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Blood

What makes the bleeding stop if you have a cut?

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December 13, 2013 4:54AM

A small cut or wound will stop bleeding due to a process called coagulation, or thrombogenesis. Coagulation is only possible due to the presence of certain enzymes in the blood. It is a complicated process, but this answer will try to make it seem simple.

Blood contains an enzyme called thrombin, which is produced in the liver. When a cut occurs, the brain sends a signal to the liver to activate the thrombin, which only becomes active when there is an open wound. Thrombin joins with a specific protein in blood plasma called fibrinogen to form incredibly tiny needlelike crystals called fibrin. The joining of these two substances creates a biochemical alliance that catches blood cells called corpuscles as they try to exit the body through the wound. This, in turn, causes the formation of a plug, or blood clot, which stops the bleeding.