The feeding and respiratory systems share a portion of the pharynx between the area behind the tongue and the area at the entrance to the larynx and the entrance to the esophagus. Since a Shared System Exists, Valves are Used to Support the Desired Activity and Protect the Alternate System During breathing the valves open to allow air to enter the nose, larynx, and trachea and close to prevent air from entering the esophagus and lower digestive tract. During swallowing the valves open to allow food to enter the digestive tract and prevent food from penetrating the nose and larynx and entering the airway. During swallowing the goal of the system is to move food into the digestive system and keep it out of the respiratory system. The following events occur rapidly and often simultaneously to support this goal.
Food is propelled from the front to the back of the mouth during the oral stage of the swallow.
The lips and sides of the tongue serve as valves to direct the food efficiently toward the pharynx. The back of the tongue elevates and moves food into the pharynx as the pharyngeal swallow is triggered. The pharyngeal constrictors contract in a peristaltic wave, moving the bolus downward. The soft palate elevates to prevent the bolus from refluxing into the nasal cavity. The hyoid and larynx elevate and the epiglottis moves downward to protect the entrance to the airway.