The heart is a big hollow muscle in the middle of your chest. Its left side pumps harder than the right, which is why you can feel the left side beating when you put your hand on your chest.
Putting the parts together
The heart has four parts called chambers. Blood comes in through the top two chambers, which are called atria (AY-tree-ah). The bottom two, called ventricles (VEHN-trih-culs), pump the blood out. In between, the blood picks up oxygen, which is necessary for our cells to work.
Working with the lungs
The right atrium takes in the "used" blood from the rest of the body. It sends it to the right ventricle, which pushes the blood out to the lungs to pick up oxygen and get rid of carbon dioxide.
The "new" blood comes back in through the left atrium and is sent out to the body through the left ventricle.
Valves, which work a little like one-way doors, makes sure that no blood backs up. All the blood flows in one direction through the heart.
Heart a-facts
- The heart is always working. It never rests. It works automatically, without the brain telling it to pump.
- Your heart is about the size of your closed fist.
- Arteries are the vessels, or tiny tubes, that carry blood from the heart to the rest of the body.
- Veins cary blood back to the heart to pick up oxygen.
- Your heart beats about 100,000 times a day! Kids' hearts beat about 70 times a minute.
- There are about 60,000 miles of blood vessels in your body.
- Your heart is protected by your ribcage.
- It only takes about 10 seconds for your blood to go from your heart to your big toe while you're active.
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