What is the Difference Between Intrinsic and Extrinsic Pathways in Blood Clotting?

The blood clotting process involves three main pathways: intrinsic, extrinsic, and common. The intrinsic and extrinsic pathways are responsible for initiating the coagulation cascade, while the common pathway completes the process of clot formation.

The main differences between the intrinsic and extrinsic pathways are as follows:

• Initiation: The intrinsic pathway responds to spontaneous, internal damage of the vascular endothelium, while the extrinsic pathway becomes activated secondary to external trauma. Both pathways lead to the activation of factor X, which initiates the common pathway.
• Clotting Factors: The intrinsic pathway involves factors XII, XI, IX, and VIII, also known as Hageman factor, plasma thromboplastin antecedent, Christmas factor, and antihemophilic factor A, respectively. The extrinsic pathway involves factors VII and III, also known as proconvertin and tissue factor, respectively.
• Activation: The intrinsic pathway is activated by factors in the blood, while the extrinsic pathway is activated by tissue factor.

In summary, the intrinsic pathway is activated by factors within the blood in response to internal damage to the vascular endothelium, while the extrinsic pathway is activated by external trauma and involves tissue factor. Both pathways lead to the activation of factor X and the subsequent formation of the final blood clot.

Comparative Table: Intrinsic vs Extrinsic Pathways in Blood Clotting

The difference between the intrinsic and extrinsic pathways in blood clotting lies in the location of the bleeding and the factors that initiate the clotting process. Here is a table summarizing the differences between the two pathways:

The intrinsic pathway is triggered by internal damage to the vessel wall and involves clotting factors such as Factor XII, Factor XI, Factor IX, Factor X, and Factor VIII. On the other hand, the extrinsic pathway is initiated by external trauma, which causes blood to escape the circulation and triggers the release of tissue factor (factor III) by damaged cells outside the circulation. Both pathways eventually converge on Factor X activation, leading to the formation of a blood clot to stop the bleeding.