Urine is transported to the outside through the urethra, which is a thin, muscular tube that extends from the urinary bladder to the exterior of the body. The length and structure of the urethra differs between males and females. In males, the urethra is about 8 inches (20 centimeters) long and extends from the urinary bladder to the exterior. It has the dual function of transporting semen as well as urine out of the body. The female urethra is only about 1.5 inches (3 to 4 centimeters) long and extends from the bladder to the exterior opening.