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Blood coagulation is a very delicately balanced system. When it functions as it should, the blood is maintained in a fluid state in the vasculature, yet rapidly clots to seal an injury. When hemostatic functions fail, hemorrhage or thromboembolic phenomena result. This chapter addresses molecular and biochemical features of the proteins of the coagulation system, and how they interact with cells and with one another to provide hemostasis in the living organism. We have grouped the coagulation factors as (1) the vitamin-K-dependent zymogens (prothrombin, and factors VII, IX, X, and protein C); (2) the soluble cofactors (protein S, factor V, factor VIII, and von Willebrand factor); (3) factor XI and the other “contact” factors; (4) cell-associated cofactors (tissue factor and thrombomodulin); (5) fibrinogen; (6) factor XIII and TAFI; and (7) the plasma coagulation protease inhibitors. Table 115–1 shows the major features of the coagulation factors addressed in this chapter. A model of the coagulation pathway is presented that is based on current understanding of cell–cell and cell–protein interactions that regulate hemostasis. This scheme emphasizes the importance of cellular localization and plasma protease inhibitors in confining the coagulation reactions to a specific site of vascular injury.

Table 115–1 Characteristics of Coagulation Proteins

Acronyms and Abbreviations

Acronyms and abbreviations that appear in this chapter include: ADAMTS, a disintegrin and metalloproteinase ...

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