200022.vtt
2.36 KB
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WEBVTT
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Air enters the body through the mouth or nose and quickly moves to the pharynx, or throat.
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From there, it passes through the larynx, or voice box, and enters the trachea.
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The trachea is a strong tube that contains rings of cartilage that prevent it from collapsing.
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Within the lungs, the trachea branches into a left and right bronchus.
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These further divide into smaller and smaller branches called bronchioles.
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The smallest bronchioles end in tiny air sacs. These are called alveoli.
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They inflate when a person inhales and deflate when a person exhales.
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During gas exchange oxygen moves
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from the lungs to the bloodstream.
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At the same time carbon dioxide
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passes from the blood to the lungs.
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This happens in the lungs between the alveoli
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and a network of tiny blood vessels
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called capillaries,
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which are located in the walls of the alveoli.
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Here you see red blood cells
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traveling through the capillaries.
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The walls of the alveoli share
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a membrane with the capillaries.
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That's how close they are.
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This lets oxygen and carbon dioxide diffuse,
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or move freely, between the respiratory
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system and the bloodstream.
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Oxygen molecules attach to red blood cells,
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which travel back to the heart.
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At the same time, the carbon dioxide molecules
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in the alveoli are blown out of the body
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the next time a person exhales.
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Gas exchange allows the body to replenish
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the oxygen and eliminate the carbon dioxide.
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Doing both is necessary for survival.