Urethra

About the Urethra

The urethra is the tube that carries urine from the bladder to the outside of the body. It differs considerably between the sexes. In females it is short, opening in front of the vaginal opening, and this short length is one reason urinary tract infections are much more common in women. In males it is much longer and passes through the prostate gland, the pelvic floor, and the length of the penis, and it also serves as the passage for semen during ejaculation; it is described in prostatic, membranous, and spongy parts. Flow is controlled by an internal sphincter of smooth muscle at the bladder neck and an external sphincter of skeletal muscle under voluntary control. Conditions affecting the urethra include urethritis, often caused by sexually transmitted infections, urethral strictures caused by scarring, and congenital variations such as hypospadias, in which the opening is on the underside of the penis. In older men, prostate enlargement can compress the urethra and obstruct urine flow.