Morphology of the region anterior to the anal canal in males: visualization of the anterior bundle of the longitudinal muscle by transanal ultrasonography

Nakajima, Yasuo; Muro, Satoru; Nasu, Hisayo; Harada, Mikio; Yamaguchi, Kumiko; Akita, Keiichi

doi:10.1007/s00276-017-1832-0

Cited by 22 publications

(51 citation statements)

References 18 publications

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“…The perineal body has been described as a fibromuscular tissue and as the central point of attachment for several structures, including the perineal muscles, the levator ani muscle, longitudinal muscle of the rectum, and the rectourethralis (Oh and Kark 1973;Zhai et al 2011;Wu et al 2015). Using magnetic resonance imaging, Larson et al (2010) confirmed the presence of the perineal body and demonstrated that it has three regions, which was supported by the studies by Nakajima et al (2017) and Muro et al (2018Muro et al ( , 2019. They reported that the perineal body in both males and females is found in the area between the rectum and urogenital structures and contains both smooth and skeletal muscles.…”

Section: Perineal Bodymentioning

confidence: 62%

“…The perineum is the caudal layer of the pelvic floor, which is involved in various types of perineal surgeries, such as a perineal prostatectomy. This region is recognized as a particularly complex region in males compared to females (Muro et al 2018;Nakajima et al 2017;Oh and Kark 1973). The morphology of the male perineum has been described in general anatomy textbooks (e.g., Standring 2016).…”

Section: Introductionmentioning

confidence: 99%

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Various significant connections of the male pelvic floor muscles with special reference to the anal and urethral sphincter muscles

et al. 2019

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The male pelvic floor is a complex structure formed by several muscles. The levator ani muscle and the perineal muscles are important components of the pelvic floor. The perineal muscles comprise the external anal sphincter, bulbospongiosus, superficial transverse perineal muscles, and ischiocavernosus. Although the connections of the muscles of the pelvic floor have been reported recently, the anatomical details of each muscle remain unclear. In this study, we examined the male pelvic floor to clarify the connection between the muscles related to function. Fifteen male pelvises were used for microscopic dissection, and three male pelvises were used for histological examination. On the lateral aspect, the perineal muscles were connected to each other. Bundles of the levator ani muscle extended to connect to the perineal muscles. In addition, the extended muscle bundle from the levator ani muscle and the perineal muscles surround the external urethral sphincter. On the medial aspect, the levator ani muscle and the external anal sphincter form the anterior and posterior muscular slings of the anal canal. The connection between the perineal muscles and levator ani muscle indicates a possible close relationship between the functions of the urethra and anus.

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Section: Perineal Bodymentioning

confidence: 62%

Section: Introductionmentioning

confidence: 99%

Various significant connections of the male pelvic floor muscles with special reference to the anal and urethral sphincter muscles

et al. 2019

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“…The rectourethralis muscle laterally extended smooth muscle fibers both superiorly and inferiorly toward the levator ani and had a few fibers that inserted into the levator ani. Previous reports have mainly showed anteroposterior or superoinferior extent of the rectourethralis muscle (Brooks et al, ; Porzionato et al, ; Uchimoto et al, ; Zhai et al, ; Nakajima et al, ). In addition, the previous finding that the rectourethralis muscle connects posteriorly to the longitudinal muscle of the rectum and anteriorly to the membranous urethra coincides with that of our study.…”

Section: Discussionmentioning

confidence: 95%

“…Recent studies have described the smooth muscle tissue located between the external anal sphincter and the bulbospongiosus (indicated by number sign in Figs. , and ) as the anterior bundle of the longitudinal muscle, emphasizing the connection with the longitudinal muscle (Zhai et al, ; Nakajima et al, ). As previously mentioned, the part laterally extending inferiorly toward the levator ani (indicated by the triangle in Figs.…”

Section: Discussionmentioning

confidence: 99%

Spatial distribution of smooth muscle tissue in the male pelvic floor with special reference to the lateral extent of the rectourethralis muscle: Application to prostatectomy and proctectomy

et al. 2018

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The anatomy of the rectourethralis muscle is essential for performing radical prostatectomy and proctectomy. The rectourethralis muscle is known to continue to the rectal wall posteriorly and to the membranous urethra anteriorly. However, the lateral extent of the rectourethralis muscle remains unclear. This study aimed to verify the hypothesis that the rectourethralis muscle laterally extends and directly adheres to the levator ani. Eight male cadavers were used for macroscopic dissection, and three male cadavers were used for immunohistological analysis using anti-smooth muscle and anti-skeletal muscle antibodies. The rectourethralis muscle laterally extended smooth muscle fibers both superoposteriorly and inferoanteriorly toward the levator ani. The smooth muscle fibers sandwiched the levator ani superoanteriorly and inferoanteriorly. A few smooth muscle fibers of the rectourethralis muscle inserted into the levator ani. This study clarified the spatial distribution of the rectourethralis muscle and its detailed positional relationship with the levator ani. The findings are valuable especially to urologists and anorectal surgeons for dissecting an optimal layer around the urethra and the rectum, and for avoiding rectal or urethral injuries during surgery. Clin. Anat., 2018. © 2018 Wiley Periodicals, Inc.

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“…The anterior extension of the smooth muscle of the anorectal canal has been confirmed in males. The smooth muscle structure anteriorly, extending to the posterior urethra, is termed the rectourethralis muscle, whereas the smooth muscle structure extending anteroinferiorly to cover the anterior surface of the external anal sphincter was reported as the anterior bundle of the longitudinal muscle [7][8][9][10][11][12]. The anterior extension structure of the internal anal sphincter and rectal longitudinal muscle described in our study (indicated by the star in Figs 3b, c and 4d, h) is considered to be the structure homologous to the rectourethralis muscle of males, on the basis of the location, morphology and tissue composition.…”

Section: Discussionmentioning

confidence: 99%

Anatomy of the smooth muscle structure in the female anorectal anterior wall: convergence and anterior extension of the internal anal sphincter and longitudinal muscle

et al. 2019

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AimThe anatomy of the region between the vagina and anal canal plays an essential role when performing a proctectomy for low‐lying tumours. However, the anatomical characteristics of this area remain unclear. The purpose of the present study was to clarify the configuration, and both lateral and inferior extensions, of the muscle bundles in the anorectal anterior wall in females.MethodsUsing cadaveric specimens, macroscopic anatomical and histological evaluations were conducted at the anatomy department of our institute. Macroscopic anatomical specimens were obtained from six female cadavers. Histological specimens were obtained from eight female cadavers.ResultsThe smooth muscle fibres of the internal anal sphincter and longitudinal muscle extended anteriorly in the anorectal anterior wall of females and the muscle bundles showed a convergent structure. The anterior extending smooth muscle fibres merged into the vaginal smooth muscle layer, distributed subcutaneously in the vaginal vestibule and perineum and spread to cover the anterior surface of the external anal sphincter and the levator ani muscle. Relatively sparse space was observed in the region anterolateral to the rectum on histological analysis.ConclusionSmooth muscle fibres of the rectum and vagina are intermingled in the median plane, and there is relatively sparse space in the region anterolateral to the rectum. Therefore, when detaching the anorectal canal from the vagina during proctectomy, an approach from both the lateral sides should be used.

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Morphology of the region anterior to the anal canal in males: visualization of the anterior bundle of the longitudinal muscle by transanal ultrasonography

Cited by 22 publications

References 18 publications

Various significant connections of the male pelvic floor muscles with special reference to the anal and urethral sphincter muscles

Various significant connections of the male pelvic floor muscles with special reference to the anal and urethral sphincter muscles

Spatial distribution of smooth muscle tissue in the male pelvic floor with special reference to the lateral extent of the rectourethralis muscle: Application to prostatectomy and proctectomy

Anatomy of the smooth muscle structure in the female anorectal anterior wall: convergence and anterior extension of the internal anal sphincter and longitudinal muscle

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