Fibrinogenfibrin

Fibrinogenfibrin refers to the relationship between fibrinogen and fibrin in the blood coagulation system. Fibrinogen is a soluble glycoprotein produced by the liver and circulating in plasma. When vascular injury occurs, thrombin activates and cleaves fibrinopeptides A and B from the fibrinogen molecule, converting it into insoluble fibrin monomers. These monomers polymerize to form a fibrin network that, together with platelets, creates a blood clot.

The process is strengthened by factor XIIIa, which crosslinks fibrin chains to stabilize the clot. The resulting fibrin matrix traps blood cells and platelets, providing a temporary scaffold to plug the injury site. The structure and density of the fibrin network influence clot stability, permeability, and resistance to natural anticoagulant or enzymatic breakdown.

Fibrinolysis ultimately breaks down the clot. Plasmin, generated from plasminogen by tissue plasminogen activator (tPA) and other activators, degrades fibrin into soluble fragments, including D-dimers. The balance between coagulation and fibrinolysis determines clot formation and dissolution in health and disease.

Clinical relevance includes congenital and acquired disorders affecting fibrinogen or fibrin. Afibrinogenemia or hypofibrinogenemia reduces clot formation and can cause severe bleeding; dysfibrinogenemia involves dysfunctional fibrinogen with variable bleeding or thrombosis risk. Fibrinogen levels rise as an acute-phase reactant during inflammation and infection, while elevated fibrinogen is associated with cardiovascular risk. Understanding the fibrinogen-to-fibrin transition is essential for diagnosing and treating disorders of hemostasis.