The secondary hemostasis resp. plasmatic clotting

According to Morawitz you distinguish three phases:

  1. Activation phase (phase of thrombocyte activation)
  2. Coagulation phase (phase of clotting)
  3. Retraction phase (phase of wound repair)

Furthermore two systems can be differentiated: the intrinsic and the extrinsic haemostasis. Their signals have to arrive simultaneously on the level of factor X in order to enable the formation of wound plug. Thereby a various number of clotting factors come into effect, which induce in their activated form the activation of the next factor. The clotting factors are proteins, which nearly all without exception have been produced in the liver and then released into the blood. Without blood coagulation every little injury of the blood vessels would be life threatening but on the other hand clotting may not happen uncontrolled – this would lead to a plugging of the blood vessels (see also atherosclerosis) and dying of tissue. Parts of a thrombus can break away from a larger clot and cause an embolism in another organ.

Therefore many of the clotting factors circulate in an inactive pre-stage in the blood. For the most part only some of the protein have to be separated for the activation (comparable with breaking the glass of the fire detector). Therefore the active clotting factors are often proteases, enzymes which can separate a protein at a particular point of the amino acid string. Thereby one factor after another is activated in a cascade whereas every activation can be considered as a safety request.