The process of blood coagulation involves two pathways: the extrinsic and intrinsic pathways (Figure 3). The cascade is dependent on a series of separate clotting factors, each of which acts as a catalyst for the next step in the system. The process results in the formation of insoluble fibrin from the soluble protein fibrinogen. This then interacts with a number of blood components, including red blood cells, to form the thrombus. Any damage to the endothelium, therefore, causes platelet aggregation and adherence to the lining of the blood-vessel walls, thereby triggering the coagulation cascade. An imbalance of this process, by increasing the rate of thrombus formation, could increase the risk of CHD, and data have shown that levels of factor VII and fibrinogen are particularly important in balancing the coagulation cascade.
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