A modern explanation of the gastric emptying mechanism

Abstract

Employing new investigative methods, evidence has been obtained indicating that the entire pyloric sphincter region normally executes rhythmic contractions and tends to behave as a unit, i. e., the sphincter acts in a manner similar to, not contrary to the action of the antrum and bulb. Normal gastric evacuation is dependent on a pressure gradient from the stomach to the duodenum adequate to overcome the evacuation resistance. A study of the time relations of a pyloric sphincter region cycle shows that the pyloric sphincter is open much of the time and when open it offers little resistance to gastric emptying. The resistance offered by the sphincter while contracting is usually overcome by the increased pressure developed by the pyloric antrum. Reflux of duodenal contents is prevented by contraction of the sphincter and antrum. The presence of foodstuffs or hydrochloric acid in the upper intestine retards gastric evacuation by depressing gastric motility. This retardation occurs in spite of a simultaneous depression of the sphincter and bulb. Emotional states or noxious stimuli also delay evacuation by suppressing gastric motility but not by producing pylorospasm.