Mechanism of gastric emptying through the pyloric sphincter: a human study

The current view holds that gastric emptying is effected by the force of the antral peristaltic wave squeezing food particles through pyloric sphincter resistance. Whether this is accomplished by a reflex action was investigated.

The study comprised 12 healthy volunteers (age: 42.2+/-10.6 years). A balloon-tipped and a manometric tube were introduced into the stomach. Pressure responses in the proximal stomach, pyloric antrum, and pyloric sphincter to distension of the proximal stomach and of the antrum were recorded. Pyloric sphincter distension was induced to test its effect on antral and proximal stomach pressure. These tests were repeated in nine men after separately anesthetizing the pyloric antrum and sphincter.

Distension of the proximal stomach produced no pressure changes in the proximal stomach, pyloric antrum, or sphincter (p>0.05). Antral distension effected a significant rise in antral pressure, but not in the proximal stomach. Significant sphincter pressure decrease occurred only with antral distension volumes >50 ml. Pyloric sphincter distension produced a significant rise in antral pressure, but not in the proximal stomach. Sphincteric or antral anesthetization produced no pressure changes in the pyloric sphincter, antrum, or proximal stomach.

Pyloric sphincter relaxation upon antral distension implies a reflex relationship the authors call the "antro-sphincteric inhibitory reflex". Pyloric sphincter distension effected antral contraction, which is suggested to be a reflex in nature and which they term the "sphinctero-antral excitatory reflex". It is postulated that these two reflexes act to churn and transport gastric contents to the duodenum.