What tube carries urine from the kidney to the bladder?

The tube that carries urine from a kidney to the bladder is the ureter. Humans normally have two ureters, one connected to each kidney, and each transports urine downward into the bladder.

A ureter is a narrow muscular tube lined with urothelium, a specialized stretchable lining. Waves of involuntary muscular contraction called peristalsis propel urine along it, so urine does not depend solely on gravity. The ureters enter the bladder at an angle that helps reduce backflow when the bladder contracts.

In adults, each ureter is typically about 20–30 centimeters long. Kidney stones can become lodged at natural narrowing points along the ureter, causing severe flank or groin pain, sometimes accompanied by blood in the urine. Infection, scarring, or congenital abnormalities can also interfere with urine flow.

The ureter is often confused with the urethra. The ureter runs from a kidney to the bladder; the urethra carries urine from the bladder out of the body. A fallopian tube belongs to the reproductive system, while a bronchiole is a small airway in the lungs.