How does the human body prevent blood clotting in the normal vascular system?
Answers
What are the 3 stages of blood clotting?
Hemostasis has three major steps: 1) vasoconstriction, 2) temporary blockage of a break by a platelet plug, and 3) blood coagulation, or formation of a fibrin clot. These processes seal the hole until tissues are repaired.
Endothelial Surface Factors. Probably the most important factors for preventing clotting in the normal vascular system are (1) the smoothness of the endothelial cell surface, which prevents contact activation of the intrinsic clotting system; (2) a layer of glycocalyx on the endothelium (glycocalyx is a mucopolysaccharide adsorbed to the surfaces of the endothelial cells), which repels clotting factors and platelets, thereby preventing activation of clotting; and (3) a protein bound with the endothelial membrane, thrombomodulin, which binds thrombin. Not only does the binding of thrombin with thrombomodulin slow the clotting process by removing thrombin, but the thrombomod-ulin-thrombin complex also activates a plasma protein, protein C, that acts as an anticoagulant by inactivating activated Factors V and VIII.