A functional and clinical reinterpretation of human perineal neuromuscular anatomy: Application to sexual function and continence

• Published in: Clinical anatomy (New York, N.Y.) Vol. 29; no. 8; pp. 1053 - 1058
• Main Authors: PLOCHOCKI, JEFFREY H., RODRIGUEZ-SOSA, JOSE R., ADRIAN, BRENT, RUIZ, SAUL A., HALL, MARGARET I.
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01-11-2016; Wiley Subscription Services, Inc
• Subjects: Aged; Aged, 80 and over; bulbospongiosus; external anal sphincter; Female; Humans; innervation; Male; Middle Aged; Pelvic Floor - anatomy & histology; perineal body; perineum; Perineum - innervation; Sexual Behavior - physiology; perineal body; external anal sphincter; bulbospongiosus; innervation; perineum
• ISSN: 0897-3806; 1098-2353
• DOI: 10.1002/ca.22774

Modern anatomical and surgical references illustrate perineal muscles all innervated by branches of the pudendal nerve but still organized into anatomically distinct urogenital and anal triangles with muscles inserting onto a central perineal body. However, these conflict with the anatomy commonly encountered during dissection. We used dissections of 43 human cadavers to characterize the anatomical organization of the human perineum and compare our findings to standard references. We found bulbospongiosus and the superficial portion of the external anal sphincter (EAS) were continuous anatomically with a common innervation in 92.3% of specimens. The superficial transverse perineal muscle inserted anterior and lateral to the midline, interdigitating with bulbospongiosus. The three EAS subdivisions were anatomically discontinuous. Additionally, in 89.2% of our sample the inferior rectal nerve emerged as a branch of S3 and S4 distinct from the pudendal nerve and innervated only the subcutaneous EAS. Branches of the perineal nerve innervated bulbospongiosus and the superficial EAS and nerve to levator ani innervated the deep EAS. In conclusion, we empirically demonstrate important and clinically relevant differences with perineal anatomy commonly described in standard texts. First, independent innervation to the three portions of EAS suggests the potential for functional independence. Second, neuromuscular continuity between bulbospongiosus and superficial EAS suggests the possibility of shared or overlapping function of the urogenital and anal triangles. Clin. Anat. 29:1053–1058, 2016. © 2016 Wiley Periodicals, Inc.