wall of the gut tube has layer of smooth muscle that run both circulary and longitudinally contraction of these muscles produces

The action of smooth muscle in the intestinal wall produces tonic contractions that maintain organ dimension against an imposed load such as a bolus of food, as well as forceful contractions that produce muscle shortening to propel the bolus along the gastrointestinal tract. These functions are regulated by intrinsic electrical and mechanical properties of smooth muscle. Smooth muscle fibers are arranged in intertwined, rather indistinct bundles, aligned in most areas of the tube in circular and longitudinal layers. Individual smooth muscle fibers are connected to neighboring smooth muscle cells by gap junctions, which allow these cells to be electrically coupled. The important consequence of this electrical coupling is that when an area of smooth muscle becomes depolarized, that depolarization spreads outward through adjacent sections of smooth muscle - this results in a well-coordinated contraction of, for example, an entire ring of circular smooth muscle. Without electrical coupling through gap junctions, one would imagine that you would see contraction only of patches of circular or longitudinal muscle, which would have little effect on propulsion or

mixing of ingesta.