Transcript
Platelets, and Coagulation System
Fadel Muhammad Garishah, BSc
Thrombosis and Virchow’s Triad
Platelets • Megakaryocytes’ daughters
• Actors of primary thrombosis
• Activated and inhibited by various stimuli
• Also involved in both hemostatic and immunity-inflammation processes
Endothelial cells
• Lining of the vascular system• Possessed various adhesion molecules for the adhesion of platelets, WBCs during
thrombosis and inflammation processes
Hemostasis – Thrombosis - Fibrinolysis
http://www.hopkinsmedicine.org/hematology/coagulation.swf
Platelet Activation
Coagulation Cascade and Fibrin Polymerization
Fibrinolysis
Clinical Evaluation of Thrombosis• Clotting Time• Bleeding Time• Prothrombin Time• Activated Partial Thromboplastin Time
Bleeding time• Platelet functions to form clot• Wound in superficial area -> normally 1-9 min stops• Prolonged: platelet dysfunction, vWD, anticoagulant use,
uremia, liver failure, leukemias, MDS
Thrombin time• Assess fibrin formation in plasma• TT time < 20 seconds• Shortened: hereditary, DIC, multple myeloma
Prothrombin Time• Extrinsic factors and final common pathway• Factor II, V, VII, X• Adding Ca2+ and thromboplastin (activator) to blood sample,
and then measure the time• PT 9,5 – 13,5 seconds• INR < 1.• Prolonged PT: warfarin use, def vit K, liver disease, deficiency
of F II, VIII, V, X, DIC, fibrinogen abnormalities, heparinization
Partial Thromboplastin Time or Activated Partial Thromboplastin Time
• Intrinsic coltting factors etc• aPTT additional activator that speeds up PTT• aPTT 30-40 seconds• PTT 60 – 70 seconds• Prolonged causes: Def F VIII, IX, XI, XII,
Fitzgeralnd/prekalikrein, vWD, hypofibrinogenemia, liver cirrhosis, def vit K, , DIC, heparinization, coumarin inhibition FI, IX and X
• Shortened: early DIC, cancers, hemorrhage,
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