Chapter 18 - Section 18.5 - Study Guide - Assess Your Learning Outcomes - Page 705: 7

The continuation of coagulation from Factor X to fibrin involves a series of steps that are collectively referred to as the common coagulation pathway. These steps lead to the conversion of soluble fibrinogen into insoluble fibrin, which forms the structural framework of the blood clot. Here are the key steps and procoagulants involved: 1. **Activation of Factor X (Factor Xa):** - Factor X (F X) is activated through the intrinsic and extrinsic pathways. It becomes Factor Xa. - The activation of Factor Xa is a critical convergence point of the coagulation pathways. 2. **Formation of Prothrombinase Complex:** - Factor Xa, along with Factor V (F Va), calcium ions, and platelet phospholipids, forms the prothrombinase complex on the surface of activated platelets. - Calcium ions are crucial for the proper assembly and function of the prothrombinase complex. 3. **Conversion of Prothrombin (Factor II) to Thrombin (Factor IIa):** - Within the prothrombinase complex, Factor Xa converts prothrombin (Factor II) to its active form, thrombin (Factor IIa). - Thrombin is a key enzyme in the coagulation cascade and has multiple functions, including the conversion of fibrinogen to fibrin. 4. **Conversion of Fibrinogen to Fibrin:** - Thrombin cleaves fibrinogen molecules to produce fibrin monomers. - Fibrin monomers are then exposed to transglutaminase enzyme (Factor XIIIa) and calcium ions. 5. **Polymerization of Fibrin:** - Fibrin monomers undergo polymerization to form long fibrin strands. This is facilitated by Factor XIIIa (activated transglutaminase). - Calcium ions play a role in promoting the cross-linking of fibrin strands. 6. **Formation of the Fibrin Mesh:** - The polymerized fibrin strands create a mesh-like structure that traps blood cells, platelets, and other components at the site of injury. - This fibrin mesh stabilizes the platelet plug and forms the basis of the blood clot. The procoagulants involved in this continuation of coagulation from Factor X to fibrin include Factor Xa, Factor V, calcium ions, platelet phospholipids, Factor II (prothrombin), and Factor XIIIa (activated transglutaminase). The culmination of these steps leads to the formation of a stable fibrin clot that seals the wound, prevents further blood loss, and provides a scaffold for tissue repair.

The continuation of coagulation from Factor X to fibrin involves a series of steps that are collectively referred to as the common coagulation pathway. These steps lead to the conversion of soluble fibrinogen into insoluble fibrin, which forms the structural framework of the blood clot. Here are the key steps and procoagulants involved: 1. **Activation of Factor X (Factor Xa):** - Factor X (F X) is activated through the intrinsic and extrinsic pathways. It becomes Factor Xa. - The activation of Factor Xa is a critical convergence point of the coagulation pathways. 2. **Formation of Prothrombinase Complex:** - Factor Xa, along with Factor V (F Va), calcium ions, and platelet phospholipids, forms the prothrombinase complex on the surface of activated platelets. - Calcium ions are crucial for the proper assembly and function of the prothrombinase complex. 3. **Conversion of Prothrombin (Factor II) to Thrombin (Factor IIa):** - Within the prothrombinase complex, Factor Xa converts prothrombin (Factor II) to its active form, thrombin (Factor IIa). - Thrombin is a key enzyme in the coagulation cascade and has multiple functions, including the conversion of fibrinogen to fibrin. 4. **Conversion of Fibrinogen to Fibrin:** - Thrombin cleaves fibrinogen molecules to produce fibrin monomers. - Fibrin monomers are then exposed to transglutaminase enzyme (Factor XIIIa) and calcium ions. 5. **Polymerization of Fibrin:** - Fibrin monomers undergo polymerization to form long fibrin strands. This is facilitated by Factor XIIIa (activated transglutaminase). - Calcium ions play a role in promoting the cross-linking of fibrin strands. 6. **Formation of the Fibrin Mesh:** - The polymerized fibrin strands create a mesh-like structure that traps blood cells, platelets, and other components at the site of injury. - This fibrin mesh stabilizes the platelet plug and forms the basis of the blood clot. The procoagulants involved in this continuation of coagulation from Factor X to fibrin include Factor Xa, Factor V, calcium ions, platelet phospholipids, Factor II (prothrombin), and Factor XIIIa (activated transglutaminase). The culmination of these steps leads to the formation of a stable fibrin clot that seals the wound, prevents further blood loss, and provides a scaffold for tissue repair.