How is physiology of esophagus UES?

• I. Upper esophageal sphincter (UES): This 3–5 cm high-pressure zone at the esophageal upper border is composed primarily of the cricopharyngeus muscle and relaxes during swallowing to allow food bolus passage. • II. Peristalsis : These wavelike movements in the central portion of the esophagus pass down the body of the esophagus and become stronger toward the lower portion. ➢Primary peristalsis: propels food down the esophagus ➢Secondary peristalsis: If a food bolus fails to progress, local stretch receptors trigger secondary peristalsis to move it.