One of the many complexities of the esophagus is that it encompasses the anatomical and physiological transition between two distinct regions, the oropharynx and the gut. Although there is a gradual transition between the smooth and striated muscle, motor function in the oropharynx and esophageal body are quite distinct. The ensuing discussion exemplifies this distinction, describing selected aspects of pharyngeal, gastric, and diaphragmatic functions that are inextricably entwined with esophageal functions. Similarly, swallowing is a complex, highly integrated motor response encompassing the oropharyngeal swallow, and central nervous system control mechanisms, as well as strictly esophageal components. The main function of the upper esophageal sphincter (UES) is to maintain closure of the proximal end of the esophagus unless opening is required for either swallowing or belching. Physiologically, the esophagogastric junction must perform seemingly contradictory functions. During swallowing it must facilitate the esophagogastric flow of swallowed material.