A tube that carries urine from the bladder out of the body, and in males also carries semen during ejaculation.
Structure
The urethra is much shorter in females, about four centimeters, than in males, where it averages about 20 centimeters and passes through the prostate, perineum, and penis.
Function
Two sphincters guard the flow: an involuntary internal sphincter at the bladder neck and a voluntary external sphincter formed by skeletal muscle in the pelvic floor.
Clinical note
Because the female urethra is short, women are more prone to ascending bladder infections. In males, an enlarged prostate often constricts the urethra and slows urination.
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