Renal calyx

The renal calyces are conduits in the kidney through which urine passes. The minor calyces form a cup-shaped drain around the apex of the renal pyramids. Urine formed in the kidney passes through a renal papilla at the apex into the minor calyx; 4-5 minor calyces converge to form a major calyx through which urine passes into the renal pelvis (which in turn drains urine out of the kidney through the ureter).

Function
Peristalsis of the smooth muscle originating in pace-maker cells originating in the walls of the calyces propels urine through the renal pelvis and ureters to the bladder. The initiation is caused by the increase in volume that stretches the walls of the calyces. This causes them to fire impulses which stimulate rhythmical contraction and relaxation, called peristalsis. Parasympathetic innervation enhances the peristalsis while sympathetic innervation inhibits it.

Clinical significance


A "staghorn calculus" is a kidney stone that may extend into the renal calyces.

A renal diverticulum is diverticulum of renal calyces.