Platelets, Coagulation

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Platelets, Coagulation Haemostasis
Dr. Venkatesh M. Shashidhar. Senior Lecturer in
Pathology Fiji School of Medicine
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Platelets

• Bone marrow Megakaryocytes 10d, 4000
• Life span 7-10d, N.count 150-400x109/l
• 36 hours in spleen - 1/3 of plt in spleen
• Functions
• Hemostatic plug formation
• Coagulation factors - release, synthesis
• Surface binding sites for fibrinogen, VWF
• Surface platelet antigens, HPA1

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Hemostasis
BV Injury
Tissue Factor
Neural
Activation of Coagulation Cascade
Platelet Activation
Blood Vessel Constriction
Primary hemostatic plug
Plt-Fusion
Reduced Blood flow
Thromibn, Fibrin
Stable Hemostatic Plug
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Coagulation
Intrinsic 12,11,9,8 (aPTT)
Extrinsic-7 (PT)
Common Path (TT) FX ? FXa
Prothrombin ? Thrombin
Fibrinogen ? Fibrin
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Disorders of Hemostasis

• Vascular disorders
• Scurvy, easy bruising, Henoch-Schonlein purpura.
• Platelet disorders
• Thrombocytopenia -
• Platelet function disorders Glanzmans
• Coagulation disorders
• Congenital - Haemophilia (A, B), Von-Willebrands
• Acquired - Vitamin-K deficiency, Liver disease
• Mixed/Consumption DIC

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Coagulation Investigation
Intrinsic Path (12,11,9,8)
Extrinsic Path (7)
(PT)
(aPTT)
Common Path (10,5,2)
(TT)
Fibrinogen ? Fibrin
(FDP, Ddimer)