Digestive System A&P Practice Test

The barrier that prevents stomach contents from moving back up into the esophagus is the lower esophageal sphincter, often called the cardiac sphincter. Located at the gastroesophageal junction, this ring of smooth muscle maintains a tonic, high-pressure seal to keep gastric contents from refluxing. It relaxes briefly to allow swallowing, but otherwise stays contracted to protect the esophagus from acid. Other sphincters mentioned control different passages: the pyloric sphincter sits between the stomach and the duodenum, the anal sphincter governs bowel continence, and the Sphincter of Oddi regulates bile and pancreatic juice entering the duodenum.