<prompt> Which muscle causes opening of the upper end of esophagus?EpiglottisThyropharungeusStylopharyngeusCricopharyngeus of inferior constrictor  <response>: Ans. is d i.e., Cricopharyngeus of inferior constrictor Upper esophageal sphinctor The upper esophageal sphincter surrounds the upper part of the esophagus. It consists of skeletal muscle, but is not under voluntary control. Opening of the upper esophageal sphincter is triggered by the swallowing reflex. The primary muscle of the upper esophageal sphincter is the cricopharyngeal part of the inferior pharyngeal constrictor. 