Assertion: esophagus's sphincter | /r/MadeOf | a bundle of muscles
Facets:
Source sentences:
text: My upper esophageal sphincter is made of a bundle of muscles (cricopharyngeal muscle) which open when food is swallowed and close the esophagus when food is not being swallowed, while my lower esophageal sphincter is made of a bundle of muscles which open to allow food to reach the stomach and close to prevent your dog’s stomach acids from making their way back up.