Worm-like movements in a tubular structureconsisting of alternating and orderly contractions and relaxations oflongitudinal and circular muscles leading to propulsion of substances in its centralcavity. Evident in first in esophagusand then the stomach and intestines of the digestive system in which there is arepeated process of contraction and relaxation as ingested food is movedthrough the digestive system. Peristaltic waves aidthe removal of gas from the large intestine as well enabling control of bacterialgrowth by means of removing colonies of bacteria. Gastric peristalsis appearsfor the first time at 14 weeks gestational age and in all healthy foetuses by23 weeks.