The Urethral Rhabdosphincter, Levator Ani Muscle, and Perineal Membrane: A Review
Figure 4
Comparative morphology of striated muscle insertions: the subscapularis muscle of the shoulder and the levator ani. Specimens obtained from a 95-year-old man. Panel (a) (immunohistochemistry for an intermediate filament, desmin) and panel (b) (silver staining) are near sections showing longitudinally sectioned subscapularis muscle fibers inserting into an intramuscular tendon (intra.m.tendon). Desmin spots along the tendon (panel (a)) correspond to anchor structures between the muscle and type I collagen fibers in skeletal muscles. In panel (b), type IV and other collagens (black) surrounding the muscle fibers are connected with type I collage (red) in the intramuscular tendon. Panel (c) (elastica-Masson staining) and panel (d) (immunohistochemistry for smooth muscle actin) are adjacent sections exhibiting the insertion of the levator ani (LA) to the lower rectum (REC). Longitudinally running striated muscle fibers insert into the conjoint longitudinal muscle coat of the rectum (stars). Panel (e) (silver staining) shows the inferomedial edge of the levator ani facing the rhabdosphincter (RS). Muscle fibers of both the levator and sphincter are cut transversely or obliquely, and thick fascia (stars) is interposed between these muscles. CM or LM, circular or longitudinal smooth muscles of the lower rectum. All scale bars: 1 mm.
