system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
All of the following are components of sphincter of the lower genitourinary tract in females, EXCEPT:
assistant
The correct answer is  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.