Why does Blood Clot?

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Bleeding occurs when our skin gets damaged and the blood vessels near the surface are broken. This bleeding does not continue for long because our blood contains special substances which form a clot that dries and checks the flow of blood. An enzyme called thrombin present in the blood, initiates the process of clotting. This acts upon a protein called fibrinogen and changes it to fibrin. Fibrin consists of many long fibres that become entangled into each other, trapping blood cells as they form. A clot is consequently formed of fibrin and blood cells and only the colourless blood serum passes through it. The clot forms a protective covering over the wound.

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