Urethral sphincter
（重定向自Constrictor urethrae）
![Dissection of prostate showing the fibers of the external sphincter surrounding the membranous urethra and partially cradling the inferior portion of the prostate.](/Images/godic/202501/06/Prostatic_urethra.svg3507.png")
The urethral sphincter is one of two muscles used to control the exit of urine in the urinary bladder through the urethra. The two muscles are the male or female external urethral sphincter and the internal urethral sphincter. When either of these muscles contracts, the urethra is sealed shut.