The small intestine is the longest part of the alimentary canal and extends from the pylorus of the stomach to the ileocecal junction. The greater part of digestion and food absorption takes place in the small intestine.
The small intestine is divided into three regions:
- The duodenum.
- The jejunum, and
- The ileum.
The duodenum is the first part of the small intestine, and most of it is deeply placed on the posterior abdominal wall. It is situated in the epigastric and umbilical regions. It is a C-shaped tube that extends from the stomach around the head of the pancreas to join the jejunum. About halfway down its length, the small intestine receives the bile and the pancreatic ducts.
The jejunum and ileum together measure about 20 ft (6 m) long; the upper two fifths of this length make up the jejunum. The jejunum begins at the duodenojejunal junction, and
The ileum ends at the ileocecal junction. The coils of jejunum occupy the upper left part of the abdominal cavity, whereas the ileum tends to occupy the lower right part of the abdominal cavity and the pelvic cavity.