UNTIL recently, little was known about the mechanisms responsible for gastrointestinal motility. At the turn of the century, Bayliss and Starling1 described peristalsis as a wave of relaxation followed immediately by a wave of contraction which moved the bolus of food along the digestive tract. Although this phenomenon can be demonstrated to occur in the intestinal tract of some lower animals, present evidence suggests that comparable peristaltic waves occur only in the esophagus of man. In the small intestine of man peristalsis consists of a coordinated wave of activity in which contraction of the outer longitudinal muscle is 90° out of phase with that of the inner circular muscle. The circular muscle narrows the lumen while the longitudinal muscle opens the lumen and shortens the segment of the bowel involved.
Gastrointestinal motor activity has been characterized as either propulsive, as previously described, or pendular. Pendular movements, also known as
Schiller WR, DiDio LJA, Anderson MC. Production of Artificial Sphincters: Ablation of the Longitudinal Layer of the Intestine. Arch Surg. 1967;95(3):436–442. doi:10.1001/archsurg.1967.01330150112015
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