Factor VII

Definition

Factor VII is a serine protease that plays a crucial role in the initiation of the extrinsic pathway of the blood coagulation cascade. It is an essential component in the activation of the coagulation system and the formation of blood clots.

5 Must Know Facts For Your Next Test

1. Factor VII is the first serine protease activated in the extrinsic pathway of blood coagulation.
2. Activation of factor VII by tissue factor (TF) is the primary initiating event in the extrinsic pathway.
3. The factor VII-TF complex activates factor X, leading to the generation of thrombin and the formation of a fibrin clot.
4. Deficiency or impairment of factor VII can lead to prolonged bleeding and increased risk of hemorrhage.
5. Anticoagulant drugs, such as warfarin, work by inhibiting the activity of factor VII, thereby reducing the risk of thrombosis.

Review Questions

• Explain the role of factor VII in the extrinsic pathway of blood coagulation.
  • Factor VII is a crucial component of the extrinsic pathway of blood coagulation. Upon injury, tissue factor (TF) is exposed and binds to circulating factor VII, forming an active complex. This factor VII-TF complex then activates factor X, which in turn activates prothrombin to thrombin. Thrombin then converts fibrinogen to fibrin, leading to the formation of a stable blood clot. The activation of factor VII by the TF-factor VII complex is the initiating event in the extrinsic pathway, making it a critical step in the overall coagulation cascade.
• Describe the relationship between factor VII deficiency and bleeding disorders.
  • Deficiency or impairment of factor VII can lead to an increased risk of bleeding and hemorrhage. Factor VII is essential for the activation of the extrinsic pathway of coagulation, and its absence or reduced activity results in a prolonged clotting time. Individuals with factor VII deficiency may experience excessive bleeding after minor injuries, prolonged bleeding from cuts or nosebleeds, and an increased risk of internal bleeding, such as in the gastrointestinal tract or joints. The severity of the bleeding disorder is directly related to the degree of factor VII deficiency, with more severe deficiencies leading to a higher risk of life-threatening hemorrhages.
• Analyze the mechanism by which anticoagulant drugs, such as warfarin, affect factor VII and the coagulation process.
  • Anticoagulant drugs, like warfarin, work by inhibiting the activity of factor VII, thereby reducing the risk of thrombosis (blood clot formation). Warfarin and other vitamin K antagonists interfere with the synthesis of several coagulation factors, including factor VII, by inhibiting the carboxylation of glutamic acid residues in these proteins. This impairs their ability to bind to calcium and participate in the coagulation cascade. By reducing the availability and activity of factor VII, the initiation of the extrinsic pathway is disrupted, leading to a prolonged clotting time and a decreased likelihood of clot formation. This mechanism of action is crucial in the clinical use of anticoagulants for the prevention and treatment of thromboembolic disorders, such as deep vein thrombosis, pulmonary embolism, and atrial fibrillation.

Related terms

Extrinsic Pathway:

The extrinsic pathway is one of the two main pathways of blood coagulation, initiated by the exposure of tissue factor (TF) to circulating factor VII.

Tissue Factor (TF): Tissue factor is a protein expressed on the surface of certain cells, such as fibroblasts and endothelial cells, that binds to and activates factor VII, initiating the extrinsic pathway of coagulation.

Serine Protease: Serine proteases are a class of enzymes that catalyze the hydrolysis of peptide bonds, using a serine residue in their active site. Factor VII is a serine protease that activates other coagulation factors.