The Heart Is a Muscle
Your heart is really a muscle. It’s located a little to the left of the middle of your chest, and it’s about the size of your fist. There are lots of muscles all over your body — in your arms, in your legs, in your back, even in your behind.
But the heart muscle is special because of what it does. The heart sends blood around your body. The blood provides your body with the oxygen and nutrients it needs. It also carries away waste.
Your heart is sort of like a pump, or two pumps in one. The right side of your heart receives blood from the body and pumps it to the lungs. The left side of the heart does the exact opposite: It receives blood from the lungs and pumps it out to the body.
How the Heart Beats
How does the heart beat? Before each beat, your heart fills with blood. Then its muscle contracts to squirt the blood along. When the heart contracts, it squeezes — try squeezing your hand into a fist. That’s sort of like what your heart does so it can squirt out the blood. Your heart does this all day and all night, all the time. The heart is one hard worker!
Parts of the Heart
The heart is made up of four different blood-filled areas, and each of these areas is called a chamber. There are two chambers on each side of the heart. One chamber is on the top and one chamber is on the bottom. The two chambers on top are called the atria (say: AY-tree-uh). If you’re talking only about one, call it an atrium. The atria are the chambers that fill with the blood returning to the heart from the body and lungs. The heart has a left atrium and a right atrium.
The two chambers on the bottom are called the ventricles (say: VEN-trih-kulz). The heart has a left ventricle and a right ventricle. Their job is to squirt out the blood to the body and lungs. Running down the middle of the heart is a thick wall of muscle called the septum (say: SEP-tum). The septum’s job is to separate the left side and the right side of the heart.
The atria and ventricles work as a team — the atria fill with blood, then dump it into the ventricles. The ventricles then squeeze, pumping blood out of the heart. While the ventricles are squeezing, the atria refill and get ready for the next contraction. So when the blood gets pumped, how does it know which way to go?
Well, your blood relies on four special valves inside the heart. A valve lets something in and keeps it there by closing — think of walking through a door. The door shuts behind you and keeps you from going backward.
The Heart Valves
Four valves regulate blood flow through your heart:
• The tricuspid valve regulates blood flow between the right atrium and right ventricle.
• The pulmonary valve controls blood flow from the right ventricle into the pulmonary arteries, which carry blood to your lungs to pick up oxygen.
• The mitral valve lets oxygen-rich blood from your lungs pass from the left atrium into the left ventricle.
• The aortic valve opens the way for oxygen-rich blood to pass from the left ventricle into the aorta, your body’s largest artery.
The Conduction System
Electrical impulses from your heart muscle (the myocardium) cause your heart to contract. This electrical signal begins in the sinoatrial (SA) node, located at the top of the right atrium. The SA node is sometimes called the heart’s “natural pacemaker.” An electrical impulse from this natural pacemaker travels through the muscle fibers of the atria and ventricles, causing them to contract. Although the SA node sends electrical impulses at a certain rate, your heart rate may still change depending on physical demands, stress, or hormonal factors.
The Circulatory System
The heart and circulatory system make up your cardiovascular system. Your heart works as a pump that pushes blood to the organs, tissues, and cells of your body. Blood delivers oxygen and nutrients to every cell and removes the carbon dioxide and waste products made by those cells. Blood is carried from your heart to the rest of your body through a complex network of arteries, arterioles, and capillaries. Blood is returned to your heart through venules and veins. If all the vessels of this network in your body were laid end-to-end, they would extend for about 60,000 miles (more than 96,500 kilometers), which is far enough to circle the earth more than twice!
Here are some things that you can do to help keep your heart happy:
Remember that your heart is a muscle. If you want it to be strong, you need to exercise it. How do you do it? By being active in a way that gets you huffing and puffing, like jumping rope, dancing, or playing basketball. Try to be active every day for at least 30 minutes! An hour would be even better for your heart!
Eat a variety of healthy foods and avoid foods high in unhealthy fats, such as saturated fats and trans fats (reading food labels can help you figure out if your favorite snacks contain these unhealthy ingredients).
• Try to eat at least five servings of fruits and vegetables each day.
• Avoid sugary soft drinks and fruit drinks.
• Don’t smoke. It can damage the heart and blood vessels.
Your heart deserves to be loved for all the work it does. It started pumping blood before you were born and will continue pumping throughout your whole life.
www.Texashartinstitute.com ( Kidshealth). Your heart&circulatory systemReviewed…(steven dowshen