Gag Reflex - Reflexive Pharyngeal Swallow

Reflexive Pharyngeal Swallow

Closely related to the gag reflex, in which food or other foreign substances are forced back out of the pharynx, swallowing generally pushes food through the digestive system into the stomach. This reflex in particular functions as a protective system for the upper respiratory tract as it not only forces the glottis to close, thereby preventing any substances getting into the airways, but also clears the pharynx of any residual substances by a swallow.

This particular reflex is simply one of several aero digestive reflexes such as the reflexive pharyngeal swallow, the pharyngoglottal closure reflex, in which no swallowing occurs yet the glottis still closes, and the pharyngo-upper esophageal sphincter contractile reflex, occurring mainly during gastroesophageal reflux episodes. All either forcibly close the glottis or allow the pharynx to remove particles into the digestive tract that may have been forced back up by both this tract and the upper respiratory tract. These reflexes can also protect the airways from any food or liquids that may spill over from the hypopharynx. The hypopharynx is the bottom part of pharynx, and can be considered the first area where the digestive tract splits from the airways. However, if the maximum capacity of fluids that the hypopharynx can safely hold is exceeded, then this excess fluid spills into the larynx and from there into the lungs. Therefore these reflexes prevent levels reaching this maximum volume.

Since both the digestive system and the respiratory system are connected by the pharynx, there are many problems and diseases that occur when the body is unable to regulate passage of food and air into the appropriate tracts. Perhaps the most preventable cause of damage to these reflexes originates from smoking. One study has shown that, when compared to non-smokers, the threshold volumes (in other words the lowest volume at which one of these reflexes is triggered) for both the pharyngo-upper esophageal sphincter contractile reflex and reflexive pharyngeal swallowing is increased.