Mechanism of normal hemostasis

1. HEMOSTASIS
MITHUN VENUGOPAL. A
MSC MLT
HEMATOLOGY AND TRANSFUSION MEDICINE

2. WHAT IS HEMOSTASIS?
HAEM – BLOOD
STASIS – HALT/HOLD
• HOST DEFENSE MECHANISM, THAT PROTECTS THE INTEGRITY
OF VASCULAR SYSTEM AFTER TISSUE INJURY.
• IT IS A PROCESS OF FORMING A BARRIER TO THE BLOOD LOSS
AT THE INJURED SITE.

3. STAGES
1. PRIMARY HAEMOSTASIS: PLATELET PLUG FORMATION.
2. SECONDARY HAEMOSTASIS: ACTIVATION OF COAGULATION
CASCADE, DEPOSITION AND STABILIZATION OF FIBRIN.
3. FIBRINOLYSIS: DEGRADATION OF FIBRIN CLOT.

4. • FIBRIN IS FORMED BY A SERIES OF COMPLEX BIOCHEMICAL
REACTIONS FROM SOLUBLE PLASMA PROTEINS CALLED
CLOTTING FACTORS ASSOCIATED WITH INJURED BLOOD
VESSEL AND PLATELET PLUG.
• ALL PHASES ARE CONTROLLED BY INHIBITORS.

5. COMPONENTS
1. VASCULAR ENDOTHELIUM
2. PLATELETS
3. COAGULATION FACTORS
4. FIBRINOLYTIC PROTEINS

6. BV
Injury
Platelet
Activation
Platelet
Fusion
Blood Vessel
Constriction
Coagulation
Activation
Stable Hemostatic
Plug
Thromibn,
Fibrin
Reduced
Blood flow
Tissue
Factor
Neural

7. VASCULAR ENDOTHELIUM

8. • SURFACE OF ENDOTHELIUM IS NEGATIVELY CHARGED AND
REPELS CIRCULATING PLATELETS AND PROTEINS WHICH ARE
ALSO NEGATIVELY CHARGED.
• SUBSTANCES SYNTHESIZED BY ENDOTHELIAL CELLS LIKE
HEPARAN SULFATE AND THROMBOMODULIN INHIBITS THE
THROMBIN FORMATION).
NORMALLY,

9. IN ENDOTHELIAL INJURY,
• PLATELETS AND COAGULATION FACTORS ARE EXPOSED TO
SUB ENDOTHELIAL TISSUE.
• INTERACTION OF VESSEL WALL COMPONENT AND PLASMA
COMPONENTS.
• RESULTS IN THE FORMATION OF HEMOSTATIC PLUG

10. NORMAL
IN ENDOTHELIAL
INJURY

11. VASCULAR COMPONENT
VASOCONSTRICTION:
• CONSTRICTION OF BLOOD VESSEL TO MINIMIZE THE BLOOD
FLOW.
• CAUSED BY ,
- SOME NEUROGENIC FACTORS
- REGULATORY MOLECULE (SEROTONIN, THROMBOXANE)
PRODUCED BY PLATELET ACTIVATION
- ENDOTHELIN BY ENDOTHELIAL CELLS.
INCREASED VASCULAR PERMEABILITY:
• ENDOTHELIAL CONTRACTION PRODUCE GAPS THROUGH
WHICH PLASMA LEAKS OUT INTO TISSUE CAUSING

12. TISSUE THROMBOPLASTIN :
• RELEASED DURING INJURY.
• HELPS IN THE FORMATION OF FIBRIN FOR SECONDARY
HEMOSTASIS.
VON-WILLEBRANDS FACTOR:
• PRODUCED BY ENDOTHELIUM.
• SECRETED INTO THE PLASMA AND INTO THE SUB ENDOTHELIUM.
• IT BINDS WITH THE COLLAGEN FIBRES IN THE EXTRACELLULAR
MATRIX AND SUPPORTS THE BINDING OF PLATELET.

13. vWF
Resting Platelets
Platelet Adhesion

14. Vessel Wall Exposed collagen
Contraction
VFW Tissue TPL
Platelet adhesion
Activation of Coagulation
Platelet Aggregation
Thrombin
1◦ Hemostatic Plug Definitive Hemostatic Plug

15. PLATELET COMPONENTS

16. PLATELET GRANULES:
• ALPHA GRANULES
– VWF
– FIBRINOGEN
– PF4
– BETA THROMBOGLOBULIN
• DENSE GRANULES (DELTA)
– ADP
– SEROTONIN

17. PLATELET PRODUCTION
THROMBOPOIESIS/MEGAKARYOPOIESIS :
• GENERATION OF PLATELETS.
• FROM MEGAKARYOCYTE IN BONEMARROW.
• CONTROLLED BY THROMBOPOIETIN.
• NORMAL LIFE SPAN: 7-14 DAYS

19. ROLE OF PLATELETS
• INJURY – PLATELET REACT – PRIMARY HEMOSTATIC PLATELET
PLUG – BLEEDING STOPS.
• PHOSPHOLIPIDS (AGGREGATED PLATELET) – REACTION
SURFACE FOR THE FORMATION OF FIBRIN.
• SECRETION FROM PLATELET HELPS TO HEAL THE INJURED
SITE.

20. STEPS:
• WHEN INJURED, THE INACTIVE PLATELET BECOME ACTIVE AND
FORM PRIMARY PLATELET PLUG BY VARIOUS MECHANISMS
LIKE;
A) ADHESION
B) ACTIVATION
C) AGGREGATION
D) SECRETION

21. ADHESION
• FIRST STEP OF PRIMARY HEMOSTATIC PLUG FORMATION.
• DURING INJURY, PLATELET ESCAPES FROM BLOOD VESSEL AND
ATTACHES TO SUB ENDOTHELIUM.
VWF (SUB ENDOTHELIUM) – GP-1B (PLATELET)
• VWF FORMS A BRIDGE CONNECTING PLATELET TO
ENDOTHELIUM.

22. • ATTACHMENT OF MANY PLATELETS OVER THE SURFACE
FORMS A MONOLAYER.
• COVER THE INJURED SITE.
Bernard soulier syndrome – lack of gp 1b
vWD disease – lack of vWF

23. ACTIVATION
• ADHESION TRIGGERS A SERIES OF MORPHOLOGIC AND
FUNCTIONAL CHANGES KNOWN AS ACTIVATION.
CHANGES:
✔METABOLIC OR BIOCHEMICAL.
✔DUE TO SUBSTANCES PRODUCED BY PLATELET OR INJURED
ENDOTHELIUM.
✔AGONISTS – AGENTS INDUCES PLATELET ACTIVATION.
✔EACH AGONIST BINDS TO A SPECIFIC PLATELET RECEPTOR.
✔IT CAUSES A SERIES OF REACTIONS INSIDE THE PLATELET.
✔RESULTS IN THE CHANGES IN PLATELET SHAPE (PSEUDOPODS ARE
FORMED).

24. ✔INCREASES THE SURFACE AREA OF PLATELET.
✔PLATELET TO PLATELET ADHERENCE INCREASES.
✔PLATELET FIT TOGETHER.
✔ACTIVATION ALSO RESULTS IN THE FORMATION OF GP-IIB OR
GP-IIIA FOR FIBRINOGEN BINDING.
✔RECEPTORS ARE HIDDEN IN RESTING PLATELETS.
✔ACTIVATION CHANGES THE MEMBRANE SURFACE WHICH
ALLOWS FIBRIN FORMING PROTEIN (COAGULATION FACTORS)
TO BIND TO IT – PLATELET PROCOAGULANT ACTIVITY.

25. AGGREGATION
• ATTACHMENT OF PLATELET TO ONE ANOTHER.
• FREE FLOWING PLATELETS ARE ALSO ATTACHED TO THE
PLATELETS THAT ARE ADHERE TO THE COLLAGEN.
• 2 TYPES,
1. PRIMARY AGGREGATION: ADHERE LOOSELY TO ONE
ANOTHER, REVERSIBLE.
2. SECONDARY AGGREGATION: TAKES LONGER PERIOD, BEGIN
WHEN PLATELET START PRODUCING THEIR OWN AGONIST.
• FIBRINOGEN AND CALCIUM REQUIRED FOR AGGREGATION
(RELEASED BY PLATELET).
• FIBRINOGEN FORMS BRIDGE BETWEEN ADJACENT PLATELETS.

26. SECRETION
• DISCHARGE OF PLATELETS GRANULE CONTENTS INTO
SURROUNDING AREA (ADP, ATP, SEROTONIN,
THROMBOSPONDIN, ETC.)
• THE RELEASED SUBSTANCES ARE AGONISTS THAT STIMULATE
PLATELET MEMBRANE RECEPTORS.
• ALSO INCREASES THE INTERNAL CALCIUM LEVEL.

27. PRIMARY HEMOSTATIC PLUG
• EVENTUALLY PLATELET FORM A BARRIER THAT SEALS THE
INJURY – 1◦ HEMOSTATIC PLUG.
• UNSTABLE AND EASILY DISLODGED.
• STABILIZED BY 2◦ HEMOSTASIS.
• 2◦ HEMOSTASIS STARTS WITH FIBRIN FORMATION AROUND
THE PLATELET PLUG.

28. SECONDARY HEMOSTASIS
• OCCURS WHEN SOLUBLE PLASMA PROTEIN (COAGULATION
FACTORS) INTERACT IN A SERIES OF COMPLEX ENZYMATIC
REACTIONS TO CONVERT SOLUBLE FIBRINOGEN TO INSOLUBLE
FIBRIN.
• REACTIONS OCCURS IN A CASCADE.
• EACH FACTOR FIRST ACT AS A SUBSTRATE AND THEN AN
ENZYME.
• FINAL SUBSTRATE IS FIBRINOGEN ACTED UPON BY THE FINAL
ENZYME THROMBIN TO FORM FIBRIN.

29. COAGULATION FACTORS
• DESIGNATED AS ROMAN NUMBERS.
• I – XIII ACCORDING TO THE ORDER OF DISCOVERY AND NOT
BY REACTION SEQUENCE.
• FACTOR VI IS NO LONGER INCLUDED IN THE CASCADE AS IT IS
AN ACTIVATED FORM OF FACTOR V.
• ACTIVATED FACTOR – LETTER ‘A’ ACCOMPANIED THE ROMAN
NUMBER.

30. (labile factor)

31. PATHWAYS
1. INTRINSIC PATHWAY: CONTACT OF CF WITH NEGATIVELY
CHARGED SURFACE.
2. EXTRINSIC PATHWAY: CONTACT OF CF VII WITH TISSUE
FACTOR.
3. COMMON PATHWAY

33. FIBRINOLYSIS
PLASMINOGEN
PLASMIN
ACTIVATORS
Urokinase
Streptokinase
kallikrein
FIBRIN FDP
Anti plasmin
macroglobulin
INHIBITORS
PAI 1
PAI 2
PAI 3

36. REFERENCE
• SHERLYN B MCKENZIE

37. QUESTIONS???

38. THANK YOU…