Illustration of a section through the right kidney. The kidneys filter waste products from the blood and excrete them as urine. Each kidney consists of an outer cortex and an inner medulla. The medulla is divided into regions called the renal pyramids (darker green). Each renal pyramid drains into a renal papilla (bright green within kidney). The renal papillae merge to form the ureter (bright green tube emerging from kidney), which carries the urine to the bladder. Blood is carried to the kidneys by the renal arteries and away from them by the renal veins. From 'Traite d'Anatomie Humaine', Vol. 4 (1905) by French anatomist Leo Testut (1849-1925).