Coagulation - MLS 1004 - Hong Kong Metropolitan University PDF

Stages of Hemostasis Hemostasis HONG KONG METROPOLITAN Secondary Hemostasis Actions of the protein coagulation factors form fibrin in response to injury Fibrin is stabilized by Factor XIII At this time, blood has changed into a solid state Failure or deficiencies in any of the five systems involved...

Stages of Hemostasis Hemostasis HONG KONG METROPOLITAN Secondary Hemostasis Actions of the protein coagulation factors form fibrin in response to injury Fibrin is stabilized by Factor XIII At this time, blood has changed into a solid state Failure or deficiencies in any of the five systems involved with hemostasis can lead to varying degrees of uncontrolled hemorrhaging or clotting UNIVERSITY MLS 1004SEF H.LEE Hemostasis 8-2-2024 8/2/2024 LEE YC MLS 1004 SEF 1 8/2/2024 8/2/2024 LEE YC MLS 1004 SEF 2 Balance of Hemostasis 8/2/2024 LEE YC MLS 1004 SEF Stages of Hemostasis 6 8/2/2024 : hypocoagulable state OR 3 8/2/2024 LEE YC MLS 1004 SEF LEE YC MLS 1004 SEF 8/2/2024 Primary Hemostasis Process of blood clotting in response to vascular injury Blood vessels (vasculature) and platelets are the main “players.” Primary Hemostatic plug is formed Platelet plug temporarily arrests bleeding. Insoluble fibrin strands deposit on the initial plug to reinforce and stabilize. The fibrin originates from soluble plasma proteins. 1. Intrinsic Pathways - activate Factor X to Xa 2. Extrinsic Pathways - activate Factor X to Xa 3. Common Pathways - formation of fibrin clot 10 LEE YC MLS 1004 SEF LEE YC MLS 1004 SEF 14 COAGULATION SYSTEM Composed of 14 coagulation factors (serine proteases) which are interdependent (Factors I through XIII – there is no Factor VI – and PK and HMWK) ◦ Inactive form of each is an enzyme precursor which is usually designated by a Roman numeral but also given a name – e.g. Factor I fibrinogen. Numbers correspond to order of discovery NOT order in cascade. ◦ Active forms are usually designated by the letter “a” after the Roman numeral and may also have a different name – e.g. Ia Fibrin ◦ Cofactors are needed for many reactions in the cascade – e.g. Calcium, platelet factor 3 (PF3) ◦ Each molecule must be present in sufficient quantity as well as functioning normally Final product is fibrin mesh or clot which completely stops bleeding ◦ Secondary hemostasis Slow contraction or retraction and lysis of the clot occurs 11 8/2/2024 LEE YC MLS 1004 SEF 15 12 8/2/2024 LEE YC MLS 1004 SEF 16 Stages of plug formation Adhesion Secretion Aggregation Stabilization 8/2/2024 8/2/2024 Once the platelets “normal” environment is changed, they become activated or adhesive 4 LEE YC MLS 1004 SEF 13 FORMATION OF PRIMARY HEMOSTATIC PLUG Stages of Hemostasis Hemostasis Components 1. Vascular System Controls rate of blood flow 2. Platelet System Interaction of vasculature and platelets form a temporary plug 3. Coagulation System Forms a stable insoluble plug (i.e) fibrin forming 4. Fibrinolytic System Fibrin lysing 5. Coagulation Inhibition System Natural inhibitors Control fibrin formation and fibrin lysis 8/2/2024 7 LEE YC MLS 1004 SEF Composed of 3 pathways : Vascular System Following Injury thrombosis: hypercoagulable state LEE YC MLS 1004 SEF LEE YC MLS 1004 SEF 8/2/2024 COAGULATION SYSTEM Initiate hemostasis: FIRST RESPONSE Vasoconstriction of the arterioles Minimizes blood flow to injured area Prevents blood loss Delivers platelets and plasma proteins to the vessel wall Immediate Short-lived - Imbalance in one direction can lead to: 8/2/2024 9 Stages of Hemostasis - Balance of bleeding (hemorrhaging) and clotting (thrombosis) bleeding LEE YC MLS 1004 SEF Fibrinolysis Clot is removed following healing of wound Three stages of Hemostasis 1. Primary Hemostasis 2. Secondary Hemostasis 3. Fibrinolysis Heme= blood stasis= to halt Process of retaining blood within the vascular system Repairs injury to blood vessels Stops or prevents blood loss 8/2/2024 5 Hemostasis Hemostasis LEE YC MLS 1004 SEF 8 8/2/2024 LEE YC MLS 1004 SEF FIBRINOLYTIC SYSTEM Fibrin is a product formed during hemostasis, tissue repair or inflammation Once injury heals, the fibrin clot is lysed Plasmin enzymatically attacks the fibrin molecule producing fibrin degradation products (FDPs, sometimes called FSPs) that are cleared from the circulation by macrophages 8/2/2024 LEE YC MLS 1004 SEF 17 COAGULATION INHIBITION SYSTEM Function : To provides balance and control of clotting mechanisms 1. Natural inhibitors and 2. Anticoagulants Which circulate in the plasma to: Prevent clotting when it’s not needed Limit or localize the clotting that is needed Examples: Protein C and S, antithrombin III 8/2/2024 LEE YC MLS 1004 SEF 18 Laboratory Testings 1. Bleeding Time (BT) The bleeding time test is a useful tool to test for platelet plug formation and capillary integrity. 2. Prothrombin time (PT) The Prothrombin time (PT) measures functional activity of the extrinsic and common pathways. 3. Partial thromboplastin time (APTT) The Prothrombin time (PT) measures functional activity of the intrinsic and common pathways. 8/2/2024 LEE YC MLS 1004 SEF 19