Questions and Answers
What is Factor III more commonly known as?
Tissue Factor
What is the main function of cofactors in the clotting mechanism?
To serve as binding sites for other factors
Which factor is regulated by proteolytic cleavage?
Protein C
What is the outcome of the activation of Factor VIIa?
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What is the time it takes to form a clot in the extrinsic pathway?
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What is the trigger for the extrinsic pathway?
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What is the role of Tissue Factor in the extrinsic pathway?
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What is the sequential activation of serine proteases in the clotting cascade result in?
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What is the result of Thrombin formation in the Coagulation Cascade?
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What is the role of the intrinsic pathway in the Coagulation Cascade?
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What is the major substrate of Thrombin?
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What is the result of the conversion of fibrin monomers to fibrin clot?
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What is the role of Vitamin K in the Coagulation Cascade?
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What is the function of Factor XIII in the Coagulation Cascade?
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What is the purpose of the extrinsic pathway in the Coagulation Cascade?
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What is the function of the Vit-K dependent carboxylase?
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What is the normal value of Prothrombin Time (PT)?
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Which pathway is measured by the Partial Thromboplastin Time (PTT)?
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What is the normal value of Platelet Count?
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What is the result of a low Platelet Count?
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What is the purpose of the Coagulation Factor Assay?
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Which disease is associated with a prolonged Partial Thromboplastin Time (PTT)?
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What is the purpose of the Platelet Function Assay?
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What does the mnemonic ❗️HELPFUL stand for?
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A mutation in which proenzyme would lead to uncontrolled blood clotting?
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Which factor is directly activated by factor Xa?
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What is the primary cause of classical hemophilia A?
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Which factor is necessary for the activation of factor X by factor IXa?
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Warfarin inhibits the reduction of which vitamin?
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What is the result of an inability to form clotting factor complexes on cell membranes?
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Which factor is directly activated by factor XIa?
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What is the primary cause of the bleeding disorder in the infant?
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Why is the patient at risk for further clots?
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What is the function of Streptokinase?
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What is the role of Protein C in the body?
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Why is the liver important in hemostasis?
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What is the function of Urokinase?
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What is the effect of Warfarin on the body?
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What is the role of PAI-1 in the body?
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What is the function of t-PA in the body?
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Why is the liver important for vitamin K absorption?
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What is the effect of green leafy vegetables on Warfarin?
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Study Notes
Blood Coagulation Cascade
- Intrinsic Pathway: triggered by internal stimuli, involves serine proteases that cleave the next proenzyme in the cascade, resulting in a rapid response
- Extrinsic Pathway: triggered by trauma, involves Tissue Factor (Factor III) and Factor VII, leading to the activation of Factor X and the coagulation cascade
Factors and Cofactors
- Factor II (Prothrombin): a key factor in the coagulation cascade
- Factor III (Tissue Factor): an integral membrane protein that does not require cleavage for activation
- Factor VII: binds to Tissue Factor to auto-catalyze its activation to VIIa
- Factor X: activated by Factor VIIa, leads to the formation of Thrombin (Factor IIa)
- Calcium (Ca2+): a cofactor that facilitates the clotting mechanism
- Protein C: a regulatory protein that is activated by proteolytic cleavage and inhibits the clotting cascade
Coagulation Cascade
- Tissue Factor and VIIa: key process involved in the initiation of blood coagulation in vivo
- Steps of Extrinsic Pathway:
- Trauma causes damaged tissues to present Tissue Factor (Factor III) to blood at injured site
- Factor VII binds to Tissue Factor to auto-catalyze its activation to VIIa
- Factor VIIa activates Factor X (to Xa) and Factor IX (to IXa)
- Activation of Factor IIa (Thrombin): leads to the formation of a "soft" clot, which is then cross-linked to form a "hard and stable" fibrin clot
Vitamin K Dependence
- Factors VII, IX, X, and II: require Vitamin K for their activation
- Vitamin K-dependent carboxylase: necessary for the activation of these factors
- HELPFUL MNEMONIC: 1972 → Factor X, II
Coagulation Assays
- Coagulation Factor Assay: measures the extrinsic pathway (III, VII) and common pathway (X, V, II, I)
- Prothrombin Time (PT): measures the extrinsic pathway
- Partial Thromboplastin Time (PTT): measures the intrinsic pathway
- Platelet Function Assay: measures platelet function and counts
Pathology and Disease
- Prolonged PT and aPTT: indicative of acquired or congenital deficiency of coagulation factors, Vitamin K deficiency, or liver disease
- Hemophilia A: results from a deficiency in Factor VIII
- Hemophilia B: results from a deficiency in Factor IX
- Von Willebrand Disease: a bleeding disorder characterized by a deficiency in von Willebrand Factor (vWF)
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