But the formation of a clot is a much more complex process. Proteins secreted by the injured cells send out further signals to summon platelets to the site of injury, amplifying their activation. And clotting factors floating in the blood use yet other sensors to detect the injury. A cascade of changes is launched. Ultimately, the cascade leads to the conversion of a protein called fibrinogen into a mesh-forming protein called fibrin. Platelets, trapped in the fibrin mesh, like sardines in a net, ultimately form a mature clot.
