Urethral sphincters

In mammals, the Urethal sphincters are two muscles that control the exit of urine from the bladder through the uretha. If either of them contracts, the uretha is sealed shut. In male mammals, one of the muscles is placed around the uretha. In female mammals, it is placed on the side of the vagina. In male mammals, the muscles are also used to transport the sperm, when an erection happens.