Duodenum:The first part of the small intestine immediately beyond the stomach, which receives partially digested food from the stomach and begins absorption of nutrients.
Ileum:The final and longest segment of the small intestine, it follows the jejunum and absorbs vitamin B12, bile salts, and whatever products of digestion were not absorbed by the jejunum.
Nutrient absorption: The process by which digested food substances are taken up from the gastrointestinal tract into the blood or lymph, primarily occurring in the small intestine