Small intestine

Abstract

The small intestine is a remarkably complex organ that is capable of digestion, vectorial transport (absorption and secretion), and endocrine function. In addition, the small intestine protects the internal environment against noxious ingested substances and against luminal bacteria and their toxins. It is increasingly appreciated that the mucosal immune system plays a critical role in mucosal defense, and that dysregulation of this function underlies the pathogenesis of a number of clinical disorders. The potential surface area available for digestion and absorption is amplified 600-fold by the presence of circular mucosal folds, villus mucosal architecture, and the microvillus surface of the small intestinal epithelium. Although specific properties (e.g., bile acid absorption) are confined to specific segments of the small bowel, a sizable fraction of the length of the small bowel can be removed without excessive morbidity. In fact, substantial compensatory adaptation of the remaining bowel can occur after massive resection. © 2008 Springer New York.