Physiology, Small Bowel

In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 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, where the majority of digestion occurs. The small intestine extends from the stomach pylorus to the ileocecal junction and is subdivided into 3 sections: the duodenum, jejunum, and ileum. Processing a single meal through the complete length of the small intestine takes up to 5 hours, coordinating 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 form stool.

The small intestine is positioned inside the inferior portion of the abdominal cavity, caudal to the stomach, and framed circumferentially 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. Comparatively, the large intestine is shorter and wider.

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