Answer :
Final answer:
The correct sequence of the clotting cascade that maintains hemostasis is: Extrinsic pathway, common pathway, intrinsic pathway. The extrinsic and intrinsic pathways converge into the common pathway, where fibrin is produced to seal the vessel.
Explanation:
The correct sequence of the clotting cascade that maintains hemostasis is:
D) Extrinsic pathway, common pathway, intrinsic pathway
The clotting cascade involves a series of reactions that lead to the formation of a blood clot. The extrinsic pathway is triggered by external trauma, while the intrinsic pathway is triggered by damage to the blood vessel wall. Both pathways converge into the common pathway, where fibrin is produced to seal off the vessel.
The clotting cascade that maintains hemostasis consists of three primary pathways: (A) the intrinsic pathway, the extrinsic pathway, and the common pathway.
The correct sequence for these pathways is as follows:
Extrinsic Pathway: This pathway is activated quickly and is triggered by external trauma that causes blood to escape the vessel. When the damaged extravascular cells come in contact with blood plasma, they release factor III (tissue factor or thromboplastin).
Factor III then activates factor VII (proconvertin) in the presence of calcium ions (Ca²+), which subsequently leads to the activation of factor X (Stuart-Prower factor). This activation of factor X initiates the common pathway.
Intrinsic Pathway: This pathway is more complex and slower than the extrinsic pathway. The intrinsic pathway begins with the activation of factor XII (Hageman factor) by contact with negatively charged surfaces, such as the inner lining of a blood vessel or foreign materials.
Following the activation of factor XI by factor XII, factor IX is activated. Factor X is activated when factor VIII and factor IX work together. As a result, the common pathway is reached by the convergence of the intrinsic and extrinsic pathways at factor X's activation.
Common Pathway: Once factor X is activated by either the intrinsic or extrinsic pathway, it forms a complex with factor V, calcium ions (Ca²+), and phospholipids to convert prothrombin (factor II) into active thrombin.
Thrombin, in turn, converts soluble fibrinogen (factor I) into insoluble fibrin strands, which form a mesh that stabilizes the platelet plug. Factor XIII then cross-links the fibrin strands to further stabilize the clot.
