The document summarizes how blood clots form to stop bleeding from damaged blood vessels. When tissue is damaged, platelets stick to exposed collagen fibers and release substances that allow them to clump together, forming an initial plug. Thromboplastin is released and activates prothrombin into thrombin, which converts fibrinogen into fibrin fibers that form a mesh trapping blood cells into a clot. The clot then dries to form a scab that prevents further blood loss and pathogen entry into the wound.