Affiliation:
1. Department of Clinical Anatomy Tokyo Medical and Dental University (TMDU) Bunkyo‐ku Tokyo Japan
2. Department of Urology Tokai University School of Medicine Isehara Kanagawa Japan
3. Department of Anatomy, Faculty of Medicine Srinakharinwirot University Bangkok Thailand
Abstract
ObjectivesTo elucidate the male urethral muscular structure and its relationship with the anorectal canal muscles, as establishing an anatomical foundation for urethral function will contribute to the prevention, diagnosis, and treatment of urinary incontinence.MethodsEight male cadavers were used. Using a multifaceted approach, we performed macroscopic anatomical examination, histological analysis of wide‐range serial sectioning and immunostaining, and three‐dimensional (3D) reconstruction from histological sections. In the macroscopic anatomical examination, pelvic halves were meticulously dissected in layers from the medial aspect. In the histological analysis, the tissue, including the urethra and anorectal canal, was serially sectioned in the horizontal plane. The muscular structures were reconstructed and visualised in 3D.ResultsThe membranous portion of the urethra had three muscle layers: the longitudinal and circular muscles (smooth muscle) and the external urethral sphincter (skeletal muscle). The circular muscle was connected posteriorly to the longitudinal rectal muscle. The external urethral sphincter had a horseshoe shape, with its posterior ends continuing to the external anal sphincter, forming a 3D ring‐like sphincter.ConclusionThis study revealed skeletal and smooth muscle connections between the male urethra and anorectal canal, enabling urethral compression and closure. These anatomical muscle connections suggest a functional linkage between them.
Funder
Japan Society for the Promotion of Science