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Questions and Answers
What is the normal bleeding time reference range for the Ivy method?
What is the normal bleeding time reference range for the Ivy method?
Which condition is associated with increased bleeding time due to abnormal platelet function?
Which condition is associated with increased bleeding time due to abnormal platelet function?
What is a major inhibitor of tissue plasminogen activator (tPA)?
What is a major inhibitor of tissue plasminogen activator (tPA)?
What can lead to a false positive result when measuring bleeding time?
What can lead to a false positive result when measuring bleeding time?
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What is the main function of α2-Antiplasmin in the fibrinolytic process?
What is the main function of α2-Antiplasmin in the fibrinolytic process?
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What is the normal reference range for the activated clotting time?
What is the normal reference range for the activated clotting time?
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What condition is caused by a deficiency in the platelet receptor IB/IX/V?
What condition is caused by a deficiency in the platelet receptor IB/IX/V?
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What is the primary function of endothelial cells in hemostasis?
What is the primary function of endothelial cells in hemostasis?
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Which method is used to assess bleeding time?
Which method is used to assess bleeding time?
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What can lead to excessive consumption of platelets?
What can lead to excessive consumption of platelets?
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What is activated by various factors like trauma and infectious agents in the context of hemostasis?
What is activated by various factors like trauma and infectious agents in the context of hemostasis?
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In the context of platelet function tests, what does a deficiency in VWF lead to?
In the context of platelet function tests, what does a deficiency in VWF lead to?
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Which test is specifically used to evaluate the Fibrinolytic Pathway?
Which test is specifically used to evaluate the Fibrinolytic Pathway?
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What impact do cytokines have on endothelial cells during hemostasis?
What impact do cytokines have on endothelial cells during hemostasis?
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What does the Ivy Method primarily assess?
What does the Ivy Method primarily assess?
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What is the primary concern of secondary hemostasis?
What is the primary concern of secondary hemostasis?
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Which condition is an example of a disease involving secondary hemostasis?
Which condition is an example of a disease involving secondary hemostasis?
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What is the effect of Thrombin activatable fibrinolysis inhibitor (TAFI)?
What is the effect of Thrombin activatable fibrinolysis inhibitor (TAFI)?
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What is measured by a bleeding time test?
What is measured by a bleeding time test?
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What should not be performed if the platelet count is below a certain level?
What should not be performed if the platelet count is below a certain level?
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What is the role of fibrinolysis?
What is the role of fibrinolysis?
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Which of the following proteins has a lower plasma concentration compared to another in the fibrinolytic system?
Which of the following proteins has a lower plasma concentration compared to another in the fibrinolytic system?
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Which phase of hemostasis involves the interplay of coagulation factors?
Which phase of hemostasis involves the interplay of coagulation factors?
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Which test detects defective platelet function?
Which test detects defective platelet function?
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What is the purpose of the fibrinolytic system?
What is the purpose of the fibrinolytic system?
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What is one of the results of the activation of prostacyclin?
What is one of the results of the activation of prostacyclin?
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What does adenosine diphosphatase primarily do?
What does adenosine diphosphatase primarily do?
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Which molecule binds to thrombin to modulate coagulation?
Which molecule binds to thrombin to modulate coagulation?
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What is the role of heparin-like molecules in coagulation?
What is the role of heparin-like molecules in coagulation?
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What is the function of tissue factor pathway inhibitor?
What is the function of tissue factor pathway inhibitor?
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What initiates platelet aggregation to form a primary hemostatic plug?
What initiates platelet aggregation to form a primary hemostatic plug?
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Which protein is deficient or missing in von Willebrand disease?
Which protein is deficient or missing in von Willebrand disease?
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What is one counterregulatory mechanism of endothelial cells?
What is one counterregulatory mechanism of endothelial cells?
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What is the requirement for activating protein C?
What is the requirement for activating protein C?
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What effect does thrombomodulin have on thrombin?
What effect does thrombomodulin have on thrombin?
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What is the primary role of Fibrinogen in the coagulation process?
What is the primary role of Fibrinogen in the coagulation process?
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How is Prothrombin activated in the coagulation cascade?
How is Prothrombin activated in the coagulation cascade?
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Which component is also known as the tissue factor in the coagulation process?
Which component is also known as the tissue factor in the coagulation process?
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What is the function of Ionized Calcium in the coagulation cascade?
What is the function of Ionized Calcium in the coagulation cascade?
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Which coagulation factor is involved in the final common pathway?
Which coagulation factor is involved in the final common pathway?
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What is the significance of Vitamin K in coagulation?
What is the significance of Vitamin K in coagulation?
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Which factor is referred to as Hageman factor?
Which factor is referred to as Hageman factor?
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What is the primary interaction needed for the activation of the prothrombin and Factor X?
What is the primary interaction needed for the activation of the prothrombin and Factor X?
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Which factor affects the amount instead of the rate of the coagulation process?
Which factor affects the amount instead of the rate of the coagulation process?
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What role does Factor V (Proaccelerin) play in coagulation?
What role does Factor V (Proaccelerin) play in coagulation?
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Study Notes
Fibrinolytic System
- Fibrinolysis is the process of breaking down fibrin, preventing excessive clotting.
- The primary proteins involved are plasmin, which degrades fibrin into fibrin degradation products.
- Inhibitors of fibrinolysis include:
- Plasminogen activator inhibitor 1 (PAI-1) which rapidly inhibits tPA and TcuPA.
- α2-Antiplasmin (α2-AP) which inactivates plasmin by forming a complex.
- Thrombin activatable fibrinolysis inhibitor (TAFI) cleaves the C-terminal lysine residues of fibrin to prevent plasminogen activation by fibrin.
Platelet Function Tests
- Measures the time taken for blood vessels constriction and platelet plug formation.
- Used to detect defective platelet function.
- A screening test for acquired and congenital platelet defects.
- Methods:
- Duke Method
- Ivy Method
- Should not be performed if platelet count is below 75,000.
- Bleeding time is measured by recording the time it takes for bleeding to stop.
- Reference range for bleeding time:
- Ivy: 1-7 minutes.
- Duke: 1-6 minutes.
- A prolonged bleeding time indicates an abnormality in platelet function which can include:
- Thrombasthenia
- Von Willebrand’s disease
- Storage pool disease
- Bernard Soulier syndrome
- Prolonged fibrinolytic states
- False positive results for bleeding time can be caused by:
- Blood pressure cuff too high.
- Incision too deep.
- Disrupting the clot with filter paper, especially frequent blotting.
- Touching the incision wound outside the tip of the blood during blotting.
Coagulation Tests
- Coagulation tests measure the time it takes for blood to clot, providing a measure of fibrin formation.
- These tests are used to assess the activity of clotting factors which can lead to the diagnosis of bleeding disorders.
- The following tests are used to assess coagulation:
- Lee-White Method
- aPTT (activated partial thromboplastin time)
- PT (prothrombin time)
- INR (international normalized ratio)
- Test for Fibrinolytic Pathway
Overview of Hemostasis
- Endothelial cells are key regulators of hemostasis by balancing antithrombotic and prothrombotic activities.
- Endothelial cell activation is triggered by:
- Trauma
- Infectious agents
- Hemodynamic forces
- Plasma mediators
- Cytokines
- Prothrombotic Properties of Endothelium:
- Prostacyclin: produced by COX-1
- Nitric Oxide: produced by eNOS
- Adenosine diphosphatase: degrades ADP
- Anticoagulant Effects of Endothelium:
- Normal endothelium shields coagulation factors from tissue factor in vessel walls
- Thrombomodulin and Endothelial Protein C Receptor bind to thrombin and protein C.
- Thrombin loses its ability to activate coagulation factor and platelets and instead cleaves and activates protein C.
- The protein C/S complex inhibits coagulation cofactors (Va and VIIIa).
- Heparin-like molecules bind and activate antithrombin III.
- Tissue Factor Pathway Inhibitor binds and inhibits tissue factor/factor VIIa complexes.
Fibrinolytic Effects of Endothelium
- tPA (tissue plasminogen activator) is synthesized by endothelium as a counterregulatory mechanism.
Coagulation Factor Groups
- Surface-Bound Proenzymes:
- Factor XII, Prekallikrein, and Factor XI (known as the “contact system”) autoactivate when associated with a negatively charged surface.
- The autoactivation of Factor XII allows for the activated partial thromboplastin time (aPTT) test.
- Vitamin K-Dependent Zymogens:
- Factor VII, Factor IX, Factor X, Factor II, and Protein C all need vitamin K for an essential carboxylation reaction.
- This carboxylation allows for the binding of these proteins to phospholipids and cell membranes where they are activated.
Stable Fibrin Clot Formation
- Secondary hemostasis is focused on platelet aggregation and stable fibrin clot formation.
- Secondary hemostasis is where the coagulation factors, like those from vitamin K-dependent zymogens, play a role in forming the stable fibrin clot.
- Glanzmann’s thrombasthenia is an example of a disease involving secondary hemostasis.
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Description
Explore the essential processes involved in the fibrinolytic system and how platelet function tests can identify defects in platelet activity. This quiz covers the mechanisms of fibrinolysis, including key proteins and inhibitors, as well as different methods for assessing platelet function. Test your knowledge on these crucial aspects of hemostasis and coagulation.
