The way home
After blood drops off its oxygen all around your body, it needs to get back to the heart. It travels home through veins, the tubes that carry blood to the heart.
Small veins join into bigger veins, like little streams flowing into a big river. In the end, they all pour into the two biggest veins of all. Together they are called the vena cava (VEE-nuh KAY-vuh).
Vena cava means hollow vein in Latin.
Top and bottom
The superior vena cava is the top one. Superior means above. It collects blood from your head, neck, arms and chest.
The inferior vena cava is the bottom one. Inferior means below. It collects blood from your belly, hips and legs. It is the biggest vein in your whole body.
Both of them empty into the right atrium, the top right room of your heart.
What happens next
The blood in the vena cava is low on oxygen. It has given most of its oxygen away and picked up carbon dioxide, a waste gas.
From the right atrium, it goes down to the right ventricle, which sends it to your lungs. There it drops off the waste and picks up fresh oxygen.
Then it comes back to the left side of the heart, ready for another trip around the body.