17 - Hemostasis and Coagulation

Abstract

This chapter provides an overview of hemostasis and coagulation. Hemostasis, the process by which bleeding is arrested, comprises a complex series of physiological and biochemical events that terminate in the formation of a stable plug that seals the blood vessel. The process involves interaction between the blood vessel wall and platelets, blood coagulation, and fibrinolysis. The endothelium plays an important role in pathological processes, such as atherosclerosis, thrombosis, and disseminated intravascular coagulation, defective hemostasis, inflammation, immune disorders, vascular neoplasia, and metastasis. Following injury, there is increased entrapment of plasma lipoprotein components followed by proliferation of arterial smooth muscle cells and/or deposition of free cholesterol and cholesterol esters, de novo synthesis of connective tissue, and intracellular and extracellular deposition of lipids in variable amounts. On the other hand, coagulation proceeds by an intrinsic or intravascular pathway and by an extrinsic or tissue juice pathway, both of which convert prothrombin to thrombin. Most of the properties and functions of Hageman factor apply to plasma thromboplastin antecedent, which also plays an important role in the initial activation stages of coagulation.