Which circular muscle controls the movement of chyme from the stomach to the small intestine?

Which circular muscle controls the movement of chyme from the stomach to the small intestine?

• A. Pyloric sphincter
• B. Cardioesophageal sphincter
• C. External anal sphincter
• D. Sphincter of Oddi

Answer: (A)

The movement of chyme from the stomach into the small intestine is controlled by a ring of smooth muscle at the stomach’s exit, the pyloric sphincter. This circular muscle forms the pyloric canal and acts as a gatekeeper, relaxing briefly to let small amounts of chyme pass into the duodenum while also regulating the rate of emptying. This ensures mixed chyme with gastric acid and enzymes is delivered gradually for proper digestion and absorption, and it helps prevent duodenal overwhelm. Other sphincters mentioned have different roles: the cardioesophageal sphincter sits at the stomach–esophagus junction and mainly prevents reflux into the esophagus; the external anal sphincter controls defecation; the Sphincter of Oddi regulates the flow of bile and pancreatic juice into the duodenum, not the movement of chyme out of the stomach.

The movement of chyme from the stomach into the small intestine is controlled by a ring of smooth muscle at the stomach’s exit, the pyloric sphincter. This circular muscle forms the pyloric canal and acts as a gatekeeper, relaxing briefly to let small amounts of chyme pass into the duodenum while also regulating the rate of emptying. This ensures mixed chyme with gastric acid and enzymes is delivered gradually for proper digestion and absorption, and it helps prevent duodenal overwhelm.

Other sphincters mentioned have different roles: the cardioesophageal sphincter sits at the stomach–esophagus junction and mainly prevents reflux into the esophagus; the external anal sphincter controls defecation; the Sphincter of Oddi regulates the flow of bile and pancreatic juice into the duodenum, not the movement of chyme out of the stomach.