How can a hematoma help reduce bleeding from an injured blood vessel?

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Fibrin in blood clotting — bleeding and blood clotting Red blood cells (erythrocytes) trapped in a mesh of fibrin threads. Fibrin, a tough, insoluble protein formed after injury to the blood vessels, is an essential component of blood clots.

A hematoma helps reduce bleeding from an injured blood vessel by increasing external pressure on the vessel.1

When a vessel is damaged, blood escapes into the surrounding tissues, creating a pool of blood known as a hematoma. As this blood collects, it exerts pressure from the outside against the vessel wall. This increase in external pressure helps to equalize the pressure gradient between the inside and outside of the vessel, which can diminish or stop the flow of blood from the injury site.1