Excellent_hemostasis-1

Excellent_hemostasis-1 - Hemostasis and Thrombosis...

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Unformatted text preview: Hemostasis and Thrombosis Hemostasis and Thrombosis Vic Vernenkar, D.O. St. Barnabas Hospital Dept. of Surgery Normal Hemostasis Normal Hemostasis • A well regulated process • Maintains blood in a fluid, clot free state in normal vessels • Induces the rapid formation of a localized hemostatic plug at the site of vascular injury Thrombosis Thrombosis • Pathological state • Inappropriate activation of the normal hemostatic process – within the non-interrupted vascular system. • Thrombus (blood clots) formation – Blocks blood flow to vital areas Normal sequence of Hemostasis Normal sequence of Hemostasis (4 steps) • 1. Arteriolar vasoconstriction 1. Arteriolar vasoconstriction (transient) (transient) – Reflex neurogenic mechanisms – Bleeding would resume after vasoconstriction if it weren’t for the activation of platelets or coagulation systems • 2. Exposure of subendothelial ECM when 2. Exposure of subendothelial ECM when there is endothelial injury there is endothelial injury – ECM, especially collagen, is highly thrombogenic thrombogenic – Platelets adhere and become activated • Change in shape • Release of secretory products – Aggregation of platelets forms hemostatic hemostatic plug plug – This is primary hemostasis primary hemostasis First two steps First two steps of normal of normal hemostasis hemostasis Normal hemostasis continued • 3. 3. Tissue factor Tissue factor released at the site of released at the site of injury injury (by endothelial cells) – Works with secreted platelet factors – Activates coagulation cascade coagulation cascade • A series of proteins where thrombin thrombin is activated • Induces further platelet recruitment and granule release – Ends in fibrin deposition fibrin deposition – Called secondary hemostasis secondary hemostasis Normal hemostasis continued • 4. 4. Formation of permanent plug Formation of permanent plug – Prevents further hemorrhage – Polymerized fibrin and platelet aggregation – Counter regulatory mechanisms (t-PA) limit the plug to the site of the injury Steps 3 and 4 The Main Players in Hemostasis The Main Players in Hemostasis • Endothelial cells Endothelial cells • Platelets Platelets • Coagulation cascade Coagulation cascade Endothelial Cells Endothelial Cells • Produce vWF vWF (vonWillebrand factor) – A product of normal endothelium – found in the plasma – essential for platelet binding to collagen and other surfaces • Secrete Tissue factor Tissue factor – induced by cytokines (TNF, IL-1) – activates the extrinsic clotting pathway extrinsic clotting pathway Endothelial Cells have Endothelial Cells have Prothrombotic Effect Prothrombotic Effect • Via vWF and tissue factor • factors that depress fibrinolysis • factors needed for the clot are not destroyed before clot forms Collagen is highly Collagen is highly thrombogenic thrombogenic For wound healing For inflammation For hemostasis Endothelial cells have Anti-thrombotic...
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This note was uploaded on 12/27/2011 for the course STEP 1 taught by Professor Dr.aslam during the Fall '11 term at Montgomery College.

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Excellent_hemostasis-1 - Hemostasis and Thrombosis...

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