<P> Food is ingested through the mouth and when swallowed passes first into the pharynx and then into the esophagus . The esophagus is thus one of the first components of the digestive system and the gastrointestinal tract . After food passes through the esophagus , it enters the stomach . When food is being swallowed , the epiglottis moves backward to cover the larynx , preventing food from entering the trachea . At the same time , the upper esophageal sphincter relaxes , allowing a bolus of food to enter . Peristaltic contractions of the esophageal muscle push the food down the esophagus . These rhythmic contractions occur both as a reflex response to food that is in the mouth , and also as a response to the sensation of food within the esophagus itself . Along with peristalsis , the lower esophageal sphincter relaxes . </P>
what is the purpose of the muscles that line the esophagus
push the food down the esophagus .