A blood clot forms when blood cells and fibrin strands clump together. A clot that blocks blood flow is called a thrombus.
flow chart :
injured tissues and platelets release the clotting factor prothrombin activator and calcium ions.

prothrombin activator converts the blood protein prothrombin to thrombin.

Thrombin splits fibrinogen to form fibrin.

Fibrin fibers form a mesh over wound, trapping red blood cells and platelets.

Bleeding stop

Clot hardens and becomes smaller.

New cells grow to repair wound site.

Enzymes plasmin is released to dissolve clot.