The small intestine or small bowel is the part of the gastrointestinal tract between the stomach and the large intestine, The small intestine has three distinct regions - the duodenum,jejunum, and ileum
The average length of the small intestine in an adult human male is 6.9 m (22 ft 8 in), and 7.1 m (23 ft 4 in) in an adult female. The small intestine is divided into three structural parts.
The duodenum is a short structure (about 20-25 cm long) continuous with the stomach and shaped like a "C". It surrounds the head of the pancreas.
The jejunum is the midsection of the small intestine, connecting the duodenum to the ileum. It is about 2.5 m long, and contains the plicae circulares, and villi that increase its surface area. Products of digestion (sugars, amino acids, and fatty acids) are absorbed into the bloodstream here. The suspensory muscle of duodenum marks the division between the duodenum and the jejunum.
The iluem The final section of the small intestine. It is about 3 m long, and contains villi similar to the jejunum. It absorbs mainly vitamin B12andbile acids, as well as any other remaining nutrients. The ileum joins to the cecum of the arge intestine at the ileocecal junction.