The distal esophagus is the end of the esophagus by the stomach, notes Medscape. It is primarily smooth muscle, just like the gastrointestinal tract, while the proximal esophagus by the throat is striated muscle. The central section transitions from striated to smooth muscle. The muscle layers perform peristalsis, pushing food to the stomach.
At the end of the distal esophagus is the lower esophageal sphincter, or LES, according to Medscape. This is virtually all smooth muscle in composition and keeps gastric acid from flowing back up into the esophagus in a phenomenon known as acid reflux. Up at the proximal end, the upper esophageal sphincter, or UES, keeps air from making its way into the gastrointestinal tract.
The distal esophagus is the most likely section for the formation of an esophageal ring, explains Medscape. This is a structural anomaly consisting of three layers of mucosa, submucosa and muscle. Some rings, such as a Schatzki ring, form in the distal esophagus as an additional line of defense against acid reflux. However, some researchers question whether rings actually serve a protective function, as they also commonly cause meat impaction in the esophagus, including the phenomenon known as "steakhouse syndrome," when meat not thoroughly chewed lodges in place. Some rings form singly, while others are a part of formations with multiple rings.