Final answer:
The blood coagulation pathway encompasses the extrinsic and intrinsic pathways leading to the common pathway, culminating in the formation of a stable blood clot to prevent excessive bleeding after vascular injury.
Step-by-step explanation:
Understanding the Blood Coagulation Pathway
When a blood vessel is injured, the body initiates a sequence known as hemostasis to prevent blood loss. This involves three general steps: vascular spasm, the formation of a platelet plug, and coagulation. The process of coagulation can be activated via two mechanisms: the extrinsic pathway and the intrinsic pathway, both leading to the common pathway and resulting in clot formation.
The extrinsic pathway is initiated by external trauma to the blood vessel, releasing tissue factor (factor III) into the blood. The intrinsic pathway starts from within the bloodstream and is often activated by contact with foreign surfaces, requiring factors that are intrinsic or present within the blood. Both pathways converge into the common pathway, where factor X is activated, leading to the conversion of prothrombin to thrombin, which then transforms fibrinogen into insoluble fibrin strands, creating a stable clot.
Summary of the Coagulation Pathways
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- Extrinsic Pathway: Triggered by external tissue damage and involves factor III (tissue factor).
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- Intrinsic Pathway: Activated within the bloodstream through various factors found in the blood itself.
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- Common Pathway: Final stage where fibrin is produced to seal the injured vessel and where both extrinsic and intrinsic pathways culminate.