The response to vascular injury involves attachment and aggregation of platelets, coupled with initiation of the coagulation cascade. These inter-related processes ensure that the vessel injury is rapidly blocked with an aggregated clump of platelets that is then stabilized by a crosslinked fibrin matrix. Initial adherence relies on the ability of the platelet adhesion receptors to bind subendothelial matrix molecules. Platelet activation then results in the expression of high affinity integrin receptors on the cell surface that bind soluble ligands, allowing platelets to aggregate and form a haemostatic plug.