A thrombus, or blood clot, is the final product of the blood coagulation step in hemostasis. It is achieved via the aggregation of platelets that form a platelet plug, and the activation of the humoral coagulation system (i.e. clotting factors). A thrombus is normal in cases of injury, but pathologic in instances of thrombosis. Mural thrombi are thrombi adherent to the vessel wall. They are not occlusive and affect large vessels, such as heart and aorta.