Basic principles underlying coagulation

This chapter will discuss coagulation in the context of a hemostatic response to a break in the vasculature. Coagulation is the process that leads to fibrin formation; this process involves controlled interactions between protein coagulation factors. Hemostasis is coagulation that occurs in a physiological (as opposed to pathological) setting and results in sealing a break in the vasculature. This process has a number of components, including adhesion and activation of platelets coupled with ordered reactions of the protein coagulation factors. Hemostasis is essential to protect the integrity of the vasculature. Thrombosis is coagulation in a pathological (as opposed to physiological) setting that leads to localized intravascular clotting and potentially occlusion of a vessel. There is an overlap between the components involved in hemostasis and thrombosis, but there is also evidence to suggest that the processes of hemostasis and thrombosis have significant differences. There are also data to suggest that different vascular settings (arterial, venous, tumor microcirculation) may proceed to thrombosis by different mechanisms. Exploitation of these differences could lead to therapeutic agents that selectively target thrombosis without interfering significantly with hemostasis. Other chapters of this book will discuss some of the mechanisms behind thrombosis.