Kidneys. Computer artwork of the human renal system. The kidneys (brown/red, left and right) filter waste products and water from blood that passes through the organs in the renal arteries (red) and veins (blue). The filtrate (urine) is passed down the ureters (beige) to the urinary bladder (not seen), where it is stored. On the top of each kidney is an adrenal gland (yellow). These glands produce steroid hormones, adrenaline and noradrenaline that function in controlling heart rate and blood pressure.