We have got millions in the skin. They produce sweat, a liquid with water, waste products and mineral salts.
It filters the blood taking the waste products and harmful substances from it. Later, some organs eliminate this substances.
*Renal vein: Veins give clean blood back to the heart
*Renal artery: Arteries give blood to the kidneys
*Kidneys:They are bean-shaped organs. They filter the blood and take the waste (every day they filter about 1500 litres of blood). The kidneys mix this waste with water and produce urine.
*Ureter: Tubes to take urine from kidneys to bladder
*Bladder: Bag to store urine until you go to the toilet
*Urethra: Urine goes out through the urethra