How is urine transported from the kidneys to the bladder?

Urine is transported from the kidneys to the bladder primarily through the process of peristalsis. This method involves the rhythmic contraction and relaxation of smooth muscles in the walls of the ureters, the tubes that connect the kidneys to the bladder. As urine is produced in the kidneys, it collects in the renal pelvis, and the peristaltic waves push the urine down the ureters in a controlled manner. This mechanism is essential for ensuring that urine is moved effectively and prevents backflow, maintaining a one-way flow towards the bladder.

In contrast to peristalsis, diffusion is a process involving movement from an area of higher concentration to an area of lower concentration, which does not apply to the transport of urine. Active transport refers to the movement of substances against their concentration gradient and typically involves metabolic energy, which isn't how urine travels from the kidneys to the bladder. Osmosis also involves the movement of water across a semipermeable membrane, not the transport of urine itself. Thus, the function of peristalsis is specifically suited for the coordinated movement required in this urinary transport process.