Which intestinal segment is specialized for reabsorption of bile salts and vitamin B12?

• A. Duodenum
• B. Cecum
• C. Jejunum
• D. Ileum

Answer: (D)

Reabsorption of bile salts and vitamin B12 happens mainly in the terminal portion of the small intestine. Bile acids are secreted into bile, help digest fats, and most are reabsorbed in the ileum to return to the liver in enterohepatic circulation. Vitamin B12, after binding intrinsic factor in the stomach, is also absorbed in the ileum through specialized transport mechanisms, allowing this vitamin to be reused. This region has the right transporters and receptors to handle both tasks, which is why it’s the site best suited for these processes. The other segments have different primary roles—digestion and general nutrient absorption mainly in the jejunum and duodenum, and water/electrolyte absorption with microbial interactions in the cecum—so they aren’t specialized for reabsorbing bile salts and B12.