Secondary Hemostasis
For permanent closure, the plug must be replaced by a fibrin thrombus. For this purpose, the fibrinogen (or factor I of the blood clotting cascade), which occurs in an inactive precursor in the blood, must be converted to fibrin. This requires a staggered activation of different clotting factors in the blood.
This preceding blood coagulation cascade consists of an exogenous (or extrinsic) and an endogenous (or intrinsic) pathway, which represent different activation pathways and lead to a common final pathway. The endogenous pathway includes the factors XII, XI, IX, VIII as well as calcium as the most important components. Factors III and VII as well as calcium are the most important components of the exogenous pathway.The common end section begins with the activation of factor X and the other factors V, II, XIII and I. The fibrin now activated at the end of the cascade cross-links and sticks together and is finally called the red thrombus, since the other components of the blood composition (e.g. the red blood cells) also catch into the fibrin network.
Laboratory chemical testing
The endogenous pathway can be measured in the laboratory by the so-called partial thromboplastin time PTT. The exogenous pathway is checked by the quick value or INR. Both test methods also measure the common endogenous pathway.
