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': 'All of the following are components of sphincter of the lower genitourinary tract in females, EXCEPT: \nSelect and explain. \nA. Bulbospongiosus, B. External urethral sphincter, C. Internal urethral sphincter, D. Pubovaginalis', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Muscles compress the vagina and act like sphincters: pubovaginalis, external urethral sphincter (especially its urethrovaginal sphincter pa), and bulbospongiosus. The internal urethral sphincter, which is formed from the detrusor muscle, is the upper and involuntary sphincter. Ref: Clinical and Surgical Anatomy, 2/e By Singh, 2006, Page 194; Clinically Oriented Anatomy by Keith L. Moore, Ahur F. Dalley, 1999, Page 372.', 'role': 'assistant'}]