This corridor from the mouth to the stomach is often neglected when discussions of digestion occur. Its greatest notoriety seems to come from its involvement in GERD—or gastroesophageal reflux disease—a big name for a very painful and all-too-common problem. But more on that later.

After your mouth is done working its magic on your food, your tongue pushes the bolus (which you remember is the mass of chewed food mixed with saliva) to the back of your mouth and into your throat where it enters the pharynx—the connection between the mouth and the esophagus. When this happens, the flaps that form the opening to the pharynx actually pull together forming a slit, which prevents large chunks of food from entering and allows only the well-chewed bolus to pass through—another good reason to thoroughly chew your food.

While we don’t consciously think of it and it all happens in a split second, a complex choreography of activity occurs when you swallow. The pharynx is like an anteroom with multiple doors. Once the food enters from the mouth, the upper door shuts off the nasopharynx so food can’t go up your nose (most of the time). Another door shuts off the larynx so food doesn’t go down into your lungs. The sphincter (a contracting band of muscle) at the top of the esophagus loosens to allow the passage of food, and tightens again once food has moved into the esophagus.

This next stretch of the GI tract is a hollow, muscular tube about 10 inches long that runs alongside the trachea like a divided highway. One side directs food to the stomach and the other transports air in and out of the lungs.

Once the food bolus is in the esophagus, your autonomic nervous system takes over and swallowing is out of your control. The bolus is moved by peristalsis—wavelike movements of the muscles down the length of the esophagus—until it reaches the opening of the stomach. This peristaltic action is preceded by a wave of relaxation. This way the portion of the esophagus that the food is moving to is relaxing in anticipation of the contractions behind it. Gravity also plays a part, so if you’re upright, the food reaches the stomach more rapidly than if you’re lying down or reclining. Something you couch potatoes may want to consider.

Signals are being relayed ahead to the stomach and small intestine as well via your nervous system, and both of these areas begin to relax in anticipation of the food headed their way.  

When the food reaches the far end of the esophagus, another band of contractile muscle—the lower esophageal or gastroesophageal sphincter—relaxes to allow passage of food into the stomach. Ideally, once the food is in the stomach, this sphincter retightens just like the upper one and is controlled by both nerve impulses and hormonal secretion in the stomach.

However, many people for multiple reasons suffer from a loosening of this muscular band. The problem then lies in the ability of the food from the stomach—that is now combined with a harsh mixture of stomach acid—to slop back up into the esophagus and damage its delicate tissue. This is what countless hundreds of suffers know as GERD (gastroesophageal reflux disease) or simply reflux.