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The Body Explained on Blood Clotting Pathways
Sep 6, 2025, 13:48

The Body Explained on Blood Clotting Pathways

The Body Explained shared an insightful post on X:

Blood clotting is life’s emergency repair system

When a vessel is injured, exposed endothelium and collagen trigger platelets and  clotting factors.

The cascade has 2 arms: intrinsic (contact activation) and extrinsic (tissue factor). Both converge at the common pathway to form fibrin.

  • Intrinsic pathway: Factors XII → XI → IX → VIII. This is activated by collagen and negatively charged surfaces inside vessel.
  • Extrinsic pathway: Factor VII + tissue factor (III) released from damaged endothelial cells.

Both activate Factor X, launching the common pathway.

  • Factor X + V → Prothrombin (II) → Thrombin
  • Thrombin converts Fibrinogen (I) → Fibrin mesh
  • Cross-linked by Factor XIII for clot stability.

Balance is vital:

Too little = bleeding (e.g., hemophilia, factor deficiencies)

Too much = thrombosis (MI, stroke, DVT)”

The Body Explained on Blood Clotting Pathways

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