Blood Coagulation General

Blood coagulation is divided into the cellular part, which is characterized by the aggregation, cross-linking and activation of thrombocytes (blood platelets), and the plasmatic part, during which blood components form a kind of network in which circulating red blood cells (erythrocytes) become entangled and thus stabilize the clot. In a healthy person, a blood clot is formed only after injury to a vessel; fibers (consisting of collagen), which are located outside the vessel, are exposed and blood platelets attach to them, thus inducing an initial, unstable closure of the wound. This attachment (adhesion) triggers platelet activation, which leads to the release of various substances such as calcium and thrombboxane.

Thromboxane supports wound closure by mediating local vasoconstriction, while calcium is essential for the function of various factors in the plasmatic coagulation phase. In the course of their activation, platelets also change their structure so that the surface area of the platelets increases and their aggregation is somewhat more stable. The final stability of the clot is only ensured within the framework of the plasmatic portion.

As a result of the activation of the so-called coagulation cascade (consisting of various vitamin K-dependent factors) by the storage of red blood cells and the cross-linking of the blood platelets with each other, the thrombus is stabilized until the original wound is finally closed. As the wound heals, the blood clot is increasingly broken down, so that the defect is finally closed by new vascular tissue. If there is no injury, blood clotting can still be induced, which the body can effectively prevent using a contrasting system; there is a constant balance between clot formation and degradation, which is strictly controlled.

Clot formation is inhibited by various factors that reduce the effectiveness of thrombus formation, thus preventing the formation of a clot within an uninjured blood vessel. These factors include a complex consisting of Protein S and Protein C, which together have an inhibitory effect on the stabilization of the primary blood clot in the plasmatic phase of blood coagulation. It is important to note that Protein C is basically present in its active form and therefore the inhibitory activity of the two proteins depends only on their activation and combination with Protein S.If a patient now suffers from a deficiency of Protein S, the inhibitory effect of Protein S and Protein C is reduced or can theoretically be completely eliminated, so that the risk of thrombus formation without the presence of vascular injury is increased.