[Structural and functional bases of hemostasis and its pathology]

The multiphase process of blood coagulation occurs owing to the interaction of three links of hemostasis--thrombocyte apparatus, plasma factors, and vascular wall components--and is regulated by the neuro-reflectory mechanisms of the coagulating and anticoagulating systems. At the early stage of hemostasis, a set of reactions begins in the thrombocyte apparatus leading to cell aggregation, secretion of the content of granules, synthesis of prostaglandines and eventually to the formation of thrombocyte thrombus. Disorders in ultrastructures and membranes of thrombocytes, particularly in receptor glycoproteins lead to the development of molecular disease of thrombocyte and to the disturbance of hemostasis. Plasma factors are activated by some proteolysis reactions in the realization of which a great role is played by phospholipids; Ca ions and regulatory proteins. The key reaction of hemostasis is activation of prothrombin into thrombin. Hemostasis disorders at this stage are of congenital (factor deficiency) or acquired (vitamin K deficiency) nature and occur at the molecular level. Hemostasis is terminated by a step-wise formation of fibrin. Disorders of one of the stages of this process due to congenital abnormality of fibrinogen results in coagulation defect due to the molecular disease of fibrinogen. The problem of hemostasis is inseparable from that of the mechanism causing the living host resistance to thrombus formation. The regulation of the liquid state of the blood and its coagulated is performed by the combined functioning of the coagulating and anticoagulating systems.