Anatomy Abdomen and pelvis 11b0f6d1 External anal sphincter is innervated by A L4, L5 B L5, S1 C S1, S2, S3 D S2, S3, S4 High-Yield Explanation External anal sphincter is controlled by spinal nerves from the S2, S3 and S4 levels of your spinal cord, which form the pudendal nerve. ref - BDC vol2 pg 412-416