200077.vtt
1.41 KB
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WEBVTT
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Ouch!
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Here's how platelets form clots. This small artery has a cut.
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Blood flowing past the cut includes
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red blood cells that carry oxygen,
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platelets that come from
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white blood cell fragments,
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and clotting factors that help blood clot.
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When a blood vessel is damaged, blood cells
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and plasma ooze into surrounding tissue.
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Platelets immediately stick to the edges of the
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cut and release
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chemicals that attract more platelets.
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Eventually, a platelet plug is formed,
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and the outside bleeding stops.
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On the inside,
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clotting factors cause a cascade of activity
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that includes strands of blood-borne material
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called fibrin
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sticking together to seal the inside of the wound.
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Eventually, the blood vessel heals,
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and several days later, the blood clot dissolves.