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Figure 9b. (a) Midanal sagittal T2-weighted fast spin-echo (2,826/120) MR image obtained with endoanal coil and (b) corresponding drawing in a 30-year-old asymptomatic female volunteer demonstrates the internal sphincter (IS), longitudinal muscle (LM), external sphincter (ES), puborectal muscle (PR), levator ani muscle (LA), perineal body (P), vagina (V), urethra (U), bladder (B), and rectum (R) (window settings optimized for demonstration of the external sphincter).