200083.vtt
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WEBVTT
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The heart has four chambers and four main blood vessels
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that either bring blood to the heart, or carry blood away.
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The four chambers are the right atrium and right ventricle
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and the left atrium and left ventricle.
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The blood vessels include the superior and inferior vena cava.
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These bring blood from the body to the right atrium. Next is the pulmonary artery.
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that carries blood from the right ventricle to the lungs.
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The aorta is the body's largest artery.
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It carries oxygen-rich blood from the left ventricle to the rest of the body.
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Beneath the tough fibrous coating of the heart, you can see it beating.
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Inside the chambers are a series of one-way valves.
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These keep the blood flowing in one direction.
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Dye injected into the superior vena cava, will pass through
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all the heart's chambers during one cardiac cycle.
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Blood first enters the heart's right atrium.
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A muscle contraction forces the blood through the tricuspid valve into the right ventricle.
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When the right ventricle contracts, blood is forced through the pulmonary semilunar valve
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into the pulmonary artery. Then it travels to the lungs.
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In the lungs, the blood receives oxygen then leaves through the pulmonary veins.
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It returns to the heart and enters the left atrium.
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From there, blood is forced through the mitral valve into the left ventricle.
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This is the muscular pump that sends blood out to the rest of the body.
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When the left ventricle contracts, it forces blood through the aortic semilunar valve
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and into the aorta.
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The aorta and its branches carries the blood to all the body's tissues.