All the components necessary for the clotting process to proceed are found in the blood. As such, the proteins required for such clotting to take place are part of the intrinsic pathway of blood coagulation. This pathway involves a series of proteins, protein cofactors, and enzymes, which interact in reactions that take place on membrane surfaces. These reactions are initiated by tissue injury and result in the formation of a fibrin clot (Figure 1). The intrinsic pathway is initiated by the activation of factor XII by certain negatively charged surfaces, including glass. High-molecular-weight kininogen and prekallikrein are two proteins that ...(100 of 3465 words)