Continence and micturition involve a balance between urethral closure and detrusor muscle activity (the muscle of the bladder). During urination, detrusor muscles in the wall of the bladder contract, forcing urine out of the bladder and into the urethra. At the same time, sphincter muscles surrounding the urethra relax, letting urine pass out of the body. The urethral sphincter is the muscular ring that closes the outlet of the urinary bladder preventing urine to pass outside the body. Urethral pressure normally exceeds bladder pressure, resulting in urine remaining in the bladder, and maintaining continence. The urethra is supported by pelvic floor muscles and tissue, allowing it to close firmly. Any damage to this balance between the detrusor muscle, urethral sphincter, supportive tissue and nerves can lead to some type of incontinence .