Presented by Dr SHARMILA G S

INTRODUCTIONCoagulation is a complex process by which

blood forms clot. It is an important part of hemostasis(the cessastion of blood loss from damaged vessels) wherein a damaged blood vessel wall is covered by a platelet and fibrin containing clot to stop bleeding and begin the repair of damaged vessels.

INTRODUCTIONWhen blood is shed out or collected in a

container,it looses its fluidity and jelly like mass after few min’s.this process is called coagulation or clotting of blood.

The clot is a mesh of thin fibrils entangling the blood cells.these fibrils consist of fibrin .the fibrin is formed from fibrinogen.

BasisBlood flows through intact vessels

Resting state is designed to keep blood flowingArteries: rapid flow. Injury requires a plug

Rapid, localised, controlled. minimise blood flow compromise

Veins: slower, intermittent flow Systemic anticoagulant clot dissolving system

Complex activating and inhibition system

Five componentsVesselsPlateletsCoagulation factors (clot forming) Coagulation inhibitors (clot controlling)Fibrinolysis (clot dissolving)

Haemostasis1. Vasoconstriction2. Platelets activated by thrombin form a

platelet plug3. Fibrin mesh forms via activation of the

coagulation system to strengthen the clot4. Clot dissolution via plasmin5. Normal blood flow past the clot

HISTORYJOHANNES MULLER(180 1-1858) described

fibrin,substance of thrombus.RUDOLF VIRCHOW(1821-1902) named

fibrinogen and it was isolated chemically by PROSPER SYLVIAN DENIS.

ALEXANDER SCHIMOIT suggested fibrinogen fibrin is a

enzymatic process and labelled hypothetical enzyme thrombin and its precurssor prothrombin

ARTHUS in 1890 discovered ca is essential for coagulation.

Platlets ---------1865 & their functions were explained by GIULIO BIZZOZERO in 1882

The theory thrombin is generated by presence of tissue factors was consolidated by PAUL MORAWITZ IN 1905

NOMENCLATUREThe usage of roman numerals rather than

eponyms or systamatic names was agreed upon during annual conferences(starting 1955)of hemostasis experts.

In 1962 consensus was achieved on the numbering of factors I-XII.

This committee evolved into the present day international committee on thrombosis and hemostasis

Assignement of numerals ceasedin 1963.

General conceptsCoagulation factors act as proteases

when activated (serine proteases)Zymogens (inactive eg fibrinogen)

converted to enzymes/proteins by limited proteolysis

Complex formation requiring calcium,phospholipid surface, cofactors

Thrombin converts fibrinogen to fibrin monomer

Fibrin monomer crosslinked to fibrinForms "glue" for platelet plug

FACTORS INVOLVED IN BLOOD CLOTTINGI FIBRINOGENII PROTHROMBINIII THROMBOPLASTINIV CALCIUMV LABILE /PROACCELERIN/ACCELATOR

GLOBULINVI presence has not been provedVII STABLE FACTORVIII ANTIHEMOPHILIC FACTOR

IX CHRISTMAS FACTORX STUART POWER FACTORXI PLASMA THROMBOPLASTIN

ANTECEDENTXII HEGMAN FACTORXIII FIBRIN STABALIZING FACTOR

I FIBRINOGENSoluble plasma protienGlobulin in natureMol.wt is 3,40,000 daltonSynthesized in liver6 polypeptide chainPlasma concen 0.3gm/100mlConverted into fibrin in the presence of

enzyme thrombin

II PROTHROMBINAlpha 2 globulin,plasma protienInactive precursor of thrombinMol.wt is 69,000daltonSynthesized in liver in the presence of vit kConcen in adult is 40mg/100ml,in new born

babies is low, lower in liver diseases

III THROMBOPLASTINTissue factorReleased by extrinsic pathway of formation of

prothrombin activator VI CALCIUM ionic calcium is essential for blood coagulation

V PROACCELERINUnstable factorRequired for formation of prothrombin

activator & thus conversion of prothrombin to thrombin in both extrinsic as well as intrinsic mech of bllod coagulation.

Is consumed during clotting hence absent in serum.

VII STABLE FACTOR/ AUTOPROTHROMBIN IStable protien synthesized in liver in the

presence of vit kRequired for activation of fac x in extrinsic

pathway.It is not consumed during clotting and

therefore present in serum as well as plasma.

VIII ANTI HEMOPHILIC FACTORProtien of beta 2 globulin synthesized in liverRequired for activation of x &formation of

prothrombin activator in intrinsic pathway.Consumed during clotting and therefore

absent from the serum.Congenital deficiency causes classical

hemophilia. Clotting time is prolonged.

IX CHRISTMAS FACTORAlso called plasma thromboplastin

component./auto prothrombin 2Protien synthesized in liver independent of

vit k.It is activated by active factor xi in the

presence of calcium.Essential for formation of prothrombin

activator in intrinsic pathway.Deficiency causes hemophilia B

X STUART POWER FACTORProtein plasma & synthesized in liverActivated by fac ix in the presence of

VIII,Ca,& phospholipids.Activated factor X along with active factor

V ,Ca, and pospholipids forms a complex called prothrombin activator in both pathways.

XI PLASMA THROMBOPLASTIN ANTECEDENTActivated by factor XII required for activation of

factor IX in the presence of calcium in intrinsic pathway.

Deficiency causes hemorrhagic state.

XII HAGEMAN FACTORIs activated to XII a when it comes in contact

wirh negatively charged surface,foreign substance or rough surface.

Its activation in the blood initiates intrinsic pathwayby activating XI to Xia

Activated factor XII also activates prekallikrein to kellikerin which in turn activates XII to XIIa(feedback activations)

XIII FIBRIN STABALIZING FACTOR

Ca2+Plasma protein stabilization

fibrin polymers

PLATLATLET PHOSPHOLIPIDS(PPL)Essential for clotting in the absence of tissue

extract

intrinsic pathway

MECHANISM OF COAGULATIONClot formation is initiated under following

situations1.Trauma to the vascular wall and adjacent

tissues2.Trauma to blood3.Contact of blood with damaged endothelial

cells or collagen or other tissue elements outside the vessel.

the process of coagulation involves a cascade of reactions in which activation of one factor leads to activation of next clotting factor.

The process can be divided into three stepsFormation of prothrombin activatorConversion of prothrombin to thrombinConversion of fibrinogen into fibrin

FORMATION OF PROTHROMBIN ACTIVATOREXTRINSIC PATHWAYINTRINSIC PATHWAY

Extrinsic PathwayExtrinsic Pathway

Tissue traumaTissue trauma

Leakage of Tissue FactorLeakage of Tissue Factor

XX XaXa

Prothrombin activatorProthrombin activator

CaCa+2+2,, factor VII factor VII

CaCa+2+2

Prothrombin Prothrombin ThrombinThrombin(factor II)(factor II)

CaCa+2+2

Intrinsic PathwayIntrinsic Pathway

Blood trauma/ contact with collagenBlood trauma/ contact with collagen

Activation of factor Activation of factor XII, IX, VIIIXII, IX, VIII

XX XaXa

CaCa+2+2

ProthrombinProthrombin activatoractivator

Prothrombin Prothrombin Thrombin Thrombin(factor II)(factor II)

Activation of certain factors (VII, II, X and protein C and S) is essential for coagulation. This activation requires vit K (reduced form)

ThrombinThrombin

FibrinogenFibrinogen Fibrin MonomersFibrin Monomers

Fibrin threadsFibrin threads

CaCa+2+2, factor XIII, factor XIII

EXTRINSIC PATHWAYIt includes following 3 basic stepsRelease of tissue thromboplastin

X XaEffect of activated factor X to form

prothrombin activator

INTRINSIC PATHWAYIT BEGINS IN THE BLOOD ITSELFActivation of factorXIIActivation of factorXIACTIVATION OF FACTOR IXActivation of factor XFormation of prothrombin activator

CONVERSION OF PROTHROMBIN TO THROMBINCaused by prothrombin activator in the

presence of calciumSurface of platelets which forms

platelet plug at the site of injuryThe rate of formation of thrombin is directly

proportional to quantity of prothrombin activator available which in turn is proportional to the degree of trauma to the vessel wall or blood

THROMBINProteolytic enzymeAmt of thrombin produced during clotting of 1ml of

blood is sufficient to coagulate 3 lt of bloodFUNCTIONSConversion of fibrinogen to fibrinPositive feedback role of thrombin accelarate the rate of formation of prothrombin

activator by activating factor VIII,V,XIII.in this way thrombin itself can cause further conversion of thrombin to prothrombin(amplification affect)

Activates protien c(anticoagulant)

Conversion of fibrinogen to fibrin1. Proteolysis Thrombin(proteolytic enzyme) removes

fibrinogen(4 low mol wt peptide chains)

fibrin monomer

2. Polymerization fibrin monomer polymerizes long fibrin threads

which forms reticulum of the clotInitially the clot is weak because the fibrin

threads are not crosslinked with each other

3. stabilization of fibrin polymersFibrin stabalizing factor (XIII) is activated by

thrombin in the presence of calcium,which causes formation of covalent crosslinkages between fibrin threads adding strength to fibrin meshwork.the fibrin meshwork trapes remaining components of plasma and blood cells to form solid mass called clot.

BLOOD CLOT RETRACTIONBlood clot meshwork of fibrin threads

blood cells platelets plasma

The fibrin threads adhere to damaged surface of blood vessels.

Clot begins to contract and squeeze out most of the fluid called serum(plasma- fibrinogen and other clotting factors)---------- 30-60mins

Platelets are essential for clot retraction. platelet thrombosthenin Actin, myosin contractile protiens present in cytoplasm of platlets causes strong

contraction of platlet spicules attached to fibrin fibres

Activated by thrombin and calcium ions

ROLE OF CALCIUM IN BLOOD COAGULATIONREQUIRED FOR PROMOTION OF ALL THE

REACTION except 1st two reactions in intrinsic pathway.

ROLE OF VITAMIN KComplex naphthoquinone deravativeSource absorbed Food bacterial flora gut

liver

ade amt of

bile salts small intestine

In liver synthesis of following factors are dependent on vit k

Coagulant like prothrombinVII,IX,XCirculatory anticoagulant protien

VITAMIN K DEFICIENCYEFFECTSProthrombin time and blood clotting time is

prolonged.CAUSESObstructive jaundiceNew born babiesChronic diarrhoeaSide effects of antibiotics

ROLE OF LIVERPlays a significant role1.Synthesis of procoagulants

V,VII,IX,X,Prothrombin &fibrinogen2.Removal of activated procoagulant3.Synthesis of anticoagulants like

heparin,antithrombin III &protein c

Liver failure causes1.Bleeding disorders due to hypocoagubility of

the blood.2.Uncontrolled extensive clotting inside the

blood vessels

Role of blood vesselsEndothelium plays both anticoagulatry as well as

coagulatory roles.Anticoagulatory roles1.Acts as a barrier between the thrombogenic

subendothelial tissue and the blood.2.Produce heparin and alpha 2 macroglobulin

which are coagulation inhibitors3.Smoothness of uninjured endothelial cells

prevents platelet aggregation4.Produce prostaglandin which opposes platelet

aggregation

Clotting mechanism1.Secreates von willebrands factor it initiates

platlet aggregation and hemostasis.2.Tissue factors released during trauma

initiates the extrinsic pathway

Subendothelial tissueCollagen fibersPlatlet aggregation is initiated when blood

comes in contact with Intrinsic coagulation pathway is initiated

when factor XII is activated.VASCULAR SMOOTH MUSCLECauses vasoconstriction initiated by

mechanical injuries to muscle.

Circulating blood does not clotVelocity of circulation constant velocity. decrease in velocity causes intravascular

clotting.Surface effects of endothelium1.Smoothness of endo lining inhibits platlet

adeshion2.A layer of glycocalyx absorbed to the inner

surface of endothelium being negatively charged repels clotting factors and platlets and thereby prevents clotting.

Intact endothelium acts as a barrier between the thrombogenic subendothelial collageneous tissue and the blood.

CIRCULATORY ANTICOAGULANTSNatural anticoagulant present in the blood

they are1.Heparin2.Antithrombin III3.Alpha 2 macroglobulin4.Protein c

Fibrinolytic mechanismProtein c is naturally occurring

anticoagulant which inactivates factor V ,VII also inactivates an inhibitor of tissue plasminogen activator increasing the formation of plasmin which acts as fibrinolytic.

Removal of activated clotting factors liver plays a important role

ANTIHEMOSTATIC MECHANISMSThe factors which balance the tendency of

the blood to clot invivo constitute the antihemostatic factors. These can be grouped as

1.Factors preventing platelet aggregation2.Factors preventing coagulation3.Factors causing fibrinolysis

Factors preventing platelet aggregationProstacyclinIs a endogenous factor which inhibit platelet

aggregation by inhibiting thromboxane A 2 formation

CIRCULATORY ANTICOAGULANTSHeparin Anti thrombin IIIPROTEIN C

anticoagulantsSubstance which delay or prevent the

coagulation of the bloodTYPESENDOGENOUSEXOGENOUSEndogenous are those present inside the body

naturallyHeparinAntithrombin IIIProtein c

Exogenous anticoagulantHeparinCalcium sequestersVitamin k antagonistDefibrination substance

HEPARINPowerful naturally acting anticoagulantFirst isolated from liverPolysaccharide containing many sulphate

groupsMol wt is 15,000-18,000 dalton SECRETIONSecreated by basophils and mast cells

Mechanism of actionPresent on luminal surface of endothelium it

acts by following mechanismPrevents of activation of prothrombin to

thrombinInhibits the action of thrombin on fibrinogen Facilitates the action of anti thrombin III ,i.e.

acts as its cofactor and thereby inhibits the active forms of clotting factors IX, X,XI,XII

Calcium sequesters/decalcyfing agentsInvitro blood clotting can be prevented by

substance which remove calcium from the blood.these include

Substance which forms insoluble salts with calcium such as sodium citrate and sodium oxalate

Calcium chelators which bind calcium such as ethylene diaminetetraacetic acid(EDTA)

Vitamin k antagonistUsed orally and thus can prevent coagulation

effectively. these includeCoumarian derivatives,e.g. dicoumarol and

warfarinMechanism of actionThese agents occupy vitamin k receptor sites in

the liver and prevent vitamin k to carry out its normal physiological functions.thus these substance inhibit synthesis of vit k dependent factor,i.e. factors VII,IX, AND X

DEFIBRINATION SUBSTANCEDestruction of fibrinogen . These includeMalaysian pit viper venom.Arvin or ancord-purified preparation of snake

venom. It is a glyco protien and is administered by injections.

COLDTemp maintained is 5-10 degree c

Inhibitors: ANTI-coagulantsAntithrombin III

Directly inactivates serine proteasesThrombin and Xa. Also: IXa and XiaPotentiated by heparin

Protein CInhibits (cleaves) the cofactors VIIIa and VaSignificantly decreases the rate of clot

formationNeeds to be activated

Protein S:Enhances activity of protein C

ThrombomodulinActivated by thrombinBinds to thrombin to alter its conformationComplex activates protein C

Tissue pathway factor inhibitorInhibits FVIIa-tissue factor complex

AnticoagulantsToo little or ineffective

Extensive clotToo much

Bleeding

TherapeuticsHeparinActivated protein CTPFI inhibitor

FibrinolysisPrevents excessive fibrin depositionAllows closely coupled with fibrin formationLocalised surface bound phenomenon that is

catalysed by fibrin formation

Components: fibrinolysisPlasminogen -> plasmin

Plasminogen activators

Inactivators of plasminogen

Inhibitors of plasmin

                                                                         

PHYSIOLOGICAL ROLE OF FIBRINOLYSIS SYSTEMPlasmin play following roleCleaning the minute clots of tiny vesselsPromote normal healing processLiquefaction of menstrual clotLiquefaction of sperms in epididymisRole in inflammatory response

TESTS FOR COAGULATIONBLEEDING TIME-the time lapse between the skin prick and

arrest of bleeding is known as bleeding time.Normal rangeBy dukes method-1-6min’sProlonged BT occurs in purpura while its

normal in hemophilia

Clotting timeThe time interval from oozing of blood after

acut or injury till the formation of clot is called clotting time

Normal range is 3-8min’sProlonged in hemophilia

XII

XI

IX

XVIII

Prothrombin (II)

thrombin

fibrinogen fibrin

STABILISED FIBRIN

V, Ca, P/L

VII

Intrinsic pathway

Extrinsic pathway

XIII

APTT

PT

Intrinsic pathway test-PTTActivated partial thromboplastin timeMax activation of contact factorsXII,XI, prekallirein,high mol.wt kinogenMore consistant and reproducableEliminates leangthy contact activation phaseNormal valuesPTT-40-100sec(>120 abnormal)aPTT-25-35sec

Time required for blood to coagulate is called PT

Performed by adding a mixture of calcium and thromboplastin to citrated plasma

As a control, a normal blood sample is tested continuously

PT ratio (PTR) = Patient’s PT Control PT

EXTRINSIC PATHWAY TEST PROTHROMBIN TIME

PROBLEMS WITH PT/PTRThromboplastins are extracts from brain,

lung or placenta of animalsThromboplastins from various manufacturers

differ in their sensitivity to prolong PTMay result in erratic control of anticoagulant

therapy

REFERENCESGuyton and hall; text book of medical

physiology-10th edition.Text book for human physiology for dental

students- indu khuranaWright (1962) “the nomen clature of blood

clotting factors” can med assoc j86 373-4 PMID 14008442

Essential of medical physiology –k sembulingam

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