Correlation 8: Gastroesophageal reflux disease

In this biopsy of the lower esophagus, the normal non-keratinizing squamous epithelium at the right has been replaced by columnar epithelium lining glands, similar to what would be seen in the stomach, though it is not normal, because goblet cells are present.

When you swallow food and liquids, they ordinarily pass down the esophagus and into the stomach, staying in the stomach. When food refluxes back up into the esophagus, then there is a burning sensation known as heartburn because the acid contents of the stomach inflame the lower esophagus. When this process occurs over months to years, then the epithelium of the lower esophagus adapts by transforming itself from squamous to columnar. This type of transformation in an epithelium is known as metaplasia.