title: On the anatomy and histology of the pubovisceral muscle enthesis in women.
abstract: OBJECTIVE
  The origin of the pubovisceral muscle (PVM) from the pubic bone is known to be at elevated risk for injury during difficult vaginal births. We examined the anatomy and histology of its enthesial origin to classify its type and see if it differs from appendicular entheses.
  
  
  METHODS
  Parasagittal sections of the pubic bone, PVM enthesis, myotendinous junction, and muscle proper were harvested from five female cadavers (51-98 years). Histological sections were prepared with hematoxylin and eosin, Masson's trichrome, and Verhoeff-Van Gieson stains. The type of enthesis was identified according to a published enthesial classification scheme. Quantitative imaging analysis was performed in sampling bands 2 mm apart along the enthesis to determine its cross-sectional area and composition.
  
  
  RESULTS
  The PVM enthesis can be classified as a fibrous enthesis. The PVM muscle fibers terminated in collagenous fibers that insert tangentially onto the periosteum of the pubic bone for the most part. Sharpey's fibers were not observed. In a longitudinal cross-section, the area of the connective tissue and muscle becomes equal approximately 8 mm from the pubic bone.
  
  
  CONCLUSIONS
  The PVM originates bilaterally from the pubic bone via fibrous entheses whose collagen fibers arise tangentially from the periosteum of the pubic bone.
authors.affiliation: Biomechanics Research Laboratory, Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109-2125, USA. jinyongk@umich.edu
authors.forename: Jinyong
authors.initials: J
authors.lastname: Kim
authors.forename: Rajeev
authors.initials: R
authors.lastname: Ramanah
authors.forename: John O L
authors.initials: JO
authors.lastname: DeLancey
authors.forename: James A
authors.initials: JA
authors.lastname: Ashton-Miller
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002102:Cadaver; D003238:Connective Tissue / Q000033:anatomy & histology* / Q000737:chemistry; D005260:Female; D024022:Fibrillar Collagens / Q000032:analysis; D006801:Humans; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000737:chemistry; D011630:Pubic Bone / Q000033:anatomy & histology*; D013194:Staining and Labeling
chemical_list: D024022:Fibrillar Collagens