Upper esophageal sphincter

Definition

The upper esophageal sphincter (UES) is a ring of muscle at the top of the esophagus that controls the passage of food from the pharynx into the esophagus. It opens during swallowing and closes to prevent backflow of food and acid.

Related terms

Swallowing: The complex process involving voluntary and involuntary muscle movements that transport food from the mouth through the pharynx and into the esophagus.

Pharynx:

A muscular tube that connects your nasal cavities to your mouth and esophagus, playing an essential role in breathing, swallowing, and speaking.

Gastroesophageal Reflux Disease (GERD): A chronic condition where stomach acid flows back into the esophagus, often caused by a malfunction of the lower esophageal sphincter