Haemostasis PDF

by: UWAMAHORO Consolée (MSc in Haematology and Blood Transfusion) Objectives § Define hemostasis § Differentiate between primary and secondary hemostasis § Explain the functions of the vascular system § Discuss the physiological role of platelets in hemostasis...

by: UWAMAHORO Consolée (MSc in Haematology and Blood Transfusion) Objectives § Define hemostasis § Differentiate between primary and secondary hemostasis § Explain the functions of the vascular system § Discuss the physiological role of platelets in hemostasis. 1/27/2025 Haemostasis by UWAMAHORO 2  Objectives § List and names of coagulation factors § Discuss the physiological role of the coagulation factors in the hemostasis § Diagram and describe the intrinsic, extrinsic, and common pathway mechanisms of coagulation, including all factors involved in the reactions 1/27/2025 Haemostasis by UWAMAHORO 3 Objectives § Define fibrinolysis § Discuss the physiological role of the fibrinolytic system § List the four main components of the fibrinolytic system § Name the vitamin K dependent factors 1/27/2025 Haemostasis by UWAMAHORO 4  Introduction Haemostasis is defined as arrest of bleeding. It comes from two Greek words, ühaeme meaning blood and üstasis meaning to stop. 1/27/2025 Haemostasis by UWAMAHORO 5  Introduction Haemostasis balance is maintained in the body by complicated interactions between : ücoagulation and üthe fibrinolytic system with the actions of § platelets § vessel wall § coagulation factors 1/27/2025 Haemostasis by UWAMAHORO 6 Introduction (cnt’d) Hemostasis is the property of the circulation that maintains blood as: – a fluid within the blood vessels and – the system’s ability to form a barrier (blood clot). That clot prevents: – excessive blood loss when the vessel is traumatized, That clot will be dissolved to ensure the normal blood flow when the vessel is repaired. 1/27/2025 Haemostasis by UWAMAHORO 7 Introduction (cnt’d) Blood flows through a closed system of vessels called the circulatory system. The blood vessels and their constituents controls the physiologic functions and integrity of the circulatory system 1/27/2025 Haemostasis by UWAMAHORO 8 Introduction (cnt’d) A traumatic injury, such as: a cut to the finger/toe, severs/cuts vessels, result into bleeding. To m i n i m i z e b l o o d l o s s , t h e n o r m a l l y i n e r t circulating platelets and dissolved plasma proteins mobilize to form a clot, an insoluble mass or structural barrier (thrombus). 1/27/2025 Haemostasis by UWAMAHORO 9 Introduction (cnt’d) The clot occludes the injured vessel and prevents further loss of blood. The clot’s formation is limited to the area of injury so that normal circulation is maintained in vessels elsewhere in the body. 1/27/2025 Haemostasis by UWAMAHORO 10 Introduction (cnt’d) Briefly, control of bleeding requires rapid activation of: Øplatelets and Øplasma proteins to prevent blood loss Hemostasis also includes: vfibrin (clot) dissolution and vvessel repair. 1/27/2025 Haemostasis by UWAMAHORO 11  Components of Hemostasis vVasculature/Vessel wall vPlatelets vProteins/Coagulation factors §Fibrin-forming proteins §Fibrinolytic proteins §Inhibitors 1/27/2025 Haemostasis by UWAMAHORO 12  Clotting factors/coagulation factors Plasma proteins involved in hemostasis include: Øthose that form fibrin, Øthose that are involved with fibrinolysis, Øthose that inhibit all stages of the process. 1/27/2025 Haemostasis by UWAMAHORO 13  Stages of Hemostasis ØPrimary hemostasis ØSecondary hemostasis ØFibrinolysis 1/27/2025 Haemostasis by UWAMAHORO 14  Importants actions happening at each stage of hemostasis 1. Primary hemostasis Primary hemostatic/ Platelet Plug formation 2. Secondary hemostasis Fibrin generation 3. Fibrinolysis Breakdown of fibrin& Removal of clot 1/27/2025 Haemostasis by UWAMAHORO 15 Introduction (cnt’d) These stages are the result of interaction of: Øplatelets, Øblood vessels, and Øclotting/coagulation factors. An upset in any of the stages can result in bleeding or abnormal blood clotting (thrombosis). 1/27/2025 Haemostasis by UWAMAHORO 16  4 Primary Factors of Haemostasis Balance 4 Primary factors are blood vessels, platelets, plasma coagulation factors and fibrinolysis that maintain the balance of hemostasis between clotting and bleeding. 1/27/2025 Haemostasis by UWAMAHORO 17  During primary hemostasis, the platelets interact with the injured blood vessels. This interaction results in a mass of platelets known as the primary hemostatic plug/platelet plug, which temporarily arrests bleeding but is fragile and easily dislodged from the vessel wall. 1/27/2025 Haemostasis by UWAMAHORO 18  It involves the reinforcement of the unstable platelet plug with chemically stable fibrin. Fibrin is formed by a series of complex biochemical reactions involving soluble plasma proteins (coagulation factors) They interact with the injured blood vessels and the platelet plug. 1/27/2025 Haemostasis by UWAMAHORO 19  The fibrin-reinforced plug, or thrombus, is called the secondary hemostatic plug The insoluble strands of fibrin become deposited on and within the primary platelet plug to reinforce and stabilize it and to allow the wound to heal without further blood loss. 1/27/2025 Haemostasis by UWAMAHORO 20 § After the wound has healed, additional components of the hemostatic system break down and remove the clot to ensure the normal blood flow through the vessel. 1/27/2025 Haemostasis by UWAMAHORO 21 Fibrinolysis functions: § to remove fibrin from the vascular system in a controlled manner once it has fulfilled its hemostatic function; § to prevent excessive accumulation of fibrin. 1/27/2025 Haemostasis by UWAMAHORO 22  Excessive fibrinolysis can result in; ü bleeding; An inadequate fibrinolytic response can cause delayed lysis of a thrombus and contribute to: ü excess fibrin accumulation. 1/27/2025 Haemostasis by UWAMAHORO 23 1/27/2025 Haemostasis by UWAMAHORO 24 1/27/2025 Haemostasis by UWAMAHORO 25  In summary, hemostasis occurs because of the interaction of the blood vessels, platelets, and clotting factors. 1/27/2025 Haemostasis by UWAMAHORO 26