© Oxford University Press Tubes Sudden death What could make the blood flow hard to stop? Oetzi’s death was quick. An arrow cut one of his arteries and his blood spurted out. He couldn’t stop the bleeding.

© Oxford University Press Tubes Under pressure Why so much pressure? The blood in your arteries has just left your heart. It’s under pressure …... so it can spurt into the air like water from this hose.

© Oxford University Press Tubes Off the motorway Capillaries are like streets and cells are the houses. Blood needs a hard push from the heart to get through them. Arteries are high-speed motorways for red cells… …but they run into the network of narrow capillaries that fills your muscles, bones and organs.

© Oxford University Press Tubes You have about 40 BILLION capillaries. Capillaries channel blood to cells the way roads lead cars to houses. You have about 100,000 kilometres of blood vessels and most are capillaries. Through the backstreets

© Oxford University Press Tubes A bit of a squeeze How do they find their way back to the heart? Red cells have to bend to squeeze through the smallest capillaries… …and they slow right down.

© Oxford University Press Tubes The long journey back As blood leaves each organ, capillaries join to make veins… …and these lead your blood back to your heart. One way doors called valves slam shut if it tries to slip backwards as it climbs up your legs.