This study presents a new technique to observe the structure of gastric smooth muscle layers by means of the combined use of “mucosa stripping technique” and “nitric acid treatment”. The mucosa stripping technique has been described elsewhere. After the procedure, the specimens are re-emersed into 20% nitric acid solution for 3 to 7 days. By the time, the muscle fibers contract tightly and the interstitial fibrous tissues become swollen and fragil, and they are easily removed by forceps in running water. Leaving muscle structure is solidly delineated.
By this method, the author explored the detailed structure of three layers of gastric smooth muscles and individualized the special muscle bundles; namely, “anterior medial oblique muscle bundle”, “posterior medial oblique muscle bundle” and “border circular muscle bundle”. These muscle bundles constitute, so-called, “upper strain zone” in relation to the development of peptic ulcers at about the gastric angulus where almost all uclers locate.
Special interest is emphasized on an existence of “lesser curvature longitudinal muscle bundle” which is confined to the area of upper strain zone and tapering off in gradual fusion with the circular muscle bundles. Although, the functional signfiicance of these muscle bundles remains for the future study.