Fibrin

Fibrin, insoluble fibrous protein that enables the blood to clot. Fibrinogen, a protein synthesized in the liver, dissolves in the blood and circulates in the body. If the body is wounded, the fibrinogen is converted by the action of the enzyme thrombin into fibrin, which builds up a spongy, fibrous network joining the edges of the wound by trapping red blood cells that form a clot to prevent further bleeding.

See also: Protein.