The anatomy and movements of the pyloric sphincteric cylinder.

Disagreement about various aspects of the structure and function of the pylorus persists. Morbid anatomical, living anatomical, manometric and radiographic studies were done in an attempt to clarify some problems. It is shown that the pyloric ring (sphincteric ring) is not a separate anatomical structure, but that it constitutes the aboral end of the pyloric sphincteric cylinder, a muscular tube several centimeters in length. The ring does not function independently and conventional peristaltic waves do not proceed as far as the ring. Consequently the ring does not relax reciprocally with an oncoming peristaltic wave in the sense that a wave travels up to the ring, which relaxes upon its arrival. Each peristaltic wave stops on arrival at the oral end of the cylinder, simultaneously initiating a concentric or systolic contraction of the entire cylinder, including the ring. The cylinder, including the ring, is open at rest.