title: The male bulbospongiosus muscle and its relation to the external anal sphincter.
abstract: OBJECTIVE
  The bulbospongiosus muscle is part of the superficial muscular layer of the perineum and pelvic floor. Its morphology remains controversial in the literature. Therefore, we reinvestigated the fascial arrangement and fiber courses of the bulbospongiosus muscle and its topographical relation to the external anal sphincter.
  
  
  METHODS
  The perineum was dissected in 9 male cadavers (mean ± SD age 78.3 ± 10.7 years). Select samples were obtained for histology and immunohistochemistry. In 43 patients (mean age 60.7 ± 12 years) the topographical relation between the bulbospongiosus muscle and the external anal sphincter was determined by magnetic resonance imaging.
  
  
  RESULTS
  The perineum contains several fascial layers consisting of elastic and collagen fibers as well as bundles of smooth muscle cells. The bulbospongiosus muscle was subdivided into a ventral and dorsal portion, which developed in 4 variants. The ventral insertion formed a morphological unity with the ischiocavernous muscle while the dorsal origin had a variable relation to the external anal sphincter (5 variants). A muscle-like or connective tissue-like connection was frequently present between the muscles. However, in some cases the muscles were completely separated.
  
  
  CONCLUSIONS
  We suggest a concept of variations of bulbospongiosus muscle morphology that unifies the conflicting literature. Its ventral fiber group and the ischiocavernosus muscle form a functional and morphological unity. While the bulbospongiosus muscle and the external anal sphincter remain independent muscles, their frequent connection might have clinical implications for perineal surgery and anogenital disorders.
authors.affiliation: Department of Anatomy, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany.
authors.forename: Kevin
authors.initials: K
authors.lastname: Peikert
authors.affiliation: Department of Radiology, University Hospital Dresden, Dresden, Germany.
authors.forename: Ivan
authors.initials: I
authors.lastname: Platzek
authors.affiliation: Laboratory of Experimental Surgery, Faculty of Medicine, Paris-Sud 11 University and Department of Urology, Bicêtre University Hospital, Le Kremlin-Bicêtre, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Bessède
authors.affiliation: Department of Anatomy, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany. Electronic address: Albrecht.May@tu-dresden.de.
authors.forename: Christian Albrecht
authors.initials: CA
authors.lastname: May
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001003:Anal Canal / Q000033:anatomy & histology*; D002102:Cadaver; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000033:anatomy & histology*; D017773:Pelvic Floor / Q000033:anatomy & histology*; D010502:Perineum / Q000033:anatomy & histology*
keywords: anal canal; anatomy and histology; muscle; penis; perineum; smooth