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Figure 10b. (a) Transverse T2-weighted fast spin-echo (2,500/100) MR image obtained through the lower part of the anal sphincter with an endoanal coil and (b) corresponding drawing in a 40-year-old asymptomatic male volunteer show the internal sphincter (IS), longitudinal muscle (LM), intersphincteric space (ISS), external sphincter (ES), anococcygeal ligament (AC), and bulbocavernous muscle (BC).