Journeys: Blood vessels. Stop 4

Doors in the veins

Blood from the leg has to go up to the heart. How does it not run back down? Hold your finger on the calf so the muscle squeezes the vein!

The muscle squeezed the vein, the upper door opened and the blood went up. Let go!

The lower door shut and the blood did not run back. Squeeze again!

Doors in the veins only open upwards. So when you walk, your leg muscles help the blood get back to the heart.