The dispute about the external sphincter and the urogenital diaphragm.

Overview

PURPOSE: Basic scientific facts, such as anatomical structures, are rarely subjected to critical reappraisal. Nevertheless, several clinical phenomena exist which are inconsistent with the description of the anatomy of the so-called external sphincter muscle and urogenital diaphragm. MATERIALS AND METHODS: We performed a global examination of the anatomy of the entire lower urinary tract in 50 male autopsy specimens. For comparison magnetic resonance imaging of the same regions was performed on 12 healthy patients. RESULTS: Direct comparison of the results of both methods revealed the exact same topography of the bladder neck. The external sphincter or musculus sphincter urethrae is an independent morphological unit separated from the surrounding pelvic floor muscles by connective tissue. CONCLUSIONS: The musculus transversus perinei profundus or deep transverse perineal muscle, which is believed to constitute the major element of the urogenital diaphragm, does not exist. There is histomorphological evidence that the external sphincter consists of a striated (musculus sphincter urethrae transversostriatus) and smooth muscle (musculus sphincter urethrae glaber) component.