Blood clotting factors

Blood clotting factors

The process of blood clotting is a sequential and very important process that occurs when there is an injury to blood vessels and tissues in the body. It is commonly called a coagulation cascade because it involves step by step events until the formation of a blood clot is achieved successfully.

There are twelve factors involved in this process, each having a specific name and function.

The blood clotting factors are:

• Fibrinogen – Factor I
• Prothrombin – Factor II
• Tissue thromboplastin – Factor III
• Calcium ions – Factor IV
• Labile factor – Factor V
• Stable factor – Factor VII
• Anti – haemophilic factor – Factor VIII
• Christmas factor – Factor IX
• Stuart – Prower factor – Factor X
• Glassman Thromboplastin Antecedent – Factor XI
• Hageman factor – Factor XII
• Fibrin stabilizing factor – Factor XIII

Fibrinogen – Factor I

Fibrinogen is synthesized in the liver has a molecular weight of 340,000 Dalton, and a half-life of about four days. It does not depend on vitamin K for its production.

When thrombin acts on fibrinogen, it is converted to fibrin which together forms strands that perform the clotting function.

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Prothrombin – Factor II

Prothrombin is also synthesized in the liver with a molecular weight of 69,000 Daltons, and a half life of 3 – 5 days. Its synthesis is dependent on the action of vitamin K.
In the presence of calcium ions; prothrombin is converted to thrombin and the latter acts on fibrinogen, converting it to fibrin.

Tissue thromboplastin – Factor III

Factor III is a lipoprotein with a high molecular weight, present in many tissues of the body but more in the brain and lungs.
Its action is also similar to calcium ions as it can also convert prothrombin to thrombin.

Calcium ions – Factor IV

Calcium has many functions in the body and its role in blood clotting is also of utmost importance; as a matter of fact, any substance that can stop or inhibit calcium ions can be used as an anticoagulant to inhibit blood clotting. It is responsible for the conversion of prothrombin to thrombin.

Labile factor – Factor V

Also known as proaccelerin, it has a molecular weight of 330, 000 Daltons, a half-life of about 12 – 36 hours and is synthesized in the liver. Labile factor plays a role in the quick conversion of prothrombin to thrombin.

Stable factor – Factor VII

Also known as proconvertin, it is a globular protein with a molecular weight of over 48,000 Daltons and a half-life of about 5 hours. It is synthesized in the liver, and its synthesis depends on vitamin K. In the extrinsic pathway of blood coagulation, proconvertin activates Stuart Prower factor (factor X).

Anti haemophilic factor – Factor VIII

Factor VIII has a very high molecular weight of over 1.2 million, and half-life of 6 – 10 hours. It is not clearly known where its synthesis occurs, and its production is independent of vitamin K.
It is very essential in the body because as the name implies, its deficiency leads to Haemophilia A.

Christmas factor – Factor IX

It has a molecular weight of 57,000 and is produced in the liver in the presence of vitamin K.
Just like stable factor does in the extrinsic pathway, Christmas factor activates Stuart Prower factor in the intrinsic pathway of blood coagulation. Deficiency of factor IX causes Haemophilia B.

Stuart – Prower factor – Factor X

Factor X has a molecular weight of 59,000, a half life of 24 – 65 hours, and is synthesized in the liver in the presence of vitamin K. It forms a common final pathway after being activated by both the intrinsic and extrinsic pathway. It is also responsible for converting prothrombin to thrombin.

Glassman Thromboplastin Antecedent – Factor XI

It is a globular protein with a molecular weight of 160,000 – 200,000 Daltons, and a half life of about 60 hours. It is produced in the liver even in the absence of Vitamin K.
In the intrinsic pathway of blood coagulation, it activates the Christmas factor (Factor IX).

Hageman factor – Factor XII

It is also a globular protein with a molecular weight of 80,000. Hageman factor is also synthesized in the liver, and its production is independent of vitamin K.
It activates factor XI in the intrinsic pathway of blood coagulation.

Fibrin stabilizing factor – Factor XIII

This is a globular protein with a high molecular weight. Factor XIII is activated by prothrombin (factor II) and upon activation stabilizes the soft clot of fibrin that has been formed, converting it into a hard clot.