Chapter 18 - Section 18.5 - Study Guide - Assess Your Learning Outcomes - Page 705: 6

The intrinsic coagulation pathway is one of the two main pathways that lead to blood clot formation. It is initiated by the activation of Factor XII (Hageman factor) upon contact with negatively charged surfaces, such as exposed collagen within damaged blood vessels. Here are the key essentials of the intrinsic coagulation mechanism: **Initiation:** The intrinsic pathway is initiated when Factor XII comes into contact with negatively charged surfaces, such as collagen exposed due to vascular injury. This contact triggers the activation of Factor XII, leading to a series of reactions. **Procoagulants Involved:** 1. **Factor XII (F XII):** Factor XII, also known as Hageman factor, is the initiator of the intrinsic pathway. When activated by contact with negatively charged surfaces, it becomes Factor XIIa. 2. **Factor XI (F XI):** Factor XI is activated by Factor XIIa. The activated Factor XI (Factor XIa) plays a crucial role in the intrinsic pathway by activating Factor IX. 3. **Factor IX (F IX):** Factor IX, once activated by Factor XIa, becomes Factor IXa. Factor IXa, in combination with Factor VIIIa (activated Factor VIII), activates Factor X. 4. **Factor VIII (F VIII):** Factor VIII is a cofactor for the activation of Factor IX. It is activated in a complex process that involves the action of thrombin. 5. **Factor X (F X):** Factor X is a central component in the coagulation cascade. It is activated by both the intrinsic and extrinsic pathways. Once activated, it marks the entry into the common pathway leading to fibrin clot formation. **Convergence with the Extrinsic Pathway:** The intrinsic pathway converges with the extrinsic pathway at the activation of Factor X (Factor Xa), which is a crucial point in the coagulation cascade. **Point of Convergence:** At the point of convergence, Factor X is activated by both the extrinsic pathway (activated Factor VIIa) and the intrinsic pathway (activated Factor IXa). This activation of Factor X is a key event that leads to the formation of the common pathway of coagulation, ultimately resulting in the conversion of prothrombin to thrombin and the subsequent formation of fibrin clots. In summary, the intrinsic coagulation pathway is initiated by the activation of Factor XII upon contact with negatively charged surfaces. This pathway involves the activation of Factor XI, which in turn activates Factor IX. Factor IX, along with its cofactor Factor VIII, activates Factor X, converging with the extrinsic pathway at this point. The combined actions of the intrinsic and extrinsic pathways lead to the formation of the common pathway, culminating in the formation of fibrin clots.

The intrinsic coagulation pathway is one of the two main pathways that lead to blood clot formation. It is initiated by the activation of Factor XII (Hageman factor) upon contact with negatively charged surfaces, such as exposed collagen within damaged blood vessels. Here are the key essentials of the intrinsic coagulation mechanism: **Initiation:** The intrinsic pathway is initiated when Factor XII comes into contact with negatively charged surfaces, such as collagen exposed due to vascular injury. This contact triggers the activation of Factor XII, leading to a series of reactions. **Procoagulants Involved:** 1. **Factor XII (F XII):** Factor XII, also known as Hageman factor, is the initiator of the intrinsic pathway. When activated by contact with negatively charged surfaces, it becomes Factor XIIa. 2. **Factor XI (F XI):** Factor XI is activated by Factor XIIa. The activated Factor XI (Factor XIa) plays a crucial role in the intrinsic pathway by activating Factor IX. 3. **Factor IX (F IX):** Factor IX, once activated by Factor XIa, becomes Factor IXa. Factor IXa, in combination with Factor VIIIa (activated Factor VIII), activates Factor X. 4. **Factor VIII (F VIII):** Factor VIII is a cofactor for the activation of Factor IX. It is activated in a complex process that involves the action of thrombin. 5. **Factor X (F X):** Factor X is a central component in the coagulation cascade. It is activated by both the intrinsic and extrinsic pathways. Once activated, it marks the entry into the common pathway leading to fibrin clot formation. **Convergence with the Extrinsic Pathway:** The intrinsic pathway converges with the extrinsic pathway at the activation of Factor X (Factor Xa), which is a crucial point in the coagulation cascade. **Point of Convergence:** At the point of convergence, Factor X is activated by both the extrinsic pathway (activated Factor VIIa) and the intrinsic pathway (activated Factor IXa). This activation of Factor X is a key event that leads to the formation of the common pathway of coagulation, ultimately resulting in the conversion of prothrombin to thrombin and the subsequent formation of fibrin clots. In summary, the intrinsic coagulation pathway is initiated by the activation of Factor XII upon contact with negatively charged surfaces. This pathway involves the activation of Factor XI, which in turn activates Factor IX. Factor IX, along with its cofactor Factor VIII, activates Factor X, converging with the extrinsic pathway at this point. The combined actions of the intrinsic and extrinsic pathways lead to the formation of the common pathway, culminating in the formation of fibrin clots.