Peristalsis

Peristalsis is a radially symmetrical contraction and relaxation of muscles which propagates in a wave down the muscular tube, in an anterograde fashion. In humans, peristalsis is found in the contraction of smooth muscles to propel contents through the digestive tract. It is wave contraction of longitudinal and circular muscles preceded by wave relaxation of these muscles. Earthworms use a similar mechanism to drive their locomotion.