Coagulation - Intrinsic and Extrinsic Pathways

The intrinsic pathway is initiated by the exposure of plasma to negatively charged surfaces, such as that provided by collagen (in vivo) or glass (in vitro). Four plasma proteins : FXII, high molecular weight kininogen (HMWK), FXI and prekallikrein (the latter two are bound to HMWK) come down on to this surface.