How does peristalsis move urine through the ureters?

Urine is transported from the kidneys to the urinary bladder primarily through peristaltic movements—rhythmic, wavelike contractions of the smooth muscle layers within the walls of the renal pelvis and ureters.123

These contractions occur every 10 to 15 seconds, beginning in the minor calyxes and traveling through the major calyxes and along the length of the ureter. This process forces urine into the bladder in discontinuous spurts. While gravity assists this downward flow—making it more efficient when standing—the powerful muscular coat of the ureter serves as the primary propelling force. The ureteric wall, which consists of longitudinal and circular muscle fibers, ensures that urine is moved effectively even against pressure. Once the urine reaches the bladder, an oblique entry through the bladder wall acts as a valve to prevent backflow.2314