HEMOSTASIS

Hemostasis

Hemostasis

a body mechanism

to stop traumatic bleeding

to prevent spontaneous bleeding

to keep the fluidity of blood

Vascular injury

tissue thromboplastin platelet adherent vaso constriction

F XII activation ADP

primary platelet aggregation

PF3 ADP 5 OH tryptamin TxA2

secondary platelet aggregation (semi permeable platelet plug) fibrin

non permeable platelet plug

Reactions in hemostatic process

Vascular reaction

primary hemostatic

barrier

Cellular reaction

Biochemical reaction / secondary

hemostatic barrier

The role of vascular in hemostasis

vaso constrictionStimulates coagulation factors and plateletsSubstances synthesized by endothelial cells:

– von Willebrand factor– tissue plasminogen activator (t-PA)– plasminogen activator inhibitor -1 (PAI-1)

– prostacyclin (PGI2)

– Thrombomodulin (PC activation)– Glycosaminoglycan (heparan sulphate,

dermatan sulphate)

Platelet

• Originated from cytoplasm of megakariocyte (fragmentation)

• Morphology : discoid, biconvex, Ǿ 2 – 4 μm• Cytoplasm contains:

granule (PF4, thromboglobulin, platelet derived growth factor, vWF, fibrinogen, F V)

Dense granule (Ca, ADP, ATP) Membrane: phospholipid bilayer, glycoprotein

(receptor)

Megakaryoblast Megakaryocytes Platelets

1/3 of platelets: stored in spleen

2/3 of plateletes: blood circulation half-lime 3-4 days

15% use daily for haemostasis normal platelet count 140-360 x 109/l

The Platelets

Morphology of platelet

The role of platelet in hemostasis

• Platelet plug formation:– Platelet adherent (need von Willebrand

Factor)– Platelet aggregation stimulated by ADP,

thrombin, thromboxan A2, epinephrine, collagen

– Platelet release reaction (from granule and dense granule)

• Stabilization of the plug : platelet factor 3 (flip flop of membrane phospholipid)

Platelet Function

phospholipid

Arachidonic acid

PGG2, PGH2

Thromboxan A2

Phospholipase A2, C

cyclooxygenase

Thromboxan synthetase

Prostacyclin

Prostacyclin synthetase

Aspirin

Coagulation Factors

Factor I Fibrinogen precursor of fibrinFactor II Prothrombin serine proteaseFactor III Tissue thrombo initiate extrinsic path. plastin Factor IV Calsium ion bridge between Gla - phospholipidFactor V Proaccelerin Cofactor of XaFactor VII Proconvertin serine proteaseFactor VIII Anti hemophilic f.Cofactor of IXa

Coagulation factors (cont)

Factor IX Christmas factor serine protease

Factor X Stuart Prower factor serine protease

Factor XI Antihemophilic C serine protease

Factor XII Hageman factor serine protease

Factor XIII Fibrin stabilizing f. transglutaminase

Prekallikrein Fletcher factor serine protease

HMW kininogen Fitzgerald factor cofactor of Kall.

Vitamin K

• Vit. K is required for carboxylation of glutamic acid → carboxy glutamate

• Vitamin K dependent protein : prothrombin, VII, IX, X, protein C, protein S, protein Z

• Deficiency of vit. K → PIVKA (protein induced by vitamin K absence or antagonist)

ResidueGlutamic acid

(GLU)

Precursor ofII, VII, IX, X

ProthrombinVII, IX, X

Residue Carboxy glutamat

(GLA)

carboxylase

Vitamin KH2

Vitamin Kepoxide

OralAnticoagulant

Negative surface Tissue thromboplastin Kal. PK HMWKXII XIIa

XI XIa VIIa VII

IX IXa Ca++

Pf 3

VIII VIIIa

X Xa Ca++

Pf3

V Va Fibrinogen

Prothrombin ThrombinFibrin monomer

Fibrin polimer

XIII XIIIa

Stabilized fibrin

Ca++

FPA

FPB+

F1.2

+

Mechanism of coagulation factor activation

Homeostatic mechanism

Local: fibrin, blood flow

Humoral:

- Antithrombin

- Protein C

- Protein S

- Heparin cofactor II

- TFPI

Cellular : liver cell, RES

Antithrombin

• Synthesized in the liver

• Function : neutralize thrombin and other serine protease (XIIa, XIa, Xa, IXa, VIIa, Kallikrein,plasmin)

• Heparin cofactor

• Activities enhanced by heparin

Function of antithrombin

Protein C and protein S

• Both are vitamin K dependent protein

• Thrombin with thrombomodulin as cofactor activates Protein C activated Protein C (APC)

• APC with Protein S as cofactor inactivates F Va and F VIIIa.

Protein C pathway

Tissue factor pathway inhibitor(TFPI)

• Function : inhibit F Xa and F VIIa

• Mechanism of action:

– First F Xa + TFPI F Xa-TFPI complex

– F Xa-TFPI complex + F VIIa-TF complex

quartener complexed

Mechanism of action of TFPI

Fibrinolytic system

Fibrinolytic system

• Fibrinolysis is a physiologic response to the Fibrinolysis is a physiologic response to the

deposition of intra or extra vascular fibrindeposition of intra or extra vascular fibrin

• Function : to destroy fibrin by enzymatic Function : to destroy fibrin by enzymatic

processprocess

• Consist of : Consist of :

– PlasminogenPlasminogen

– Plasminogen Activator Plasminogen Activator

– InhibitorInhibitor

Fibrinolytic system

Plasmin : proteolytic enzyme, substrates : fibrin, fibrinogen, V, VIII, hormon, complement

PLasminogen : proenzyme of plasmin, found in plasma and other body fluid

Plasminogen activator

Inhibitor

Plasminogen activator

Physiologic plasminogen activators:

• Tissue-type plasminogen activator (t-PA)

• Urinary- type plasminogen activator (u-PA)

Contact-phase dependent activators: F XIIa, Kallikrein

Exogen:

– Streptokinase (SK)

– Staphylokinase (SAK)

– Vampire bat plasminogen activator

Inhibitor of fibrinolysis system

Antiplasmin:

2 plasmin inhibitor

2 macroglobulin

antithrombin

1 antitrypsin

TAFI

Transamin

Plasminogen activator Plasminogen activator inhibitorinhibitor

– PAI-1PAI-1– PAI-2PAI-2– PAI-3 (?)PAI-3 (?)

Coagulation and Fibrinolytic cascade

Plasminogen Free plasminogenin clot

PAI

Plasminogen activator

Plasmin Free plasmin antiplasmin in clot

Fibrin FDP Fibrinogen FDP D dimer + F V, F VIII D dimer -

Kinin kininogen

XII

HMWK Kallikrein XI XIIa

XIa Prekallikrein

Plasminogen Plasminogen Proactivator Activator

Plasminogen Plasmin Complement system

Contact activation

XIa

IXa + VIII APC

TM

TF-VIIa Xa+V IIa Fibrin Fibrinolysis

TFPI TM TAFI