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The pharynx is a passageway connected to esophagus and trachea. Its only function is to move food mechanically along its length.
The esophagus is a muscular tube (about 25 cm long or 10 inches) that delivers food from the pharynx to the stomach. At the junction of the esophogus and stomach is a circular smooth muscle called the lower esophageal sphincter or cardiac sphincter, which relaxes to allow food into the stomach, but then contracts to prevent the food from backing up into the esophagus.
