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Right now, your heart is pumping about five quarts of blood throughout your body.
The blood travels through more than 60,000 miles of blood vessels. That includes arteries, veins, and capillaries. That’s far enough to circle the equator twice, and then some! A heart works tirelessly over a lifetime. In an average life, the heart beats 3 billion times without taking even one break. Pretty good for a muscle the size of a fist and lighter than two baseballs!
What’s the point of all this hard labor? The biggest point of all: life itself. The main purpose of your heart is to pump blood all over 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 is imbalanced—if certain chemicals are low or missing—your body systems go out of whack. If a virus invades, blood carries 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. 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.
◀ “If I only had a heart,” sings the Tin Man from The Wizard of Oz. With a heart, he says he’d be tender and gentle. “And awfully sentimental regarding love and art,” he adds. The heart doesn’t create feelings, but he knows it helps people “register emotion—jealousy, devotion.”
What’s In Your Heart of Hearts?
In a way, you have two hearts. The right heart handles only used, low-oxygen blood. The left heart deals only with oxygen-rich blood.
“Right” means the side where your right arm, 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 the heart. 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 flood of blood over and over.
Animal Hearts
▲ The hearts of reptiles and fish cannot separate oxygen-rich blood and oxygen-low blood. They don’t have enough chambers to do it.
▲ Round, thick earthworms have hearts. Thin flatworms don’t, because they’re so thin, they absorb nutrients directly through their skin. So they don’t need a pump to spread the nutrients around. Being thicker, earthworms do need a pump.
▲ A grasshopper doesn’t have any chambers at all—just one long blood vessel (a tube that carries blood) down its back!
▲ Brachiosaurus had a heart the size of a pickup truck. It pumped blood three stories high to the brain!
