Muscular architecture and manometric image of gastroesophageal barrier in the rat.

The two components of the gastroesophageal barrier, the sphincter and the crural sling, closely overlap in humans, whereas they are widely separated in the rat. This investigation correlates the anatomical components of the barrier and their manometric counterparts in this animal. Sphincteric and crural sling pressures were measured in four quadrants in 23 rats. Muscle thickness was measured at nine levels of the gastroesophageal junction in the same quadrants in 12 rats and the muscular architecture of the region was studied in 10 fresh specimens. The manometric sphincteric component is stronger on the right side where the thickest muscle fibers anchor to the anterior and posterior borders of a mucosal ridge that almost surround the cardia. Conversely, the sling pressure is highest towards the left where the muscular bundles straddle the esophagus. In conclusion, there is a close correspondence between the manometric image and the muscular architecture of the components of the gastroesophageal barrier in the rat. The anatomical arrangement of U-shaped muscular bundles oriented in opposite directions creates a particularly powerful antireflux mechanism.