日本人男子膀胱及び内尿道口筋肉について

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Muscular arrangements of the ureter, bladder, urethra and prostate obtained from 13 cadavers of the male sex were examined with a magnifying glass. On the other hand, muscular coat of the bladder neck was studied microscopically and some of these specimens were reconstructed by modelling with wax plate. Ureteral musculatures consist of three layers; namely, an external longitudinal, a middle circular and an internal longitudinal layer. The middle layer fades away when the ureter approaches the bladder, while the external and internal layer incorporate and interlace with the external, and internal longitudinal muscle layers of the bladder. Muscle layers of the bladder are separated into three layers; an external and internal longitudinal and a middle circular layer. The latter two layers are nothing else but the muscules constructed by extending and intermingling of the bundles of the former muscle. In other words, the whole muscular coat of the bladder is an entity composed of three muscle layers forming a consistent whole. Muscles of the posterior urethra are continuation of the internal and external longitudinal muscles of the bladder. At the neck of the bladder the middle circular muscle thickens itself presenting an appearance of the sphincter muscle. The part, which has been hitherto called m. trigonalis, is not the independent muscle, but composed of the internal longitudinal muscle of the bladder. Therefore we should call it as "pars trigonalis vesicae". As the internal and external longitudinal muscle of the bladder descend toward the urethra, they, intermingling their fibers, enclose half-spirally the outer wall of the urethra and the fibers branch off one after another into the parenchyma of the prostatic gland. Thus the mechanism of urination would be executed in the following order: there occurs a contraction of pars trigonalis which results in descent of the lower end of the bladder and opening of the inner urethral meatus. At the same time the detrusor muscles of the bladder are stimulated to contraction, which dispels the content of the bladder to the outside. Increasing of the intra-abdominal pressure accelerates urination.
社団法人日本泌尿器科学会の論文

日本人男子膀胱及び内尿道口筋肉について

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