Normal physiology of the aerodigestive tract and its effect on the upper gut.

There is a close functional relation between the aerodigestive tract and the upper gastrointestinal tract. The pharynx and larynx are involved in respiration, speech, and deglutition. This article reviews the effects of reflexes emanating from the pharynx and larynx on the esophagus and its sphincters, as well as the effects of reflexes emanating from the esophagus on the larynx. Principally, reciprocal reflexes within these 2 regions result in protection of the airway against aspiration from above and below, either by swallowed or refluxed material. However, other reflexes appear to facilitate reflux of gastric content into the esophagus and inhibit esophageal motor function.