Recent study in the past few years has shown deficiencies are all far from simple. Several additional items, referred to as blood Factors, are also present, and these are necessary to complete the chain of reaction. To date, 13 Factors have been identified, called Factor I, Factor II, Factor III and so on. In this system, fibrinogen is also called Factor I, prothrombin is Factor II, tissue extracts Factor VII and so on.
Each Factor plays a key part, and if one is missing, then serious defects may occur.
From a practical point of view, in the bleeding diseases named haemophilia, Factor VIII is missing; in Christmas disease, Factor IX is absent. This means that the patient is subject to serious deficiencies in the normal clotting mechanism. In part this may be overcome at times of particular need (such as when surgery is necessary, or teeth must be extracted) by giving plasma with a high concentration of the missing Factor.
When a clot is formed, it will remain there for a given period of time to enable the broken vessel to heal. When healing is complete, the clot is no longer necessary. So a reverse process then sets in.
This is termed fibrinolysis (a lysis or break down of’ the insoluble fibrin clot). It is brought about by activators converting plasminogen (widely dispersed through the body) to plasmin, and this being a “proteolytic enzyme,” works on the clot to gradually break it down.
The platelets, which form part of the cellular component of the blood, are intimately involved with the clotting process. If’ a blood vessel is broken, they immediately mobilize and quickly form a soft clot at the site of injury, and effectively plug it up. But soon after this occurs, the fibrin-producing elements arc under way, and this reinforces more permanently the temporary platelet plug.
But it is a vital first-aid measure and plays an effective role in checking immediately the loss of blood.