In Barrett's oesophagus, long-term acid reflux (leaking of acid from the stomach) causes changes in the cells lining the lower part of the pipe that goes from the mouth to the stomach (oesophagus). It is associated with symptoms like heartburn. With this condition, some of the cells lining the lower part of your oesophagus start to grow abnormally and become more like the cells that line your stomach. Usually, stomach acid is kept in the stomach by a muscular valve.
Attribution: Avallain