Although there are numerous clotting factors continuously circulating within the blood system, blood is fundamentally liquid. This occurs through the bennefits of two main anticoagulant pathways.
Smooth Endothelial Lining, which prevents thrombin frombinding to the TF III within the collagen and prevents commencement of the clotting cascade.
Negatively charged ions within the preteins of the endothelial cell walls, which repel many of the similarly negatively charged platelets and clotting factors.
To learn more about the clotting cascade, please review my Clotting Cascade Page.