Factor X

Definition

Factor X is a critical component of the blood coagulation cascade, a complex series of enzymatic reactions that lead to the formation of a fibrin clot to stop bleeding. It plays a central role in the intrinsic and extrinsic pathways of hemostasis, the physiological process that prevents excessive blood loss following injury.

5 Must Know Facts For Your Next Test

1. Factor X is also known as Stuart-Prower factor, named after the patients in whom it was first identified.
2. Activation of factor X is a critical step in the common pathway of blood coagulation, leading to the conversion of prothrombin to thrombin.
3. Factor X can be activated by either the intrinsic pathway (via factor IXa) or the extrinsic pathway (via the tissue factor-factor VIIa complex).
4. Deficiencies or abnormalities in factor X can lead to a bleeding disorder known as factor X deficiency, which is a rare inherited condition.
5. Factor X is produced in the liver and its activity is dependent on the presence of calcium ions and phospholipids.

Review Questions

• Describe the role of factor X in the blood coagulation cascade.
  • Factor X is a central component of the blood coagulation cascade, playing a crucial role in both the intrinsic and extrinsic pathways of hemostasis. It acts as a serine protease that converts prothrombin to thrombin, the active enzyme responsible for converting fibrinogen into fibrin. The formation of the fibrin mesh is the final common pathway that leads to the creation of a stable blood clot to stop bleeding. Without the activation of factor X, the coagulation cascade would be disrupted, resulting in impaired hemostasis and an increased risk of excessive bleeding.
• Explain how the activation of factor X is regulated and the consequences of factor X deficiency.
  • The activation of factor X is tightly regulated, as it is a critical step in the coagulation cascade. Factor X can be activated through the intrinsic pathway (via factor IXa) or the extrinsic pathway (via the tissue factor-factor VIIa complex). Deficiencies or abnormalities in factor X can lead to a bleeding disorder known as factor X deficiency, which is a rare inherited condition. Individuals with factor X deficiency may experience prolonged bleeding after injuries, surgeries, or even spontaneous bleeding episodes, as the coagulation cascade is impaired due to the lack of functional factor X. The severity of the bleeding symptoms can vary depending on the degree of factor X deficiency.
• Analyze the significance of the interplay between factor X, prothrombin, and thrombin in the overall process of hemostasis.
  • The interplay between factor X, prothrombin, and thrombin is crucial for the successful completion of the blood coagulation cascade and the maintenance of hemostasis. Factor X acts as a pivotal enzyme, converting the inactive prothrombin into the active thrombin. Thrombin then plays a central role in the formation of the fibrin clot by converting fibrinogen into fibrin, the insoluble protein that forms the backbone of the clot. This cascade of events, initiated by the activation of factor X, is essential for the body's ability to stop bleeding and prevent excessive blood loss following injury. Any disruption or imbalance in this delicate interplay, such as factor X deficiency, can lead to impaired hemostasis and an increased risk of bleeding disorders.

Related terms

Prothrombin:

An inactive precursor protein that is converted to the active enzyme thrombin during the coagulation cascade, leading to the formation of a fibrin clot.

Tissue Factor: A protein found on the surface of cells that initiates the extrinsic pathway of the coagulation cascade by activating factor X.

Thrombin:

The active enzyme that converts fibrinogen into fibrin, the insoluble protein that forms the backbone of a blood clot.