Mechanisms of reflux-induced epithelial injuries in the esophagus.

The esophagus is lined by a moist stratified squamous epithelium. In humans, this epithelium, as evidenced by the Bernstein test, has considerable capacity to resist damage even upon direct contact of high concentrations of luminal acid. This intrinsic property of the epithelium to defend itself against luminal acid is called "tissue resistance." Tissue resistance is comprised of a number of important structures and functions, the individual functions of which are described in this review. Moreover, when luminal acidity is sufficiently noxious, tissue resistance can be overcome, leading to heartburn and ultimately cell necrosis. Herein are described the mechanisms by which acid overcomes the epithelial defense to produce these typical signs and symptoms of gastroesophageal reflux disease.