Pudendal nerve supplying motor pa to external sphincter is derived from: (A) L5 - S1 roots, (B) S1 - S2 roots, (C) L2 - L3 roots, (D) S2 - S3 roots
Answer is D. The striated sphincter is innervated by the pudendal nerve from the S2 - S3 nerve roots. The neurons that innervate the urethral sphincter originate in the cord, in an area termed Onuf&;s nucleus. The autonomic nervous system also controls the IUS muscle because it is made of smooth muscle fibers.