What Is Normal Blood Coagulation?

Hemostasis means the arrest of the bleeding. Its function is to prevent loss of blood from the blood vessels. It depends on the mechanism of coagulation. This is counter balanced by fibrnolysis which ensures that the blood vessels are reopened in order to maintain the patency of the circulation.

Blood clotting occurs in three main stages:

1. When tissues are damaged and platelets break down, thromboplastin is released.

2. In the presence of calcium ions thromboplastin leads to the conversion of prothrombin into thrombin.

3. Thrombin is a proteolytic (protein splitting) enzyme which converts fibrinogen into fibrin.

Fibrin forms a network of long, sticky strands which entrap blood cells to establish a clot. The coagulation material contracts and exudes serum which is plasma depleted of its clotting factor.

This is the final part of a complex cascade of coagulation involving a large number of different clotting factors. It is equally important for a healthy person to maintain the blood as a fluid in order that it can circulate freely. The coagulation mechanism is normally held at bay by the presence of heparin which is produced by the liver.

Fibrinolysis is the break down of fibrin and occurs as a response to the presence of clotted blood. Unless fibrinolysis takes place, coagulation will continue.

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