coagulation systems

7/24/2019 Coagulation Systems

http://slidepdf.com/reader/full/coagulation-systems 1/3

Coagulation systems•

It is the system through which coagulation factor

interact to form a fibrin clot• The fibrin forming system• Occurs in secondary hemostasis

• It’ s to reinforce the platelet plug (primaryhemostasis)

• Mediated by coagulation proteins (factors) whichnormally present in the blood in an inactive

state.

ClassificationBy hemostatic function

Substrate• fibrinogen (factor I)

Cofactors

• labile factor (factor V)• factor VIII-C (antihemophilic factor, coagulant

portion)

Enzymes• serine proteases

◦ IIa, VIIa, IXa, Xa, Xia, XIIa, prekallikrein

• transaminase•

factor XIIIa

By physical propertiesContactgroupXI, XII,Prekallikr

ein &HMWK

ProthrombingroupII, VII, IX & X

FibrinogengroupI, V, VIII &XIII

Consumed duringcoagulation

No Nobut Factor II

Yes

Present in serum Yes Yesbut Factor II

No

Present in storedplasma

Yes Yes No but FactorV and VIII

Adsorbed by BaSO4 No Yes No

Present in adsorbedplasma

Yes No Yes

Vitamin K-Dependent No Yes No

The cascade theory• Series of biochemical reactions that transforms

circulating substances into an in soluble gel

through conversion of soluble fibrinogen to fibrincirculating substances → soluble gel

soluble fibrinogen → fibrin

• Involved intrinsic and extrinsic pathways• Both of which share specific coagulation factors

with the common pathway.

Extrinsic pathway• This pathway is initiated when tissue factor (not

found in the blood) enters the vascular system.[The tissue factor includes a phospholipid component that

provides a surface for interaction of various factors]

Intrinsic pathway• All the factors necessary for clot formation are

intrinsic to the vascular compartment because it

is important in coagulation pathway•

XII, XI, VIIII, VIII

Common pathway•

X, V, II, I

Prothrombinase• The complex of activated coagulation factor X

and calcium, phospholipid, and modified factor V;

it can cleave and activate prothrombin tothrombin.

Tenase

•

These activate factor X, “IXa, VIIIa, Ca2+, PL-3” .

•

Extrinsic tenase complex is made up of tissuefactor, factor VII, and Ca2+ as an activating ion.

• Intrinsic tenase complex contains IXa, VIIIa,factor X, and they are activated by negativelycharged surfaces. These vitamin K-dependentprocoagulant factors dock to this surface through

their Gla domain with Ca2+ bridges.

coagulation systems

Documents