Page 184 - Bloedstollig en bloedingsneiging

172 Bloedstolling en bloedingsneiging
Afb. XI.7
Model uit 1984 voor het bloedstollingssysteem dat de nadruk legt op activeringscom- plexen van protease-precursors51 (© Wiley-VCH; reproductie met toestemming)
Symbol conventions:
Background shading is used to indicate the surfaces that are generally functional in the coagulation process: <vertical lines> glass, kaolin or ellagic acid; <diagonal lines> thromboplastin particles or the cell surface on which tissue factor has been demonstrated; <light grey> phospholipid mixtures that contain some acidic (negatively charged) phospholipid molecules and <stippled> the external surface of the platelet membrane, or phospholipid mixtures that contain some acidic phospholipids. Protease zymogens and the derived proteases are: II (IIa), i.e. prothrombin and thrombin; X (Xa); IX (IXa); XI (XIa); XII (XIIa); and prokallikrein (kallikrein). VII is an “active zymogen”. Protein cofactors and their proteolytically modified forms are: V (Va); VIII (VIIIa), tissue factor and HMr kininogen. Protease precursors (zymogens) are shown in the complexes in which they are activated. Upon activation, dissociation of the protease product must occur followed by association with the next stage reaction components, specifically the cofactor protein, and the surface when it is different, of the next reaction stage. The final process, fibrinogen transformation to fibrin, is indicated with the “clot” represented with slight irregularity in alignment of fibrin monomer units that is meant to suggest branching of the fibrin strands such as is observed in electron photomicrographs.