The Upper Esophageal Sphincter: Anatomy and Physiology
The upper esophageal sphincter (UES), also known as the pharyngoesophageal segment (PES), is a 4-cm segment of the digestive tract that separates the esophagus from the pharynx and larynx. This narrative review represents an overview of the anatomy and physiology of this critical component of the airway protective mechanism. The structure is bounded anteriorly by the larynx, posterolaterally by th