Acid Reflux (GERD) and the Esophagus

  • Introduction

    Gastroesophageal reflux disease (GERD) is a condition in which acids from the stomach flow back up into the esophagus (an action called reflux). Reflux occurs if the muscular actions of the lower esophagus or other protective mechanisms fail.

    Click the icon to see an animation about heartburn.

    The hallmark symptoms of GERD are:

    • Heartburn: a burning sensation in the chest and throat.
    • Regurgitation: a sensation of acid backed up in the esophagus.

    Although acid is a primary factor in damage caused by GERD, other products of the digestive tract, including pepsin and bile, can also be harmful.

    Heartburn is a condition in which the acidic stomach contents back up into the esophagus, causing pain in the chest area. This reflux usually occurs because the sphincter muscle between the esophagus and stomach is weakened. Remaining upright by standing or sitting up after eating a meal can help reduce the reflux that causes heartburn. Continuous irritation of the esophagus lining, as in severe gastroesophageal reflux disease, is a risk factor for developing esophageal cancer.

    The Esophagus

    The esophagus, commonly called the food pipe, is a narrow muscular tube about nine-and-a-half inches long. It begins below the tongue and ends at the stomach. The esophagus is narrowest at the top and bottom; it also narrows slightly in the middle.

    The esophagus consists of three basic layers:

    • An outer layer of fibrous tissue.
    • A middle layer containing smoother muscle.
    • An inner membrane, which contains many tiny glands.
    Click the icon to see an image of the esophagus.

    When a person swallows food, the esophagus moves it into the stomach through the action of wave-like muscle contractions, called peristalsis. In the stomach, acid and various enzymes break down the starch, fat, and protein in food. The lining of the stomach has a thin layer of mucus that protects it from these fluids.

    If acid and enzymes back up into the esophagus, however, its lining offers only a weak defense against these substances. Instead, several other factors protect the esophagus. The most important structure protecting the esophagus may be the lower esophageal sphincter (LES). The LES is a band of muscle around the bottom of the esophagus, where it meets the stomach.

    • After a person swallows, the LES opens to let food enter the stomach. It then closes immediately to prevent regurgitation of the stomach contents, including gastric acid.
    • The LES maintains this pressure barrier until food is swallowed again.
    Click the icon to see an image of the stomach.

    If the pressure barrier is not enough to prevent regurgitation and acid backs up (reflux), peristaltic action of the esophagus serves as an additional defense mechanism, pushing the backed-up contents back down into the stomach.