Gastroesophageal sphincter: a model

There is substantial experimental and anatomic evidence suggesting that the human lower esophageal sphincter is not a muscular ring but has its correlate in the arrangement of the so-called muscular clasps and oblique sling fibers at the gastroesophageal junction. We assessed the mode of action of these distinct muscle units in a mechanical model. The arrangement of the clasp and sling fibers at the gastroesophageal junction was simulated with two elastic bands placed perpendicularly around the gastroesophageal junction of four pig specimens. Rapid pullback manometry with four radially oriented pressure transducers was performed in each specimen. The opening pressure was determined, and three-dimensional pressure images were constructed based on the manometric readings. The elastic bands established a competent high-pressure zone at the level of the gastroesophageal junction. The three-dimensional pressure images matched those usually observed in vivo in normal human volunteers. The vector volume of the high-pressure zone correlated with the opening pressure while individual resting pressure values and length of the high-pressure zone were not sufficient to estimate the competence of the gastroesophageal junction in the model. This model supports the contention that the combined action of the clasp and sling fibers establishes the manometric lower esophageal sphincter in humans.