Blood clot foreign surfaces

Several investigators (9, 21, 22) have found that foreign surfaces, when exposed to blood, adsorb plasma proteins. Since platelet adhesion to the surface is the first observable event occurring in clotting on foreign surfaces, and since platelets are known to participate in hemostasis and coagulation, the indication is that platelet adhesion onto the plasma protein-coated surface plays a major role in the in vivo initiation of thrombus formation on foreign surfaces. 

Platelets adhere to each other and to foreign surfaces and this property is referred to as platelet adhesion or aggregation or similar terms. Platelet aggregation is the initial stage of formation of a blood clot and is accompanied by release of phospholipids and specific clotting factors that trigger blood coagulation. 

The adsorption of proteins is the first interaction which occurs when a foreign surface comes in contact with blood. The processes which then lead to hemostasis are attachment of cellular elements to the surface, platelet adhesion and release, and triggering of the blood coagulation cascade. Investigations of interactions of proteins at the interface, which are the primary steps in blood clotting and determine whether it will occur, are hence of fundamental importance. 

Traditionally, 2 systems of B.c. are recognized, the intrinsic and extrinsic systems. Blood plasma clots slowly (in several minutes) in the presence of a foreign surface like kaolin or glass. [For this reason, blood for clinical purposes is withdrawn into vessels... 

Blood coagulation, which takes place at the site of an injury or in response to exposure to a foreign surface, is triggered by a series of enzymatic reactions that culminate in the production of the enzyme thrombin. Thrombin is responsible for the formation of fibrin, which together with the platelets present in blood is a key ingredient of a blood clot. Most of these events take place at the contact site. 

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