One of the 2 tubes that carry urine from the kidneys to the bladder. Each ureter is 25–30 cm long. There are 3 layers in the walls of the ureters: a fibrous outer layer; muscular middle layer; and inner watertight layer. Each ureter is supplied by blood vessels and nerves. Urine flows down the ureters partly from gravity but mainly as a result of peristalsis. Some people are born with double ureters, on 1 or both sides of the body. This sometimes causes reflux of urine, incontinence, or infection.


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