All are sphincters of lower genito urinary tract of female except?

Ans is 'c' i.e. Internal urethral sphincter There is no internal urethral sphincter in females. It is present in males at the bladder neck and proximal urethral. Its function is to prevent retrograde ejaculation of semen into the bladder during the time of ejaculation.In males the detrusor muscle fibers of the bladder at the region of bladder neck and proximal urethra are organized into internal urethral sphincter which is under involuntary control.In females the musculature surrounding the internal urethral orifice of the bladder is not organized into an internal sphincter.External urethral sphincter is present in both males and females.* Vaginal sphincter is formed by the fibres of pubococcygeus known as pubovaginalis.* There are other muscles also which contribute in compressing the vaginal orifice.* The Bulbospongiosus muscle fibres run anteriorly on either side of the vagina to attach to the corpora cavernosa of the clitoris and posteriorly to perineal body. Bulbospongiosus in females acts to constrict the vaginal orifice andexpress the secretions of greater vestibular glands. * The external urethral sphincter is composed of 3 muscles - sphincter urethrae, compressor urethrae, and urethrovaginal is sphincter (or muscle); last 2 muscles found in females only.* When external urethral sphincter contracts to compress the urethra, it compresses the vaginal orifice also.Muscles of the female perineum.