And remember, it all happens in about a minute! Listen to the Lub-Dub What's next? An inhale, of course, and a fresh breath of oxygen that can enter the blood to start the process again. In the lungs, carbon dioxide is removed from the blood and sent out of the body when we exhale. The right ventricle pumps the blood to the lungs for a little freshening up. The returning blood enters the right side of the heart. It's like the blood delivers lunch to the cells and then has to pick up the trash! When the cells use the oxygen, they make carbon dioxide and other stuff that gets carried away by the blood. The body takes the oxygen out of the blood and uses it in your body's cells. The left side of your heart sends that oxygen-rich blood out to the body. If that oxygen-rich blood doesn't circulate as it should, a person could die. To stay alive, a person needs healthy, living cells. Blood delivers oxygen to all the body's cells. Your body needs this steady supply of blood to keep it working right. The movement of the blood through the heart and around the body is called circulation (say: sur-kyoo-LAY-shun), and your heart is really good at it - it takes less than 60 seconds to pump blood to every cell in your body.
The ones that carry blood back to the heart are called veins. The blood vessels that carry blood away from the heart are called arteries. These blood vessels are attached to the heart. It moves through many tubes called arteries and veins, which together are called blood vessels. You probably guessed that the blood just doesn't slosh around your body once it leaves the heart. They open up to let the blood move ahead, then they close quickly to keep the blood from flowing backward. These valves all work to keep the blood flowing forward. The other two are called the aortic (say: ay-OR-tik) valve and pulmonary (say: PUL-muh-ner-ee) valve, and they're in charge of controlling the flow as the blood leaves the heart. They let blood flow from the atria to the ventricles. Two of the heart valves are the mitral (say: MY-trul) valve and the tricuspid (say: try-KUS-pid) valve.
The door shuts behind you and keeps you from going backward. A valve lets something in and keeps it there by closing - think of walking through a door. Well, your blood relies on four special valves inside the heart. So when the blood gets pumped, how does it know which way to go? While the ventricles are squeezing, the atria refill and get ready for the next contraction. The ventricles then squeeze, pumping blood out of the heart. The atria and ventricles work as a team - the atria fill with blood, then dump it into the ventricles. The septum's job is to separate the left side and the right side of the heart. Running down the middle of the heart is a thick wall of muscle called the septum (say: SEP-tum). Their job is to squirt out the blood to the body and lungs. The heart has a left ventricle and a right ventricle. The two chambers on the bottom are called the ventricles (say: VEN-trih-kulz). The heart has a left atrium and a right atrium. The atria are the chambers that fill with the blood returning to the heart from the body and lungs. If you're talking only about one, call it an atrium. The two chambers on top are called the atria (say: AY-tree-uh). One chamber is on the top and one chamber is on the bottom. There are two chambers on each side of the heart. The heart is made up of four different blood-filled areas, and each of these areas is called a chamber. The heart is one hard worker! Parts of the Heart Your heart does this all day and all night, all the time. That's sort of like what your heart does so it can squirt out the blood. When the heart contracts, it squeezes - try squeezing your hand into a fist. Then its muscle contracts to squirt the blood along. How does the heart beat? Before each beat, your heart fills with blood. The left side of the heart does the exact opposite: It receives blood from the lungs and pumps it out to the body. The right side of your heart receives blood from the body and pumps it to the lungs. Your heart is sort of like a pump, or two pumps in one. The blood provides your body with the oxygen and nutrients it needs. But the heart muscle is special because of what it does.