the ileum?

• A. Water and sodium
• B. Glucose and amino acids
• C. Vitamin B12 and bile salts
• D. Calcium and iron

Answer: (C)

The terminal ileum specializes in reclaiming bile acids and absorbing vitamin B12. Bile acids are circulated from the liver to the intestine to help digest fats, and most are reabsorbed in the ileum to be reused. Vitamin B12, bound to intrinsic factor, is absorbed specifically in the ileum through receptors on enterocytes. This pairing is why these two substances are the primary absorbers in that segment. Water and sodium are absorbed throughout the small intestine and colon, but not predominantly in the ileum. Glucose and amino acids are mainly absorbed in the duodenum and jejunum via specific transporters. Calcium and iron absorption occur mainly in the duodenum (with some contribution from the jejunum), not primarily in the ileum.

The terminal ileum specializes in reclaiming bile acids and absorbing vitamin B12. Bile acids are circulated from the liver to the intestine to help digest fats, and most are reabsorbed in the ileum to be reused. Vitamin B12, bound to intrinsic factor, is absorbed specifically in the ileum through receptors on enterocytes. This pairing is why these two substances are the primary absorbers in that segment.

Water and sodium are absorbed throughout the small intestine and colon, but not predominantly in the ileum. Glucose and amino acids are mainly absorbed in the duodenum and jejunum via specific transporters. Calcium and iron absorption occur mainly in the duodenum (with some contribution from the jejunum), not primarily in the ileum.