Describe how peristalsis moves food through the esophagus. What must food pass through to enter the stomach from the esophagus?
The esophagus, a long tube connecting the pharynx to the stomach, pushes food along quickly via waves of muscular contraction called peristalsis. As a bolus contacts the circular muscles of the esophagus, it causes the muscles to contract, thus, pushing the bolus toward the stomach. When waves of peristaltic contraction reach the muscular ring, called the sphincter, at the junction of the esophagus and the stomach, the sphincter opens to allow food entry into the stomach. The sphincter is usually closed to prevent food from re-entering the esophagus from the stomach.
