How do minor calyxes and major calyxes collect urine?

Minor and major calyxes function as a collection system for urine within the kidney. Urine is produced in the cortex and transported through collecting tubules that converge into the ducts of Bellini within the renal pyramids.1

The apex of each renal pyramid, known as the renal papilla, projects into a minor calyx. As muscle fibers within the calyx contract, urine is discharged from the ducts of Bellini into these minor calyxes. Several minor calyxes then drain into two or three larger major calyxes.123

From the major calyxes, urine flows into the renal pelvis, which acts as a reservoir before the urine is moved into the ureter. This movement is facilitated by peristaltic waves of contraction that originate in the muscle fibers of the minor calyxes and travel through the major calyxes and ureter, effectively propelling urine toward the urinary bladder.32