Physiology of Hemostasis - Crow

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33 Questions

What is the purpose of INR calculation?

To standardize PT results

Which of the following correlates with an ACT test?

More accurate than PTT if using a large dose of heparin

When should the ACT be measured after going on CPB?

3 minutes after going on CPB

What is the target INR for patients on warfarin?

Approximately 2-3 times more than the control

Which of the following is correct regarding a Platelet Count?

Number of platelets in the body

What is the primary role of platelets in hemostasis?

Forming a platelet plug

Which of the following best describes the initial response to blood vessel damage in hemostasis?

Vascular spasm

What is the main function of the fibrinolytic system in hemostasis?

Breaking down fibrin clots

Which of the following involves the activation of tissue factor (TF) in hemostasis?

Extrinsic pathway

What happens when there is no injury to blood vessels in terms of hemostasis?

Blood remains a liquid

In which of the following vessels are hemostatic mechanisms less effective in dealing with bleeding?


What is the main role of the cell-based prothrombinase complex?

Convert prothrombin to thrombin

Which of the following is a key function of thrombin in the coagulation process?

Convert fibrinogen to fibrin

What is the role of the Factor VIIIa/IXa complex in the coagulation cascade?

Act as a cofactor for generation of large amounts of factor Xa

What is the primary function of TFPI in the clotting process?

Neutralizes tissue factor

Which of the following is a mechanism that limits the size of a clot in the coagulation process?

Activation of plasminogen

How does the Fibrinolytic System regulate clot breakdown?

By turning off fibrinolysis when no longer needed

What is the role of Factor XIII in the clotting cascade?

Stabilizes the fibrin meshwork

Why are activated platelets considered essential for the clotting cascade?

They display receptors that bind clotting factors

What is the function of thrombin in the clotting cascade?

Activates platelets

In the classical clotting cascade, which pathway is activated when coagulation is initiated outside of the blood vessels?

Extrinsic pathway

What occurs at the endpoint of both intrinsic and extrinsic pathways in the clotting cascade?

Thrombin production

Which enzyme is synthesized in the liver and is inactive until needed to digest fibrin?


What is the role of tPA inhibitor (tPAI) in the fibrinolysis process?

Inhibits the conversion of plasminogen to plasmin

Which test assesses the intrinsic and final common pathway of coagulation?

Activated Partial Thromboplastin Time (aPTT)

What is the mechanism by which plasmin degrades fibrin?

It degrades fibrin into FDPs

Which factor must be reduced by more than 30% before a change in Prothrombin Time (PT) is observed?

Factors in the extrinsic pathway

What does Alpha-2 antiplasmin do in the context of fibrinolysis?

Inhibits the action of plasmin on fibrin

INR stands for International Normalization Ratio.


The normal value of INR is around 3.


Activated Clotting Time (ACT) is measured after heparin administration only.


Platelet Count measures the function of platelets.


ACT should be greater than 400 seconds before going on CPB.


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