In medicine, the clotting of blood. The process by which the blood clots to form solid masses, or clots. More than 30 types of cells and substances in blood affect clotting. The process is initiated by blood platelets. Platelets produce a substance that combines with calcium ions in the blood to form thromboplastin, which in turn converts the protein prothrombin into thrombin in a complex series of reactions. Thrombin, a proteolytic enzyme, converts fibrinogen, a protein substance, into fibrin, an insoluble protein that forms an intricate network of minute threadlike structures called fibrils and causes the blood plasma to gel. The blood cells and plasma are enmeshed in the network of fibrils to form the clot. Tissue can also be subjected to coagulation by various means, as by electrocoagulation, laser coagulation, or photocoagulation.
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1. Clotting; the process of changing from a liquid to a solid, said especially of blood ( i.e., blood c.). In vertebrates, blood c. is a result of cascade regulation from fibrin. 2. A clot or coagulum. 3. Transformation of a sol into a gel or semisolid mass; e.g., the c. of the white of an egg by means of boiling. In any colloidal suspension, the dispersion of the disperse phase from the continuous phase is greatly reduced, thereby leading to a complete or partial separation of the latter; usually an irreversible phenomenon unless the basic nature of the substance is chemically altered.
- disseminated intravascular c. (DIC) a hemorrhagic syndrome that occurs following the uncontrolled activation of clotting factors and fibrinolytic enzymes throughout small blood vessel s; fibrin is deposited, platelets and clotting factors are consumed, and fibrin degradation products inhibit fibrin polymerization, resulting in tissue necrosis and bleeding. SEE ALSO: consumption coagulopathy.

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co·ag·u·la·tion kōə-'lā-shən n
1 a) a change to a viscous, jellylike, or solid state esp a change from a liquid to a thickened curdlike state not by evaporation but by chemical reaction <the spontaneous \coagulation of freshly drawn blood> <the \coagulation of milk by rennin>
b) the process by which such change of state takes place consisting of the alteration of a soluble substance (as a protein) into an insoluble form or of the flocculation or separation of colloidal or suspended matter
2) a substance or body formed by coagulation: COAGULUM
3) disruption of tissue by physical means (as by application of an electric current) so that denaturation and clumping of protein occur <diathermic \coagulation of tissues during surgery to seal bleeding blood vessels> see electrocoagulation, photocoagulation

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the process by which a colloidal liquid changes to a jelly-like mass. See blood coagulation.

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co·ag·u·la·tion (ko-ag″u-laґshən) [L. coagulatio] 1. formation of a clot; see also blood c. 2. in colloid chemistry, the solidification of a sol into a gelatinous mass; an alteration of a disperse phase or of a dissolved solid which causes the separation of the system into a liquid phase and an insoluble mass called the clot or curd; it is usually irreversible. 3. in surgery, the disruption of tissue by physical means to form an amorphous residuum, as in electrocoagulation and photocoagulation.

Medical dictionary. 2011.

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  • coagulation — [ kɔagylasjɔ̃ ] n. f. • 1360; de coaguler ♦ Précipitation de particules en suspension dans un liquide (⇒ coagulum), causée par le chauffage, l addition d un acide ou une réaction de condensation. La coagulation du blanc d œuf, de la caséine du… …   Encyclopédie Universelle

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