Mechanisms of Acid Reflux

When we eat, food, liquids, and saliva moves down the esophagus toward the stomach. The lower esophageal sphincter (LES), located at the junction of the esophagus and stomach, opens to allow all this to pass into the stomach. The LES then constricts to restore the barrier between stomach and esophagus. In all persons, a small amount of stomach contents may be refluxed back up into the esophagus, then recede. This usually doesn't cause any side-effects in the majority of people. It's when different mechanisms of this portion of the digestive process don't work properly that acid reflux can occur. Besides causing the major symptom of gastro reflux, heartburn, these episodes may also lead to esophageal injury.

Poor Lower Esophageal Sphincter (LES) Tone
When the LES is weak, it lacks the strength needed to hold back stomach contents. These erosive contents are allowed to back up (reflux) into the esophagus.

Poor Esophageal Clearance
In a normally-functioning esophagus, when reflux occurs, the esophagus has mechanisms that will push the refluxed materials back into the stomach. If these mechanisms do not work, or work properly, the erosive stomach contents may remain in the esophagus for a prolonged period of time. This can result in irritation, and sometimes damage, to the esophageal lining.

Delayed Gastric Emptying
When the food is not emptied from the stomach quickly enough, pressure builds in the stomach. This, then, puts increased pressure on the lower esophageal sphincter. When this happens, the LES may be forced to open inappropriately. Erosive stomach contents are then allowed to back up into the esophagus.