The multistep process of blood clot formation to stop bleeding is called coagulation. Blood coagulation is a process that changes circulating substances within the blood into an insoluble gel. The gel plugs leaks in blood vessels and stops the loss of blood. The process requires coagulation factors, calcium and phospholipids.
How a blood clot is made
The coagulation cascade is a complex chemical process that uses as many as 10 different proteins (called blood clotting factors or coagulation factors) found in plasma in the blood. Put simply, the clotting process changes blood from a liquid to a solid at the site of an injury.
A small tear in a blood vessel wall (for example, from a cut on the skin or an internal injury) causes bleeding.
To control blood loss the blood vessel narrows (called constriction), thus limiting blood flow through the vessel.
In response to the injury, tiny cells in the blood called platelets are activated. The platelets stick to one another and to the wound site to form a plug. The protein von Willebrand factor (VWF) helps the platelets stick to each other and to the blood vessel wall.
Next, clotting factor proteins trigger production of fibrin, a strong, strand-like substance that forms a fibrin clot, a mesh-like net that keeps the plug firm and stable. Over the next several days to weeks, the clot strengthens and then dissolves as the wounded blood vessel wall heals.
Regardless of whether the Extrinsic or Intrinsic pathway starts coagulation, completion of the process follows a common pathway. The common pathway involves the activation of factors: X, V, II, XIII and I.
The coagulation factors are numbered in the order of their discovery. There are 13 numerals but only 12 factors. Factor VI was subsequently found to be part of another factor. The following are coagulation factors and their common names:
The liver must be able to use Vitamin K to produce Factors II, VII, IX, and X.