Though only a little bigger than a man's fist, and weighing 1/2 to 3/4 of a pound, I do a lot of work!  I beat over 100,000 times a day, pumping about 2,000 gallons of blood to the lungs and through the body.  In a 70-year lifetime, I will beat more that 2.5 billion times.

You've heard there are two sides to everything–that's true of me, too.  Each side has two chambers, upper and lower.  The right side gets used blood back from the body, carried by your veins.  The blood comes in the upper, or right atrium, chamber, then is pumped by the lower, or right ventricle, chamber to the lungs.  In the top, out the bottom.

The lungs restore oxygen and nutrients to the blood.  From the lungs, the blood returns to the left side of the heart, to the left atrium chamber.  It is then pumped down to the left ventricle and out to all parts of the body through your arteries.  Since the heart is a very important muscle, I have my own arteries to feed me and keep me healthy–the coronary arteries.

To keep all this blood pumping through the right way, I use a couple of valves as traffic cops.  Four valves open and close to let blood flow in only one direction when the heart contracts (beats).

For the heart to work properly, the four chambers must beat in an organized manner.  This is governed by an electrical impulse.  A chamber of the heart contracts when an electrical impulse moves across it.  Such a signal starts in a small bundle of highly specialized cells located in the right atrium ö the sinus node.  A discharge from this natural "pacemaker" causes the heart to beat.

There are lots of things you can do to help me keep doing the great job I was created to do.  And when I get in trouble, there are lots of things your doctor can do, too.  Working together, you guys can make my job a lot easier.

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