The Urethral Rhabdosphincter, Levator Ani Muscle, and Perineal Membrane: A Review
Figure 2
Frontal sections in an 84-year-old man. Panels (a) and (c) (nerve mapping), including a longitudinal section of the urethra (UR), display nerve distributions according to immunohistochemistry using sections adjacent to panels (a) and (c) (red color: nNOS-positive nerves; green color: the other nerves). Panel (c) is located 8 mm anterior to panel (a). Abundant nerves pass through the urogenital hiatus between the rhabdosphincter area (RS) and levator ani (LA). Stars in panel (c) indicate a solid, perineal membrane along the inferior margin of the rhabdosphincter area. Insert in panel (c) emphasizes the perineal membrane. Panel (b) (immunohistochemistry for smooth muscle actin) exhibits smooth muscles in and along the inferomedial edge of the levator ani (LA) in a section near that shown in panel (a). A nerve indicated by a circle in panel (a) is shown in panel (d) (nNOS immunohistochemistry), panel (e) (VIP), and panel (f) (tyrosine hydroxylase or TH). The nNOS-positive nerve, a candidate for the cavernous nerve, usually contains TH-positive fibers. Scale bars: 10 mm in panels (a), (b), and (c); 0.1 mm in panels (d), (e), and (f). BP: bulbus penis; BS: bulbospongiosus muscle; PR: prostate.
