Which part of the small intestine is responsible for most nutrient absorption?

The jejunum is primarily responsible for the absorption of nutrients in the small intestine due to its structure and extensive vascularization, which increases the surface area for absorption. The inner lining of the jejunum contains numerous villi and microvilli, which are tiny finger-like projections that enhance nutrient absorption capacity. This section of the small intestine is particularly efficient at absorbing carbohydrates, proteins, and fats, making it crucial for nutrient uptake.

While the duodenum and ileum also play essential roles in the digestion and absorption process, the duodenum mainly focuses on the chemical breakdown of food with the aid of enzymes from the pancreas and bile from the liver. The ileum, on the other hand, continues absorption but is more specialized in absorbing certain nutrients, such as vitamin B12 and bile acids. The colon, which is part of the large intestine, primarily absorbs water and salts, rather than nutrients, making it less relevant to the question of major nutrient absorption. Therefore, the jejunum's specialized structure and functions make it the most significant site for nutrient absorption in the small intestine.