(redirected from fibrinous)
Also found in: Dictionary, Thesaurus, Medical, Wikipedia.


see blood clottingblood clotting,
process by which the blood coagulates to form solid masses, or clots. In minor injuries, small oval bodies called platelets, or thrombocytes, tend to collect and form plugs in blood vessel openings.
..... Click the link for more information.



a protein of high molecular weight formed by the action of the enzyme thrombin on blood plasma fibrogen; it is composed of smooth or transversely striated fibers, agglomerations of which form the basis of the thrombus occurring when blood coagulates.

Fibrin is formed in three stages. In the first stage, two peptides A (molecular weight approximately 2,000) and two peptides B (molecular weight approximately 2,500) split off from the fibrinogen molecule by the action of thrombin, forming the fibrin monomer, which is constructed of two identical subunits joined by disulfide bonds. Each of the subunits consists of three dissimilar polypeptide chains, which are designated α, β, and γ.

In the second stage, the fibrin monomer spontaneously converts to a clot, which is called a fibrin aggregate, or nonstabilized fibrin. The aggregation of the fibrin monomer (the self-assembly of fibrin fibers) includes the transition of the molecule from the globular state to the fibrillary state. Hydrogen and electrostatic bonds and forces of hydrophobic interaction, which may be weakened in concentrated solutions of urea and other denaturing agents, participate in the formation of the fibrin aggregate. This process leads to the reconstitution of the fibrin monomer. The formation of the fibrin aggregate is accelerated by substances that carry a positive charge, such as calcium ions and protamine sulfate, and is inhibited by negatively charged compounds, such as heparin.

In the third stage the fibrin aggregate undergoes changes caused by the enzymatic action of the fibrin-stabilizing factor XIIIa, or fibrinase. Through the action of this factor, stable covalent bonds are formed between the γ- and α-polypeptide chains of fibrin-aggregate molecules, as a result of which the fibrin aggregate is stabilized as a fibrin polymer that is insoluble in concentrated solutions of urea. In cases of congenital or acquired insufficiency of factor XIIIa in the body and in certain diseases, the fibrin aggregate is not stabilized as a fibrin polymer, resulting in hemorrhagic diatheses.

Fibrin is obtained by rinsing and drying a blood clot. It is used to prepare sterile sponges and films for stopping hemorrhages from small vessels during various surgical operations.


Belitser, V. A., and T. V. Varetskaia. “Fibrinogen i fibrin: stroenie molekul, samosborka volokon.” Uspekhi sovremennoi biologii, 1975, vol. 80, issue 1(4).



The fibrous, insoluble protein that forms the structure of a blood clot; formed by the action of thrombin.


a white insoluble elastic protein formed from fibrinogen when blood clots: forms a network that traps red cells and platelets
References in periodicals archive ?
Acute fibrinous and organizing pneumonia in systemic lupus erythematosus: a case report and review of the literature.
If, however, the lipid component of pooled lysed erythrocytes is injected into the pericardial sac, a fibrinous reaction may result and fibrous or even cholesterol pericardial heart disease may develop (11).
Acute fibrinous and organizing pneumonia: a histological pattern of lung injury and possible variant of diffuse alveolar damage.
On the third postoperative day, the serous drainage from the left chest tubes began to acquire thick, fibrinous components, and loculation began to show in the left hemithorax.
The pathologic features of Histoplasma endovascular infections are notable for bland-looking fibrinous vegetations with scant inflammatory cells and absent to minimal tissue inflammatory reaction.
Postmortem findings included diffuse alveolar damage, pleural effusions, and fibrinous pericarditis.
There was a very extended fibrinous response as well as areas with cellular infiltrates (lymphocytes, macrophages, and granulocytes).
The epiglottic biopsy revealed fibrinous exudate with abundant fungal and bacterial organisms.
Regarding indications of CCPP, although gross lesions were limited to the thoracic cavity, fibrinous pleurisy (9) was not observed.
Fibrinous exudate on the visceral pericardium covered the anterior-superior right ventricular outflow tract and extended to the base of the pulmonary trunk and the right atrial appendage.
Histopathologic examination reveals the presence of periportal hepatic necrosis and severe lymphoid depletion, associated with fibrinous exudate in the spleen and fibrinous airsacculitis.
Because the patient had visible fibrinous rhinitis, a nasal and pharyngeal swab was obtained before treatment with amoxicillin was begun.