<prompt> All of the following are components of sphincter of the lower genitourinary tract in females, EXCEPT:BulbospongiosusExternal urethral sphincterInternal urethral sphincterPubovaginalis  <response>: 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, 2e By Singh, 2006, Page 194; Clinically Oriented Anatomy by Keith L. Moore, Ahur F. Dalley, 1999, Page 372. 