Upper Esophageal Sphincter

The upper esophageal sphincter (UES) is a muscular ring at the top of the esophagus, the tube that carries food from the throat to the stomach. It acts like a gate, opening to allow food and liquids to pass into the esophagus during swallowing and closing afterward to prevent air from entering the esophagus or stomach contents from refluxing back into the throat. The UES plays a crucial role in safe swallowing and protecting the airway, working automatically and coordinating with other muscles to ensure smooth movement of food from the mouth to the stomach.