Heart and Circulation

Did you ever send a valentine with the shape of a heart on it? Did you ever hear someone say, “That came straight from my heart?” People talk about hearts a lot. People have always known that hearts are very important.

You have a heart. Your heart does not look like a valentine heart. Your heart is a pump. When you run very fast, your heart pumps hard and fast. You can feel your heart pumping, or beating.

WHAT DOES A HEART LOOK LIKE?

Your heart looks like an upside-down pear. It is about the size of your closed fist. It is almost in the middle of your chest. It is just off to the left side.

Your heart is made of muscle. It is divided into four parts called chambers. The chambers are hollow inside. The two chambers on top are called atria. The chambers on the bottom are called ventricles. Your heart also has four valves that let blood in and out of the chambers.

Tubes called arteries come out of your heart. Tubes called veins go into your heart. Arteries and veins are also called blood vessels.

THE HEART PUMPS BLOOD

Your heart pumps blood. Blood comes into the atria or top chambers of your heart. Your ventricles, or bottom chambers, pump blood out to every part of your body.

Blood going out of your heart carries food and oxygen. Every part of your body needs food and oxygen for energy. You need energy for your body to work and for you to stay alive. Your heart pumps blood carrying food and oxygen through your arteries. Big arteries carry the blood to your legs and arms. The arteries get smaller and smaller the farther out they go. Little blood vessels called capillaries take blood to your cells. Everything in your body is made of tiny cells.

Your cells give off waste products when they make energy from food and oxygen. One of these waste products is a gas called carbon dioxide. The blood in your capillaries picks up the waste products. Capillaries connect to bigger veins. The pumping of your heart pushes the blood through your veins.

WHAT HAPPENS TO THE BLOOD IN VEINS?

Your veins carry blood back to your heart. The chambers on the right side of your heart take care of blood coming back through your veins. First, the blood comes into your right atrium, the top chamber. Your right atrium pumps the blood into your right ventricle, the bottom chamber. Your right ventricle pumps the blood through an artery into your lungs.

WHAT HAPPENS TO BLOOD IN THE LUNGS?

Your blood has to get rid of carbon dioxide. It has to get a fresh supply of oxygen. Your lungs take care of both jobs. Carbon dioxide from your blood goes into your lungs. Your lungs get rid of the carbon dioxide when you breathe out.

Then you breathe in. Your lungs get oxygen from breathing in air. Your lungs fill up with oxygen. Your blood picks up a new supply of oxygen from your lungs. Now your blood is ready to go out through your arteries to all the parts of your body.

The chambers on the left side of your heart take care of blood going out through your arteries. Special veins send blood from your lungs to your left atrium, or top chamber. The blood goes from the left atrium to the left ventricle. The left ventricle pumps the blood out through your arteries to every part of your body.

HOW DOES THE HEART PUMP?

Make a fist. Open your fist slightly, and then squeeze it closed. Open and close your fist again and again. This is sort of how your heart pumps blood. The muscles in your heart squeeze the chambers.

To open and close your fist, you have to think about doing it. You don’t have to think about squeezing your heart muscles. Your brain tells your heart to pump over and over again. Your heart pumps when you are awake. Your heart pumps when you are asleep. Your heart pumps faster when you run fast. Your body needs more oxygen when you run.

Your heart is better than any pump made. It beats over and over again, day and night. The heart of a 76-year-old person has beat nearly 2.8 billion times. It has pumped about 179 million quarts (169 million liters) of blood. No one can live if their heart stops beating for more than a few minutes.

HOW TO KEEP THE HEART HEALTHY

Hearts can get sick. The special arteries that bring blood and oxygen to the heart muscle can clog up. They can clog up with clumps of fat called plaque. Blood cannot flow through clogged arteries. Clogged arteries can cause heart attacks.

Exercise is one way to keep your heart healthy. Eating fruits, vegetables, and low-fat meats is another way to keep your heart healthy. You should have regular physical checkups. The main way to keep your heart healthy, however, is not to smoke.

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