The urethral sphincter is a muscular structure that regulates the outflow of urine from the bladder into the urethra. There are 2 urethral sphincters, the external and internal urethral sphincters. When these muscles contract, the urethra narrows, and urination stops or slows. The urethral sphincter is critical for the maintenance of urinary continence. Urinary incontinence is usually associated with the pathology of the urethral sphincter and is a very common problem worldwide. Also, normal urethral sphincter function is necessary for ejaculation of semen in males. The urethral sphincter muscles are located within the deep perineal pouch.