十万个为什么·科学启蒙30篇（4）

25 / 30

为什么伤口愈合会结痂

When your skin gets cut, blood flows out and begins to clot almost instantly.
Platelets in the blood stick together and form a temporary plug at the wound site.
Fibrin proteins then weave a mesh-like net to strengthen this clot further.
As the clot dries and hardens in air, it turns into a protective brownish scab.
This scab shields new skin cells growing underneath from germs and friction.
White blood cells also gather beneath it to fight off any invading bacteria.
Once healing is complete, the scab naturally loosens and falls off.
Scab formation is a vital first step in the body’s natural repair process.
Without it, wounds would stay open longer and risk serious infection.
Even small scrapes follow this same biological sequence every time.