When urinating, urine flows from the bladder through the urethra and then leaves the body. In women, the urethra is about 4 cm long and lies against the front wall of the vagina. In men, it is about 25 cm long, is enclosed by the prostate, and then runs along the underside of the penis into the glans. During ejaculation, sperm is released into the urethra from the prostate. The sphincter muscle in the pelvic floor is located below the bladder in women and below the prostate in men.