Definition

Achalasia is a disorder of the esophagus that prevents
normal swallowing.

Description

Achalasia affects the esophagus, the tube that carries
swallowed food from the back of the throat down into the
stomach. A ring of muscle called the lower esophageal
sphincter encircles the esophagus just above the entrance to
the stomach. This sphincter muscle is normally contracted
to close the esophagus. When the sphincter is closed, the
contents of the stomach cannot flow back into the esophagus.
Backward flow of stomach contents (reflux) can irritate
and inflame the esophagus, causing symptoms such as
heartburn. The act of swallowing causes a wave of
esophageal contraction called peristalsis. Peristalsis pushes
food along the esophagus. Normally, peristalsis causes the
esophageal sphincter to relax and allow food into the stomach.

In achalasia, which means