GLOSSARY

The pyloric sphincter is a thick ring of smooth muscle at the end of the stomach that guards the opening between the stomach and duodenum; by opening and closing in a regulated way, it controls the rate at which chyme empties into the duodenum and prevents duodenal contents (such as bile) from flowing back into the stomach.

Characteristics

• A true anatomical sphincter: unlike the lower oesophageal sphincter, it has a clear thickening of the circular muscle layer.
• Partly open: normally it is not fully closed, so liquids can pass, but it closes when a peristaltic wave arrives.

Factors Regulating Gastric Emptying