Which structure regulates gastric emptying of stomach contents into the small intestine?

• A. Cardiac sphincter
• B. Ileocecal valve
• C. Pyloric sphincter and duodenal feedback
• D. Sphincter of Oddi

Answer: (C)

Gastric emptying is controlled by a gatekeeping mechanism at the outlet of the stomach, with a feedback loop from the duodenum to fine-tune how fast chyme enters the small intestine. The pyloric sphincter acts as that gate, opening in small, regulated bursts to let chyme pass into the duodenum. The duodenum then sends feedback signals—via neural reflexes and hormones such as secretin and CCK—telling the stomach to slow down or pause emptying when the chyme is too acidic, fatty, or hypertonic, or when the duodenum is stretched. This coordination prevents overwhelming the duodenum and ensures efficient digestion. The other structures don’t regulate the passage from stomach to small intestine: the cardiac sphincter prevents reflux into the esophagus, the ileocecal valve controls movement from small to large intestine, and the Sphincter of Oddi regulates bile and pancreatic juice entry into the duodenum.