The<unk>  or<unk>  bowel is an organ in the gastrointestinal tract where most of the absorption of nutrients from food takes place. It lies between the stomach and large intestine, and receives bile and pancreatic juice through the pancreatic duct to aid in digestion. The<unk>  is about 18 feet (6.5 meters) long and folds many times to fit in the abdomen. Although it is longer than the large intestine, it is called the<unk>  because it is narrower in diameter. The<unk>  has three distinct regions – the duodenum, jejunum, and<unk> . The duodenum, the shortest, is where preparation for absorption through<unk>  finger-like protrusions called villi begins. The jejunum is specialized for the absorption through its lining by enterocytes:<unk>  nutrient particles which have been previously digested by enzymes in the duodenum. The main function of the<unk>  is to absorb vitamin B12, bile salts, and whatever products of digestion that were not absorbed by the jejunum.
Small intestine
Large intestine
Stomach
Liver
Gastrointestinal tract
Gastric mucosa
Lung
Kidney