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Quizzes > Health & Medicine

Hemostasis Quiz: Blood Clotting and Platelet Function

Quick, free coagulation quiz to check your understanding. Instant results.

Editorial: Review CompletedCreated By: Michele LanceUpdated Aug 23, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art illustration of blood drop platelets and cells with quiz heading on sky blue background

This hemostasis quiz helps you check how blood clotting starts, strengthens, and stops bleeding, so you can review the clotting cascade and platelet function. To reinforce terms and pathways, explore the protein component of a clot, connect vessel roles with the vascular physiology quiz, and dig into platelet biology with platelets versus thrombocytes.

What is the primary purpose of hemostasis?
To break down fibrin
To transport oxygen
To increase blood pressure
To prevent blood loss by forming a clot
Hemostasis is the process that prevents blood loss at the site of injury by forming a stable clot. It involves vascular constriction, platelet plug formation, and activation of the coagulation cascade. This coordinated response stops bleeding and initiates tissue repair.
Which phase of hemostasis involves the formation of a platelet plug?
Vascular remodeling
Primary hemostasis
Fibrinolysis
Secondary hemostasis
Primary hemostasis is the initial response where platelets adhere, activate, and aggregate to form a temporary plug at the site of vessel injury. Secondary hemostasis stabilizes this plug with fibrin. Fibrinolysis and remodeling occur later to restore normal vessel patency.
What does secondary hemostasis primarily involve?
Platelet adhesion
Clot dissolution
Vasoconstriction
Fibrin clot formation through the coagulation cascade
Secondary hemostasis refers to the activation of the coagulation cascade leading to the conversion of fibrinogen into fibrin, stabilizing the platelet plug. Platelet adhesion and vasoconstriction characterize primary hemostasis. Clot dissolution occurs during fibrinolysis.
Which immediate vascular response reduces blood flow to the injury site?
Fibrinolysis
Endothelial repair
Platelet aggregation
Vascular spasm
Vascular spasm is the first response to vessel injury; the smooth muscle in the vessel wall contracts to reduce blood flow and limit blood loss. Platelet aggregation and fibrinolysis occur later in hemostasis. Endothelial repair happens during healing.
Which molecule mediates platelet adhesion to the subendothelial matrix?
Thrombin
Fibrinogen
von Willebrand factor
Plasmin
von Willebrand factor (vWF) binds to exposed collagen at injury sites and platelet glycoprotein Ib receptors, anchoring platelets to the vessel wall. Fibrinogen crosslinks platelets later, thrombin activates them, and plasmin breaks down clots.
Which ion is essential for several steps of the coagulation cascade?
Calcium (Ca2+)
Potassium (K+)
Sodium (Na+)
Magnesium (Mg2+)
Calcium ions (Ca2+) serve as cofactors for multiple enzymatic reactions in both intrinsic and extrinsic pathways of the coagulation cascade, facilitating the activation of clotting factors. Other ions like Mg2+, Na+, and K+ are not directly involved in coagulation.
What is the role of fibrinogen in hemostasis?
It mediates vasoconstriction
It is converted to fibrin to stabilize the platelet plug
It cleaves prothrombin to thrombin
It breaks down clots
Fibrinogen is a soluble plasma protein that is cleaved by thrombin to form insoluble fibrin strands, which weave through the platelet plug to stabilize and strengthen the clot. It does not directly activate thrombin, break down clots, or constrict vessels.
Which cell fragment is critical for forming the initial hemostatic plug?
Lymphocyte
Platelet
Erythrocyte
Leukocyte
Platelets are small, anucleate cell fragments derived from megakaryocytes that adhere to injury sites and aggregate to form the primary hemostatic plug. Erythrocytes, leukocytes, and lymphocytes are not directly involved in plug formation.
Which laboratory test measures the intrinsic coagulation pathway?
Bleeding time
Activated partial thromboplastin time (aPTT)
Thrombin time
Prothrombin time (PT)
aPTT assesses the intrinsic and common pathways by measuring the time it takes plasma to clot after adding an activator and phospholipid. PT measures the extrinsic pathway, bleeding time reflects platelet function, and thrombin time measures conversion of fibrinogen to fibrin.
Which test evaluates the extrinsic coagulation pathway?
Thrombin time (TT)
Platelet function assay
Prothrombin time (PT)
Activated partial thromboplastin time (aPTT)
PT measures the time for fibrin formation after adding tissue factor, evaluating the extrinsic (Factor VII) and common pathways. aPTT measures intrinsic, TT measures fibrinogen conversion, and platelet function assays evaluate platelet plug formation.
Which clotting factors depend on vitamin K for their activation?
III, IV, XI, XII
I, V, VIII, XIII
II, VII, IX, X
V, VII, VIII, X
Vitamin K is required for the gamma-carboxylation of clotting factors II (prothrombin), VII, IX, and X, which allows them to bind calcium and phospholipids. Factors I, V, VIII, XIII do not require vitamin K.
A deficiency of which factor causes Hemophilia A?
Factor VIII
Factor XI
Factor IX
Factor X
Hemophilia A is caused by a deficiency or dysfunction of Factor VIII in the intrinsic pathway, leading to prolonged aPTT. Hemophilia B involves Factor IX deficiency. Factors XI and X are involved in other disorders.
Which enzyme is primarily responsible for fibrinolysis?
Factor XIIIa
Plasmin
Thrombin
Prothrombinase
Plasmin is the key enzyme that degrades fibrin and dissolves clots during fibrinolysis. Thrombin converts fibrinogen to fibrin, Factor XIIIa crosslinks fibrin, and prothrombinase activates prothrombin.
What is the main function of thrombin in coagulation?
Inhibit platelets
Chelate calcium
Activate plasmin
Convert fibrinogen to fibrin
Thrombin cleaves fibrinogen into fibrin monomers, forming the fibrin mesh that stabilizes clots. It also activates factors V, VIII, XI, and XIII, but it does not activate plasmin, inhibit platelets, or chelate calcium.
Which test assesses platelet function and primary hemostasis?
Prothrombin time
aPTT
Bleeding time
D-dimer
Bleeding time evaluates the duration of bleeding after a standardized skin incision and reflects platelet adhesion and aggregation. PT and aPTT assess coagulation pathways, while D-dimer indicates fibrin degradation.
Which disease is characterized by a defect in von Willebrand factor?
Thrombocytopenia
Disseminated intravascular coagulation
von Willebrand disease
Hemophilia A
von Willebrand disease is due to quantitative or qualitative defects in von Willebrand factor, impairing platelet adhesion and factor VIII stabilization. Hemophilia A is a factor VIII deficiency, thrombocytopenia is low platelet count, and DIC is widespread coagulation activation.
What is the role of thrombin-activatable fibrinolysis inhibitor (TAFI)?
Attenuate fibrinolysis by removing lysine residues from fibrin
Inhibit platelet aggregation
Degrade thrombin
Activate plasminogen
TAFI is activated by thrombin and removes C-terminal lysine residues from fibrin, reducing plasminogen binding and slowing fibrinolysis. It does not activate plasminogen, degrade thrombin, or inhibit platelets.
Which lab findings are typical in disseminated intravascular coagulation (DIC)?
Low D-dimer, normal PT, high fibrinogen
Elevated platelets, short PT/aPTT
Elevated D-dimer, prolonged PT/aPTT, low fibrinogen
Normal coagulation studies and high fibrinogen
DIC features widespread coagulation activation and fibrin deposition, consuming clotting factors and platelets. This leads to elevated D-dimer from fibrin degradation, prolonged PT/aPTT, and hypofibrinogenemia.
What is the primary function of Protein C in hemostasis?
Convert fibrinogen to fibrin
Inactivate factors Va and VIIIa
Activate plasmin
Bind von Willebrand factor
Activated Protein C, with its cofactor Protein S, proteolytically inactivates factors Va and VIIIa, serving as an anticoagulant mechanism. It does not activate plasmin, convert fibrinogen, or bind vWF.
How does antithrombin III inhibit coagulation?
By forming complexes with thrombin and factor Xa
By binding von Willebrand factor
By activating Protein C
By degrading fibrin
Antithrombin III neutralizes thrombin and factor Xa (and other proteases) by forming irreversible complexes, thus preventing clot propagation. It does not activate Protein C, degrade fibrin, or interact with vWF.
Tissue factor pathway inhibitor (TFPI) primarily inhibits which complex?
Tissue factor - Factor VIIa complex
Factor VIIIa - IXa complex
Prothrombinase complex
Platelet glycoprotein IIb/IIIa
TFPI binds to and inhibits the tissue factor - Factor VIIa complex and Factor Xa, providing an early brake on the extrinsic pathway. It does not inhibit the intrinsic tenase, prothrombinase, or platelet receptors.
What is the mechanism of action of warfarin in anticoagulation?
Direct inhibition of thrombin
Inhibition of vitamin K epoxide reductase
Blockade of platelet ADP receptors
Activation of antithrombin III
Warfarin inhibits vitamin K epoxide reductase, preventing regeneration of reduced vitamin K and thus impairing gamma-carboxylation of factors II, VII, IX, and X. It does not directly inhibit thrombin, activate antithrombin, or affect ADP receptors.
Which of the following is a direct thrombin inhibitor?
Enoxaparin
Heparin
Dabigatran
Rivaroxaban
Dabigatran directly binds and inhibits thrombin (Factor IIa). Rivaroxaban is a Factor Xa inhibitor, enoxaparin is a low-molecular-weight heparin enhancing antithrombin, and unfractionated heparin also acts via antithrombin.
What is the function of Factor XIII in clot stability?
Inhibits thrombin
Activates plasminogen
Converts fibrinogen to fibrin
Crosslinks fibrin fibers to strengthen the clot
Factor XIIIa is a transglutaminase that crosslinks fibrin monomers, stabilizing and strengthening the clot mesh. It does not convert fibrinogen, activate plasminogen, or inhibit thrombin.
Which gene therapy approach is currently in clinical trials for Hemophilia A?
Retroviral integration of Factor IX gene
CRISPR-Cas9 knock-out of Factor VIII
Adeno-associated virus (AAV) vector delivering Factor VIII gene
siRNA silencing of antithrombin
AAV vectors delivering a functional Factor VIII gene are being tested in Hemophilia A patients to achieve sustained factor expression. CRISPR knockout of Factor VIII would worsen the disease, siRNA against antithrombin treats Hemophilia but not A, and Factor IX retroviral therapy targets Hemophilia B.
Which novel oral anticoagulant directly targets Factor Xa?
Heparin
Dabigatran
Apixaban
Warfarin
Apixaban is a direct, selective inhibitor of Factor Xa used orally for stroke prevention and venous thromboembolism. Dabigatran is a direct thrombin inhibitor, warfarin inhibits vitamin K recycling, and heparin acts via antithrombin.
What role do circulating microparticles play in coagulopathy during sepsis?
They degrade fibrin directly
They neutralize antithrombin III
They express tissue factor and promote thrombin generation
They inhibit fibrinolysis by binding plasmin
Microparticles released from activated or apoptotic cells during sepsis often carry tissue factor, enhancing thrombin generation and contributing to disseminated intravascular coagulation. They do not directly inhibit fibrinolysis, neutralize antithrombin, or degrade fibrin.
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Study Outcomes

  1. Understand Why Hemostasis Is Important for Blood Health and Cell Development -

    Grasp why hemostasis is important for maintaining vascular integrity, supporting overall blood health, and promoting effective blood cell development within the hematologic system.

  2. Differentiate Coagulation Pathways -

    Distinguish between the intrinsic and extrinsic coagulation pathways and their roles in initiating clot formation during the hemostasis quiz.

  3. Analyze Platelet Function -

    Analyze the stages of platelet adhesion, activation, and aggregation to reinforce key blood functions quiz concepts in preventing bleeding.

  4. Apply Hemostatic Principles -

    Apply knowledge of clotting factors and vascular responses to solve blood cell development questions and real-world hemostatic scenarios.

  5. Evaluate Hemostatic Disorders -

    Evaluate common hemostatic disorders by interpreting quiz results to identify potential abnormalities in the hematologic system.

  6. Interpret Quiz Feedback -

    Interpret your performance on the hematologic system quiz to reinforce learning outcomes and guide further study of blood functions and hemostasis.

Cheat Sheet

  1. Phases of Hemostasis -

    Hemostasis is important for maintaining vascular integrity by proceeding through vascular spasm, primary plug formation, and secondary coagulation. Primary hemostasis yields a loose platelet plug within seconds, while secondary hemostasis reinforces it with fibrin via the coagulation cascade. Use the mnemonic "VPC" (Vascular-Platelet-Coagulation) to lock the sequence in memory for your hematologic system quiz.

  2. Intrinsic vs. Extrinsic Pathways -

    The intrinsic pathway is triggered by exposed collagen and involves factors XII, XI, IX and VIII, whereas the extrinsic pathway hinges on tissue factor (factor III) and factor VII. Laboratory assessments include aPTT for the intrinsic system and PT (plus INR) for the extrinsic/common pathways; remember "aPTT for all" and "PT for the Patient's Tissue.". These fundamentals often appear on blood functions quiz questions.

  3. Platelet Activation & Aggregation -

    Upon vessel injury, von Willebrand factor mediates adhesion, platelets activate and release ADP and thromboxane A2, then aggregate to form the primary plug. A quick mnemonic is "A-D-A-P-T" (Adhesion, Degranulation, Activation, Platelet aggregation, Thromboxane) to recall each step. Solid grasp of this process will help you ace blood cell development questions in any hemostasis quiz.

  4. Hemostatic Regulation & Fibrinolysis -

    To keep clots in check, antithrombin III, protein C/S, and tissue plasminogen activator (tPA) balance coagulation by inhibiting thrombin and converting plasminogen to plasmin. Overactivation leads to bleeding, while underactivation risks thrombosis - a delicate equilibrium critical for blood health. Remember "CAP" (C-C-A: C protein, Antithrombin, Plasmin) to recall major regulators.

  5. Clinical Tests & Disorders -

    Key lab tests include bleeding time for platelet function, PT/INR for extrinsic pathway, aPTT for intrinsic pathway, and D-dimer for fibrinolysis. Prolonged aPTT suggests hemophilia A/B, while extended PT/INR can indicate warfarin effect or vitamin K deficiency. Familiarity with these assays is invaluable in a hemostasis quiz and practical clinical settings.

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