How the Body Works : The Alimentary Canal

The alimentary canal extends from the pharynx to the rectum. When a ball of food enters the gullet, circular muscle fiber contract behind it and relax in front of it. Outer longitudinal fibers produce wavelike movements along the length of the tube. These two actions continue to push food through all the alimentary canal. The involuntary process is called peristalsis. When this action is reversed, it is called antiperistalsis and produces vomiting.