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As you read this, your heart is pumping about five quarts of blood throughout your body.
The blood is traveling through more than 60,000 miles of blood vessels (arteries, veins, capillaries). That’s enough to circle the equator twice, and then some! A heart works tirelessly over a lifetime. During an average life, the heart beats 3 billion times without a single break. Not bad for a muscle the size of a fist and lighter than a couple of baseballs.
Your heart works so hard for one reason—to keep you alive. It pumps blood through your body all of the time. That blood contains cells and chemicals. Without blood’s precious “cargo,” your muscles and organs, your heart, and most especially you would die. If the cargo becomes imbalanced—if some chemicals are low or missing—your body systems stop working correctly. If a virus invades, the blood transports an army of disease-fighting white blood cells to the site of attack. Muscles and organs—especially the brain—need a steady supply of oxygen to live. Red blood cells carry oxygen, and without it, brain tissue begins to die off in a few minutes.
Treat your heart right, and this tireless machine will keep going and going and going.
◀ “If I only had a heart,” sings the Tin Man in The Wizard of Oz. With a heart, he says he’d be tender, gentle, “and awfully sentimental regarding love and art.” The Tin Man knows that although the heart doesn’t create feelings, it does help people “register emotion—jealousy, devotion.”
What’s In Your Heart of Hearts?
In a way, you have two hearts, because the right heart handles only used, low-oxygen blood, and the left heart only deals with oxygen-rich blood.
“Right” refers to the side of your body where your right arm, right leg, and so on are located. ▼
Pulmonic Valve
Right Atrium
Pericardium (slimy skin that keeps the heart well lubricated)
Tricuspid Valve
Right Ventricle (receives blood from the right atrium and forces blood into the pulmonary artery)
Coronary Arteries (feed oxygen-rich blood to the heart muscle)
Aorta (or main artery, carries blood from the heart’s left side to the organs of the body)
Pulmonary Artery (carries low-oxygen blood from the heart to the lungs)
Pulmonary Vein (carries oxygen-rich blood from the lungs to the heart)
Left Atrium
Mitral Valve
Left Ventricle
Check It Out!
Arteries take blood away from the heart, and veins bring blood into it, so why do arteries have to be bigger and thicker?
The powerful heart pumps blood directly into the arteries, so they have to be strong enough to handle this endless flood of blood.
Animal Hearts
▲ Reptile and fish hearts don’t have enough chambers to separate oxygen-rich blood and oxygen-low blood.
▲ Round, thick earthworms have hearts, but thin flatworms don’t. What’s the difference? Flatworms are so thin that they absorb nutrients directly through skin, so there’s no need for a pump to move nutrients through their bodies. Being thicker, earthworms do need a pump.
▲ A grasshopper has no chambers at all, just one long blood vessel (a tube for blood) that goes down its back!
▲ Brachiosaurus had a heart the size of a pickup truck; it pumped blood the equivalent of three stories up to the brain!
