Hemostasis: Blood coagulation and fibrinolysis - Part 3 Flashcards
What occurs, in general, in the fibrinolysis (tertiary) phase of hemostasis
Dissolution of the fibrin clot
What protein is incorporated into the developing clot which later plays a major role in degradation of the fibrin clot?
Plasminogen (inacitve)
What factors cause inactive plasminogen to become active plasmin (proteolytic)?
- Tissue plasminogen activator
- Urokinase
- Streptokinase
What factors keep inactive plasminogen inhibited?
- Plasminogen activator Inhibitory 1 & 2
- Antiplasmin (inhibits Active plasmin)
What is the role of active plasmin?
Breaks down fibrin clot into fibrin degradation products (FDP)
______ and _____ levels are raised in patients with DVT. They are estimated in clinical practice to estimate the extent and rate of _____ and in follow up patients with thrombosis.
- Fibrin degradation products (FDP)
- D-dimer
- Firbinolysis
What are D-dimer levels?
- An important fibrin degradation product
- Used in tests to estimate rate of fibrinolysis
What is the secondary hemostatic plug?
Plug broken down by plasmin into Fibrin degradation products
Chemical mediators such as ___ and ____ are released by healthy endothelium and prevent platelet aggregation.
- PGI2
- Nitric Oxide
What is the role of PGI2 in regards to platelet aggregation?
PGI2 increases cAMP levels within platelets and inhibits platelet activation.
-It is a thromboxane antagonist
Coagulation automatically initiates what?
Fibrinolysis
What are some anti-coagulation factors?
- Antithrombin III
- Protein C and S (aslo require vitamin K for gamma-carboxylation)
What is the role of Antithrombin III?
- Binds to and inhibits factor Xa and thrombin (IIa)
- Heparin acts by activating this factor and preventing coagulation.
What does Heparin activated to prevent clotting?
Antithrombin III
What are the roles of Protein C and S?
Act together to inactivate cofactors Va and VIIIa.
How is Protein C, and anti-coagulant factor, activated?
By the binding of thrombomodulin to thrombin.
What is the role of Protein S?
Cofactor for protein C
What is the role of Asprin and other COX 1 inhibitors?
prevent the formation of thromboxane in platelets. Action of aspirin on platelets is permanent.
What is the role of Heparin?
activates antithrombin III and inactivates thrombin
What is the role of Warfarin (oral anticoagulant)
blocks epoxide reductasein liver and prevents the regeneration of the active form of Vitamin K. Inhibits the synthesis of the mature vitK dependent clotting factors
What is the role of streptokinase?
thrombolytic agent; plasminogen activator; converts plasminogen to plasmin enabling the dissolution of clots.
The bleeding time test is an indicator of what?
Platelet plug formation
Prolonged bleeding time is an indicator of what?
- Low platelet count OR
- vWF deficiency OR
- Platelet receptor defects
What does the clotting time test tell you?
Time taken for the formation of the stable fibrin
Prolonged clotting time indicated defects in what?
Coagulation pathway
The bleeding time test tells you what?
Test for the time taken from the initial injury to the formation of the platelet plug
Specific defects of the intrinsic/extrinsic pathways are indicated by what?
Prothrombin time & Activated partial thromboplastin time (APTT/ PTT)
The prothrombin tiime (PT) test is also known as what?
International normalized ratio
Prothrombin time (PT) measures what?
Tests the extrinsic and the common coagulation pathways
The Prothrombin Time (PT) test measures defects in what?
- Tissue factor
- Factor VII
- Factor V
- Factor X
- Prothrombin
- Firbinogen
The partial thromboplastin time (APTT) tests what?
Intrinsic and common pathways
The Partial Thromboplastin Time (APTT) test measures defects in what?
- Factor VIII
- Factor IX
- Factor XI
- Factor XII
- Factor V
- Factor X
- Prothrombin
- Firbinogen
