Interior Heart Anatomy, Exterior Heart Anatomy

  

How the Heart Works

It's small, a little larger than a clenched fist. Relatively simple in function, your heart's primary purpose is to pump...24 hours a day, 70 to 80 times a minute. With each beat, the heart pumps blood that delivers life-sustaining oxygen and nutrients to 300 trillion cells. Each day the average heart "beats" (or expands and contracts) 100,000 times and pumps about 2,000 gallons of blood. In a 70-year lifetime, an average human heart beats more than 2.5 billion times, pumping approximately 1 million barrels of blood.

The circulatory system is a network of flexible tubes through which blood flows as it carries oxygen and nutrients to all parts of the body. It includes the heart, lungs, arteries, arterioles (small arteries) and capillaries (minute blood vessels). It also includes venules (small veins) and veins, the blood vessels through which blood flows as it returns to the heart. If all these vessels were laid end-to-end, they would extend for about 60,000 miles--far enough to encircle the earth more than twice.