This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anatomy
[{'content': 'Pudendal nerve supplying motor pa to external sphincter is derived from? \nSelect and explain. \nA. L5-S1 roots, B. 51-S2 roots, C. L2-L3 roots, D. S2-S3 roots', 'role': 'user'}, {'content': 'Answer: D \nExplanation: S2-S3 roots. There are two sphincters of the urethra a. Internal urethral sphincter (also k/a sphincter vesicae) - it is involuntary in nature - made up of smooth muscle - supplied by sympathetic nerves, from lower thoracic & upper lumbar segments of spinal cord b. External urethral sphincter (also k/a sphincter vesicae) - it is voluntary in nature - made up of striated muscle fibres - supplied by the perineal branch of the pudendal nerve (derived from spinal nerves S2,S3 & S4) - it controls the membranous urethra and is responsible for the voluntary holding of urine.', 'role': 'assistant'}]