This is a cross-section of the left kidney showing the calyces pryamids and urethra; the vasculature has been omitted. The calyces are the areas in the kidney that collect urine emptying from the papilla of the renal pyramids. They converge into the renal pelvis which connects with the ureter where urine will continue to travel to the bladder and then out of the body by expulsion through the urethra.

The human kidneys process about 200 quarts of blood to sift out about 2 quarts of waste products and extra water everyday. These wastes are passed out of the body as urine. If the kidneys did not remove them these wastes would build up in the blood and damage the body. Damage to the kidneys can also occur in people who have had diabetes for many years particularly if the diabetes is not well controlled.