All of the following are components of sphincter of the lower genitourinary tract in females, EXCEPT:
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.
Bulbospongiosus
External urethral sphincter
Internal urethral sphincter
Pubovaginalis