十万个为什么·科学启蒙30篇（4）
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Why Wounds Form Scabs During Healing
为什么伤口愈合会结痂
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When your skin gets cut, blood flows out and begins to clot almost instantly.
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Platelets in the blood stick together and form a temporary plug at the wound site.
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Fibrin proteins then weave a mesh-like net to strengthen this clot further.
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As the clot dries and hardens in air, it turns into a protective brownish scab.
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This scab shields new skin cells growing underneath from germs and friction.
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White blood cells also gather beneath it to fight off any invading bacteria.
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Once healing is complete, the scab naturally loosens and falls off.
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Scab formation is a vital first step in the body’s natural repair process.
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Without it, wounds would stay open longer and risk serious infection.
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Even small scrapes follow this same biological sequence every time.