Need-to-know anatomy

The esophagus transports food from the mouth to the stomach and prevents gastric or esophageal contents from moving backward into the mouth. It is a hollow tube, roughly 10 inches long; the length of the esophagus correlates with an individual's height. It is usually longer in men than in women.

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The esophagus is closed at the upper and lower ends by two rings of muscle, called "sphincters." These sphincters open to allow food through and then close to prevent the food from backing up. The upper esophageal sphincter, near the throat, prevents swallowed food from re-entering the throat. The lower esophageal sphincter, near the opening to the stomach, stops stomach acid and digested food from moving back up into the esophagus, throat, and mouth. This lower esophageal sphincter, or LES, plays a critical role in GERD.

The hollow walls of the esophagus are lined with a three-layer mucosa. The first layer is composed of soft, scalelike cells. Underneath is a supporting layer of connective tissue and then a thin layer of muscle fiber. There are two layers of muscle tissue below the mucosa that work involuntarily to move food from the mouth to the stomach.

The esophagus passes through the hiatus, an opening in the diaphragm, to join up with the stomach in the abdominal cavity at the lower esophageal sphincter. The diaphragm muscle contracts and helps to enhance the strength of the lower esophageal sphincter, which creates a barrier to the transfer of stomach contents back into the esophagus. Sometimes a weakening of the diaphragm muscle at the hiatus will cause the top part of the stomach to slip through the hiatus into the chest, and this is called a hiatal hernia.