Motor and Sensory Function

Motor activity of the small intestine and colon has evolved to subserve the basic physiological functions of these parts of the gastrointestinal tract. In the small intestine, motility propels food, chyme, and stool along the gut, promotes mixing of chyme with intestinal enzymes to facilitate digestion, and increases contact time between luminal contents and the mucosa, thereby promoting absorption. In the colon, in contrast, tone is an important feature, permitting changes in volume to accommodate stool; the colon is also capable of periodically generating high-amplitude phasic contractions that traverse the organ and propel stool into the rectum. Coordinated activity in the rectum, anal sphincters, pelvic floor, and abdominal musculature and diaphragm affect defecation and maintain continence.