But it's one wild pump. It beats 100,000 times a day, pumping 2,000 gallons of blood through 100,000 miles (Miles!) of organic tubing.
We got to wondering: How does a healthy heart do it?
Essentially, the heart is a big hunk of muscles and four valves, hooked together to make a two-stage pump. Like all muscles, the heart gets its energy by oxidizing (defined) blood sugars (the oxygen also comes from the bloodstream, incidentally). This energy -- released at about 5 watts -- contracts the heart's many muscle cells, and the four chambers squeeze blood out in the proper direction. Or that's the plan, anyway.
| I'd like to direct your eyes to the non-gory diagram the American Heart Association kindly loaned us. The first thing you'll notice is that the heart has two sides. We call them "left" and "right." These sides have different jobs: The right side pumps blue (venous) blood to the lungs. The left side pumps red (arterial) blood everywhere else. Are we losing anybody? Good. Now please look at the next diagram, showing the inside of the heart. If you were a blood cell, you would enter at the upper left, through the vena cava. This big vein collects old, tired oxygen-depleted blood from all over the body and routes it to the right atrium. |
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The heart has a pair of two-stage pumps for pushing blood through the body. Courtesy of the American Heart Association.
When the right atrium squeezes, it pushes blood through the tricuspid (three-toothed) valve into the right ventricle. Like the other three heart valves, this is a one-way valve -- blood can only flow through in one direction. (Don't underestimate the importance of these valves: Valve problems hospitalized 72,000 Americans and killed 15,070 of them, according to the American Heart Association.) When the right ventricle contracts, it pushes blood through the pulmonory valve, and on into the lungs. Because it doesn't take much pressure to get blood to the lungs and back, the right side is smaller than the left.
The blood, now rich in oxygen, returns from the lungs through the pulmonory veins into the left atrium. Events on the left are essentially a high-pressure replay of what we've already seen, but of course the names have been changed to keep those red blood corpuscles from getting confused.
I've noticed you haven't mentioned coronary arteries. What's their job?
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