In addition to gravity, muscular waves, originating in the renal pelvis, squeeze urine down the ureters and squirt it into the bladder.

In addition to gravity, muscular peristaltic waves, originating in the renal pelvis, squeeze urine down the ureters and squirt it into the bladder, the peristaltic movements consist of radially symmetrical contractions and in the relaxation of the muscles that propagate in a wave downwards in the muscular tube, in an antegrade manner, such movements are also found in the esophagus and stomach.