What sphincter controls the release of chyme into the duodenum?

• A. Sphincter of Oddi
• B. Cardiac Sphincter
• C. Ileocecal Sphincter
• D. Pyloric Sphincter

Answer: (D)

The release of chyme into the duodenum is controlled by the pyloric sphincter. This ring of smooth muscle sits at the distal end of the stomach (the pylorus) and regulates gastric emptying by opening briefly to pass small, well-mixed amounts of chyme into the duodenum. It stays relatively closed to prevent too much chyme from entering at once and to coordinate digestion with the duodenum’s readiness and with hormonal and neural signals. Other sphincters have different roles—such as the Sphincter of Oddi, which governs bile and pancreatic juice entry into the duodenum; the cardiac (lower esophageal) sphincter, which prevents reflux into the esophagus; and the ileocecal sphincter, which controls flow from the ileum into the colon.