Each of the two |ureters| is a narrow tube which measures aproximately 14-18 inches long, and about 1/8 inch in diameter. The |ureters| pass from the |renal pelvis|, within the |kidneys|, out of the |hilus| of each |kidney|, down the back of the abdominal cavity to the |bladder|. The |ureters| allow passage of ~urine~ from the |kidneys| to the |bladder|, where it is stored awaiting discharge. Because of peristalytic waves (periodic |contractions|) starting at the |renal pelvis|, the ~urine~ is sent down the |ureters| every twenty or thirty seconds or so, rather than in a continuous flow. These peristalytic waves cause the ureteric orifice (the opening into the |bladder| from each |ureter|) to open for a few seconds as each wave sends the ~urine~ down the |ureter|, whereupon the orifice closes again to await the next wave.
