Investigations of the muscular architecture of the rectosigmoid junction in humans.

The rectosigmoid junction, the segment of the gut where the colon merges with the rectum, has characteristic morphologic features and specific functional significance. The purpose of this study was to investigate the precise morphology of the musculature of this junction as a preliminary step toward closer study of its function and a better understanding of intestinal motility. To this end, the topographic relations of the rectosigmoid junction were investigated in specimens from 39 human cadavers. Although these relations varied, in all cases the rectosigmoid was located intraperitoneally and was distal to the promontory of the sacrum. Examination of muscle specimens under the dissecting microscope revealed conspicuous bands of longitudinal fibers, with curved interconnections between the longitudinal and circular muscle coats. The rectosigmoid junction is not a true sphincter, although in functional terms it can be regarded as such.