koagulacj

Koagulacja, Polish for coagulation, is the biological process by which blood forms a clot to stop bleeding. It is a central component of hemostasis, working with vascular constriction and platelet function to seal injured vessels while preserving overall blood flow.

It involves platelets and a complex cascade of plasma proteins called coagulation factors. The process is traditionally divided into primary hemostasis, where a platelet plug forms, and secondary hemostasis, where a coagulation cascade generates thrombin and a fibrin mesh that stabilizes the clot. The extrinsic pathway, triggered by tissue factor from damaged tissue, and the intrinsic pathway, triggered by contact activation, converge on factor X, leading to the conversion of prothrombin to thrombin and fibrinogen to fibrin.

Thrombin also activates additional platelets and reinforces clot stability. Fibrin strands form a cross-linked network, with factor XIII stabilizing the mesh. Vitamin K–dependent factors (II, VII, IX, X) and calcium ions are essential for proper function.

Regulation is achieved by natural anticoagulants such as antithrombin and protein C/S and by fibrinolysis, which dissolves clots via plasmin. Clinical tests include prothrombin time (PT/INR) and activated partial thromboplastin time (aPTT) to assess different parts of the cascade; D-dimer can indicate ongoing clot breakdown.

Disorders of coagulation can cause excessive bleeding (for example, hemophilia, von Willebrand disease) or thrombosis. Treatments range from managing bleeding and platelet function to anticoagulant drugs (warfarin, heparin, direct oral anticoagulants) and targeted reversal strategies when needed.