Fibrin

Fibrin is a fibrous, non-globular protein involved in the clotting of blood. It is formed by the action of the protease thrombin on fibrinogen which causes it to polymerize. The polymerized fibrin together with platelets forms a hemostatic plug or clot over a wound site.

Structure

Fibrin is made up of a linear array of repeating units, each monomer of which is made up of three chains, alpha (α), beta (β), and gamma (γ), with the gamma chain always being a homodimer. These chains are organized into a cross-linked network of fibers. The cross links are the result of the action of the enzyme factor XIII (also known as fibrin stabilizing factor), which is activated by thrombin.

Function

The primary role of fibrin is to form a clot over a damaged blood vessel wall. This clot prevents further bleeding and allows for the healing process to begin. Fibrin also binds and reduces the activity of thrombin, thereby reducing clotting, promoting clot dissolution, and limiting the size of the clot.

Clinical significance

Abnormal fibrin function or structure can result in a variety of medical conditions. These include disseminated intravascular coagulation, a condition characterized by the widespread activation of the clotting cascade and formation of fibrin clots in the small blood vessels. Other conditions include fibrinolysis, a process that prevents blood clots from growing and becoming problematic, and various forms of thrombosis.

See also

• Coagulation
• Thrombosis
• Hemostasis
• Fibrinogen
• Factor XIII

References

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  Composition of a fresh thrombus
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  Fetal thrombotic vasculopathy - high magnification
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  Genesis of Fibrin out of Fibrinogen
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  Stabilisation de la fibrine par le factor XIII
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  Fibrin