Esophagus

The esophagus is a muscular tube that forms part of the digestive system. It connects the pharynx at the back of the mouth to the stomach. Its primary function is to convey food and drink to the stomach through coordinated, sequential muscular contractions.

The esophagus passes through the chest cavity, running between the trachea in front and the spine behind. It then pierces the diaphragm (the muscle separating the chest from the abdomen) and joins the stomach.

Structure

The esophageal wall consists of several layers: an inner mucosa, a submucosa, a muscular layer, and an outer covering. The inner lining of the esophagus differs from that of the stomach; it resembles a stratified surface that protects against abrasion from passing food. The muscles are arranged in both longitudinal and circular layers, enabling the tube to propel food along.

Function and peristalsis

When swallowing occurs, the esophageal muscles create waves of successive contraction called peristalsis. These waves push food downward even if the person is upside down. Both ends of the esophagus contain muscular valves (sphincters). The upper valve prevents air from being inhaled; the lower valve closes the passage to the stomach to prevent stomach contents from backing up.

Medical conditions

When the lower sphincter fails to function properly, acidic stomach contents may return upward—a condition known as reflux. Other conditions include infections of the lining, difficulty swallowing (dysphagia), and esophageal cancer. Diagnosis is typically made using an endoscope (a camera instrument passed through the mouth) or radiographic imaging.