Kidney. Illustration of a section through awhole healthy human kidney. At centre left is therenal artery (red) and vein (blue) which supplyblood to, and drain blood from the kidney. Thekidney is divided into an outer cortex (brown) andpyramid- shaped units (red) of the inner medulla.Blood is passed into a network of capillaries inthe cortex ending in small tight knots calledglomeruli (not seen). Glomeruli are bloodfiltering units from which excess water andmetabolic wastes pass from the blood into tubules,where the waste turns to urine. The urine thendrains through the medullary pyramids into theureter (yellow) which passes the urine down intothe urinary bladder.
