The swallowing system is comprised of a single tube which widens in the upper region to form cavities. Each system contains a series of valves which change the shape or configuration of the system or protect it.
Valves created by the lips and tongue keep food in the mouth and in place prior to swallowing.
The valve created by the cricopharyngeous muscle at the top of the esophagus keeps air out of the digestive system during breathing. The valve created by the soft palate keeps food out of the nasal airway during swallowing. The valves created by the false and true vocal folds and the epiglottis prevent food from entering the airway during swallowing. 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.