Esophageal Sphincter, Upper

**Definition:** The structure at the pharyngoesophageal junction consisting chiefly of the cricopharyngeus muscle. It normally occludes the lumen of the ESOPHAGUS, except during SWALLOWING.

**Tree numbers:** - A02.633.567.800.360 - A03.556.875.500.360 - A04.623.617.360 - A14.724.617.360

**Synonyms:** - Upper Esophageal Sphincter