A new theory of micturition and urinary continence based on histomorphological studies. 2. The musculus sphincter...

Results of a histomorphological study of serial sections carried out in frontal, transversal and sagittal directions in 65 bladder necks are presented. It is shown that the trigonal system of the urinary bladder consists of two anatomical structures: first, of a muscle originating from the muscle system of both ureters and converging to form within the bladder the interureteric ridge, the musculus interuretericus and of a second structure forming the actual trigonum vesicae. It is the musculus sphincter trigonalis or musculus sphincter vesicae. This muscle elliptically embraces the internal urethral orifice and is only formed by one muscle lamella. It does not as has often been described extend in any form to the urethra or to the surroundings. The so-called Bell muscle does not exist. During the reproductive years the lower part of the sphincter trigonalis is strongly pervaded with prostate tissue. This could enable the muscle to have a double function: a continence function in accordance with a consequent distinction between the urinary bladder and the urethra as urinary and sexual tract, and during ejaculation the muscle could prevent the retrograde ejaculation and on the other hand the contraction of the muscle could lead to the release of the prostate secretion.