Which region of the small intestine is the major site of nutrient absorption?

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

Answer: (B)

The main concept is how the small-intestine regions are specialized for absorption. The middle section of the small intestine, the jejunum, has the largest absorptive surface area thanks to tall villi and dense microvilli, along with abundant nutrient transporters and good blood supply. This makes it the primary site where most nutrients—carbohydrates, amino acids, and fats—are taken up after chyme mixes with bile and pancreatic juice in the duodenum. The duodenum does important digestion and some early absorption, but its surface area is smaller and its role is more about mixing enzymes and starting absorption. The ileum handles specific tasks like reabsorbing bile acids and vitamin B12, and the cecum is part of the large intestine, focusing on water and electrolyte absorption rather than nutrient uptake. So the jejunum is the region where the bulk of nutrient absorption occurs.