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About the Heart and Blood Vessels
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About the heart: |
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The heart is the hardest working muscle in the human body. Located almost in the center of the chest, the heart of a child is about the size of their fist. During an average lifetime, the human heart will beat more than three billion times - pumping an amount of blood that equals about one million barrels. The heart is always working, 24 hours a day, seven days a week - even while we are sleeping.
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A child's heart works just as hard as an adult's heart. In fact, a baby's heart may beat up to 190 times a minute, while an adult's heart usually beats between 60 and 100 times a minute. The rate at which the heart pumps gradually slows down from birth to adolescence.
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Composed of the heart and blood vessels, the cardiovascular system is responsible for circulating blood throughout the body. A healthy cardiovascular system is vital to supplying the body with oxygen and nutrients.
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How the heart works: |
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The heart is a large, hollow, muscular organ that pumps blood filled with oxygen and nutrients through the blood vessels to the body tissues. It is made up of: |
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- Four chambers (two atria and two ventricles) that receive blood from the body and pump out blood to it.
- The right and left atria receive blood coming back to the heart.
- The right and left ventricles pump the blood out of the heart.
- Four valves to prevent backward flow of blood: the aortic, pulmonary, mitral, and tricuspid valves. Each valve has flaps, called leaflets, that allow the forward flow of blood and prevent the backward flow.
- Blood vessels that bring blood to the lungs, where oxygen enters the bloodstream, and then to the body.
- The inferior and superior vena cava bring oxygen-poor (blue) blood from the body into the right atrium.
- The pulmonary artery channels oxygen-poor (blue) blood from the right ventricle into the lungs, where oxygen enters the bloodstream.
- The pulmonary veins bring oxygen-rich (red) blood to the left atrium.
- The aorta channels oxygen-rich (red) blood to the body.
- An electrical system controls how fast the heart beats.
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A network of arteries and veins also carry blood throughout the body.
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- Arteries transport blood from the heart to the body tissues.
- Veins carry blood back to the heart.
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