Physiology, Small Bowel

In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan.


The small intestine (small bowel) is a hollow, tubular structure with an average adult length of 22 feet (7 meters), making it the longest portion of the gastrointestinal (GI) tract and where the majority of digestion occurs. The small intestine extends from the stomach pylorus to the ileocecal junction and is subdivided into three sections: the duodenum, jejunum, and ileum. It takes up to five hours for a single meal to be processed through the entire length of the small intestine, during which time it coordinates with the stomach, gallbladder, and pancreas to cue digestive juices to break down and absorb 95% of food nutrients. The small intestine extracts excess water and sends the remaining food waste to the large intestine to be formed into a stool.

The small intestine is found coiled inside the lower portion of the abdominal cavity, sitting beneath the stomach, and framed by the large intestine. When empty and at rest, the width of the small intestine is about the width of an index finger. This small width gives it the name of the small intestine, not its length. The large intestine is shorter but wider.

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