Normal kidney, gross specimen. Kidneys are part of the urinary system, filtering wastes (such as urea) from the blood and excreting them as urine. The dark areas are the renal pyramids, cone-shaped structures containing many renal tubules and ducts. The ducts empty urine into the renal pelvis, the pale region, which essentially acts as a funnel for the urine flowing to the ureter. The cortical regions on the outside, brick-red orange in colour, contain the renal corpuscles that filter the blood together with many convoluted renal tubules.