Platelet disorders+miscellaneous Uworld key factss
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Question 1: What is the primary function of von Willebrand factor (vWF) in hemostasis?

  • Activation of platelets
  • Mediation of platelet adhesion to subendothelial collagen (correct)
  • Promotion of fibrinolysis
  • Stimulation of blood coagulation

    • Question 2: In vWF deficiency, which laboratory test measures vWF-dependent platelet agglutination?

  • Bleeding time
  • Prothrombin time (PT)
  • Ristocetin cofactor assay (correct)
  • Activated partial thromboplastin time (aPTT)

    • Question 3: How does the ristocetin cofactor assay work in diagnosing vWF deficiency?

  • It measures platelet aggregation via GP IIb/IIIa receptor interaction.
  • It measures platelet count.
  • It evaluates platelet aggregation via vWF-GP Ib receptor interaction. (correct)
  • It assesses fibrinogen levels.

    • Question 5: Which bleeding disorder is characterized by thrombocytopenia, enlarged platelets, and mucocutaneous bleeding due to a deficiency of glycoprotein Ib (GP Ib) receptors?

    <p>Bernard-Soulier syndrome</p> Signup and view all the answers

    Question 6: How does Glanzmann thrombasthenia differ from Bernard-Soulier syndrome in terms of platelet agglutination response to ristocetin?

    <p>Glanzmann thrombasthenia shows normal agglutination, while Bernard-Soulier syndrome shows abnormal agglutination.</p> Signup and view all the answers

    Question 7: What is the primary function of von Willebrand factor (vWF) in hemostasis?

    <p>Mediation of platelet adhesion to subendothelial collagen</p> Signup and view all the answers

    Question 7: Which bleeding disorder is characterized by mucocutaneous bleeding, normal platelet agglutination response to ristocetin, and deficiency of glycoprotein IIb/IIIa receptors.

    <p>b) Glanzmann thrombasthenia</p> Signup and view all the answers

    Question 8: What is the role of von Willebrand factor (vWF) in relation to factor VIII.

    <p>c) vWF carries and stabilizes factor VIII, prolonging its half-life.</p> Signup and view all the answers

    Question 9: Which treatment can be used for menorrhagia in patients with vWF deficiency.

    <p>d) Combined oral contraceptives</p> Signup and view all the answers

    Question 10: What is the primary effect of thromboxane A2 deficiency due to aspirin treatment.

    <p>a) Impaired platelet aggregation</p> Signup and view all the answers

    Question 11: In congenital deficiency of factor XII (Hageman), what is the characteristic laboratory finding.

    <p>b) Prolonged activated partial thromboplastin time (aPTT)</p> Signup and view all the answers

    Question 13: What is the primary function of ristocetin in the ristocetin cofactor assay.

    <p>a) To activate GP Ib receptors</p> Signup and view all the answers

    Question 14: Which component is responsible for platelet adhesion to subendothelial collagen after endothelial damage.

    <p>a) von Willebrand factor (vWF)</p> Signup and view all the answers

    Question 15: Which statement accurately describes the role of vWF in platelet adhesion.

    <p>d) vWF mediates platelet adhesion by binding to GP Ib receptors.</p> Signup and view all the answers

    Question 1: What is the primary reason for impaired generation of new blood cells in response to acute stressors such as blood loss or hypoxia in older individuals?

    <p>Decreased bone marrow mass &amp; Decreased response to stimulatory cytokines</p> Signup and view all the answers

    Question 2: Which of the following changes in the bone marrow composition is typically observed in older patients?

    <p>Reduced overall mass</p> Signup and view all the answers

    Question 3: In comparison to younger patients, how does the bone marrow of older patients generally respond to stimulatory cytokines?

    <p>Impaired response</p> Signup and view all the answers

    Question 4: What is the significance of increased bone marrow fat in older individuals?

    <p>It contributes to the reduced functional reserve of hematopoietic cells</p> Signup and view all the answers

    Question 5: Which factor limits the capacity of older individuals to rapidly generate new blood cells?

    <p>Impaired bone marrow reserve</p> Signup and view all the answers

    Question 8: What is the primary cause of increased medullary cavity size in patients with advanced age?

    <p>b) Loss of endosteal cortical bone</p> Signup and view all the answers

    Question 9: Which condition is characterized by anemia, extramedullary hematopoiesis (hepatosplenomegaly), and bone marrow fibrosis?

    <p>b) Myelofibrosis</p> Signup and view all the answers

    Question 10: In older individuals, what is the consequence of having a reduced overall bone marrow mass?

    <p>c) Impaired functional reserve of hematopoietic cells</p> Signup and view all the answers

    Question 11: What is the primary cause of increased medullary cavity size in patients with advanced age?

    <p>b) Loss of endosteal cortical bone</p> Signup and view all the answers

    Which cytokine stimulates the liver to increase production of thrombopoietin in infections?

    <p>Interleukin-6</p> Signup and view all the answers

    What term is used to describe the subsequent increase in serum platelet count in response to elevated thrombopoietin levels during infections?

    <p>Reactive thrombocytosis</p> Signup and view all the answers

    Which condition is most likely to cause elevated platelet count due to the release of inflammatory cytokines?

    <p>Reactive thrombocytosis</p> Signup and view all the answers

    What is the role of hepcidin in the context of elevated inflammatory cytokine levels?

    <p>It down-regulates iron absorption and iron release.</p> Signup and view all the answers

    Which term is used to describe the anemia characterized by reduced iron availability for reticulocytosis due to inflammatory cytokine-induced hepcidin release?

    <p>Microcytic anemia</p> Signup and view all the answers

    Question 7: What is the primary cause of reactive thrombocytosis in the setting of infections?

    <p>High levels of interleukin-6 (IL-6)</p> Signup and view all the answers

    Question 8: Which condition leads to increased erythrocytosis?

    <p>Chronic hypoxemia</p> Signup and view all the answers

    Question 9: Which of the following terms describes a state of elevated platelet count due to ongoing infection or inflammation?

    <p>Reactive thrombocytosis</p> Signup and view all the answers

    Question 10: What is the most common cause of elevated platelet count in various age groups?

    <p>Reactive thrombocytosis</p> Signup and view all the answers

    Question 11: What is the primary cause of essential thrombocythemia?

    <p>None</p> Signup and view all the answers

    Question 1: What is the likely cause of exertional dyspnea, fatigue, conjunctival pallor, macrocytosis, and hypersegmented neutrophils?

    <p>Vitamin B12 deficiency</p> Signup and view all the answers

    Question 2: Which vitamin acts as a cofactor in the recycling of 5-methyl-tetrahydrofolate to tetrahydrofolate?

    <p>Vitamin B12 (cobalamin)</p> Signup and view all the answers

    Question 3: Why are hematopoietic cells primarily affected in megaloblastic anemia due to vitamin B12 deficiency?

    <p>Their low replication rate</p> Signup and view all the answers

    Question 4: What is the primary impact of folate or vitamin B12 deficiency on DNA synthesis and cell cycle progression?

    <p>Impaired S-phase progression</p> Signup and view all the answers

    Question 5: What term describes the condition in which nuclear division slows relative to cytoplasmic maturation?

    <p>Megaloblastic anemia</p> Signup and view all the answers

    Question 6: Which of the following complications is more likely to be associated with vitamin B12 deficiency rather than folate deficiency?

    <p>Symmetric paresthesia</p> Signup and view all the answers

    Question 7: What term is used to describe the condition marked by the destruction of hematopoietic stem cells and replacement of bone marrow with fat cells?

    <p>Aplastic anemia</p> Signup and view all the answers

    Question 8: What would be a distinguishing feature on peripheral blood smear in megaloblastic anemia due to vitamin B12 deficiency?

    <p>Nucleated red blood cells</p> Signup and view all the answers

    Question 9: Which laboratory finding is characteristic of chronic kidney disease, rather than megaloblastic anemia?

    <p>Normocytic anemia</p> Signup and view all the answers

    Question 10: What condition typically causes traumatic hemolysis due to red blood cell shearing, resulting in schistocytes on peripheral blood smear?

    <p>Aortic stenosis</p> Signup and view all the answers

    Which one of these is the major form of hemoglobin in adults?

    <p>2 alpha and 2 beta chains</p> Signup and view all the answers

    Which protein is primarily responsible for oxygen storage in skeletal and cardiac muscle tissue?

    <p>Myoglobin</p> Signup and view all the answers

    What shape is the oxygen-hemoglobin dissociation curve for myoglobin?

    <p>Hyperbolic</p> Signup and view all the answers

    Question 7: What is the main difference between the oxygen-hemoglobin dissociation curve of hemoglobin A and that of individual hemoglobin subunits?

    <p>Individual subunits have a hyperbolic curve, while hemoglobin A has a sigmoidal curve</p> Signup and view all the answers

    Question 8: Which factor would cause the oxygen-hemoglobin dissociation curve to shift to the right.

    <p>A low oxygen affinity hemoglobin</p> Signup and view all the answers

    Question 9: A left shift in the oxygen-hemoglobin dissociation curve indicates:

    <p>A high oxygen affinity hemoglobin</p> Signup and view all the answers

    Question 10: Which one of these is the most correct?

    <p>They share a similar primary structure but have different secondary and tertiary structures</p> Signup and view all the answers

    Question 11: Which one of these is the most correct about hemoglobin and myoglobin?

    <p>They have almost identical secondary and tertiary structures</p> Signup and view all the answers

    Which enzyme is primarily inhibited by aspirin when administered in low doses, resulting in a sustained decrease in thromboxane A2 production and subsequent antithrombotic effects?

    <p>COX-1</p> Signup and view all the answers

    What is the mechanism by which aspirin achieves its prolonged antithrombotic effect when administered in low doses?

    <p>Irreversible acetylation and inhibition of COX-1</p> Signup and view all the answers

    What is the main product of COX-2 enzyme activity, which is inducibly expressed and contributes to fever, inflammation, and pain sensitivity?

    <p>Prostaglandins</p> Signup and view all the answers

    Aspirin inhibits COX-1 by:

    <p>Irreversible acetylation</p> Signup and view all the answers

    Why is aspirin unique compared to other NSAIDs in terms of its effect on platelet function?

    <p>Reducing platelet aggregation</p> Signup and view all the answers

    Which of the following is a primary effect of aspirin's inhibition of COX-2?

    <p>Decreased prostaglandin production</p> Signup and view all the answers

    What is the primary reason for aspirin's antithrombotic effect to persist even after the drug is discontinued?

    <p>Aspirin delays the release of thromboxane A2 from platelets</p> Signup and view all the answers

    Why is it recommended to discontinue aspirin at least 5 days prior to surgery?

    <p>To avoid excessive bleeding due to prolonged platelet inhibition</p> Signup and view all the answers

    Which enzyme is gets irreversible acetylation by aspirin?

    <p>COX-1</p> Signup and view all the answers

    Why can other NSAIDs be discontinued immediately before surgery, unlike aspirin?

    <p>They do not affect platelet function</p> Signup and view all the answers

    Which of the following is the role of the flanking sequences adjacent to the target region in PCR?

    <p>They serve as primers to start DNA replication.</p> Signup and view all the answers

    Which step of PCR involves thermal separation of the DNA template into single strands?

    <p>Denaturing</p> Signup and view all the answers

    What is the purpose of the annealing step in PCR?

    <p>To combine primers with the denatured, single-stranded flanking ends</p> Signup and view all the answers

    Which enzyme is responsible for forming new daughter DNA strands in the 5' to 3' direction during the elongation step of PCR?

    <p>DNA polymerase</p> Signup and view all the answers

    What is the primary goal of PCR?

    <p>To amplify specific DNA segments, even without knowing their exact sequence</p> Signup and view all the answers

    Which technique is commonly used to separate DNA fragments based on size?

    <p>E) Gel electrophoresis</p> Signup and view all the answers

    Which enzyme is responsible for the subsequent catabolism of 2,3-BPG to 3-phosphoglycerate in erythrocytes?

    <p>Bisphosphoglycerate phosphatase</p> Signup and view all the answers

    What effect does higher 2,3-BPG levels have on oxygen delivery to the tissues by hemoglobin?

    <p>It increases oxygen delivery to the tissues</p> Signup and view all the answers

    How does the conversion of 1,3-BPG to 2,3-BPG affect the net ATP gain in erythrocytes?

    <p>It decreases net ATP production</p> Signup and view all the answers

    What is the primary function of von Willebrand factor (vWF) in hemostasis?

    <p>It stabilizes factor VIII in the blood</p> Signup and view all the answers

    Which enzyme is primarily inhibited by aspirin when administered in low doses, resulting in a sustained decrease in thromboxane A2 production and subsequent antithrombotic effects?

    <p>Cyclooxygenase-1 (COX-1)</p> Signup and view all the answers

    Which of the following is the likely consequence of a β-globin mutation that decreases the positive charge of the 2,3-BPG binding pocket in hemoglobin?

    <p>Increased affinity of hemoglobin for oxygen</p> Signup and view all the answers

    What is the primary function of 2,3-BPG in relation to hemoglobin?

    <p>Decrease oxygen-hemoglobin affinity</p> Signup and view all the answers

    How does fetal hemoglobin (HbF) differ from adult hemoglobin A in terms of its binding affinity to 2,3-BPG?

    <p>HbF does not bind to 2,3-BPG as well as HbA.</p> Signup and view all the answers

    What is the role of the γ chains in fetal hemoglobin (HbF) in terms of 2,3-BPG binding?

    <p>They increase HbF's oxygen affinity.</p> Signup and view all the answers

    Question 7: What effect does a decrease in positive charge within the 2,3-BPG binding pocket of hemoglobin have on its interaction with 2,3-BPG?

    <p>It weakens the interaction.</p> Signup and view all the answers

    Question 8: Which type of mutation in the β-globin chain leads to the formation of hemoglobin C?

    <p>Replacement of a glutamate by lysine</p> Signup and view all the answers

    Question 9: How does hemoglobin C affect the affinity of hemoglobin for oxygen and 2,3-BPG?

    <p>It has no effect on affinity for oxygen or 2,3-BPG.</p> Signup and view all the answers

    Question 10: What characteristic of fetal hemoglobin (HbF) is responsible for its higher oxygen affinity compared to adult hemoglobin A?

    <p>Replacement of histidine with serine in γ chains leading to reduction of the positive charge pocket in the hemoglobin protein.</p> Signup and view all the answers

    Question 11: What effect does a decrease in positive charge within the 2,3-BPG binding pocket of hemoglobin have on its interaction with 2,3-BPG?

    <p>It weakens the interaction.</p> Signup and view all the answers

    Question 8: What is the primary role of ADAMTS13 deficiency in the development of thrombotic thrombocytopenic purpura (TTP)?

    <p>Promoting platelet aggregation</p> Signup and view all the answers

    Question 9: Which statement accurately describes the diagnostic criteria of TTP?

    <p>Thrombocytopenia and microangiopathic hemolytic anemia are essential for diagnosis.</p> Signup and view all the answers

    Which epidermal growth factor receptor is commonly overexpressed by aggressive breast cancers and targeted by monoclonal antibodies like trastuzumab?

    <p>HER2</p> Signup and view all the answers

    What is the primary mechanism of tumor regression seen with monoclonal antibody treatment targeting HER2 in breast cancer?

    <p>Antibody-dependent cellular cytotoxicity (ADCC)</p> Signup and view all the answers

    Which step of ADCC involves the release of granules containing perforin and granzymes by natural killer (NK) cells?

    <p>NK cell binding to target cell Fc portion</p> Signup and view all the answers

    What is the role of CD16 in antibody-dependent cellular cytotoxicity (ADCC)?

    <p>It facilitates NK cell attachment to antibody-bound cells</p> Signup and view all the answers

    What is the primary reason natural killer (NK) cells are considered part of the innate immune system?

    <p>They do not interact with MHC complexes to differentiate self from nonself</p> Signup and view all the answers

    What distinguishes natural killer (NK) cells from cytotoxic T-cells in their recognition of tumor cells?

    <p>NK cells target tumor cells expressing MHC class I</p> Signup and view all the answers

    Which one of these is the most correct about hemoglobin and myoglobin?

    <p>Myoglobin has a higher affinity for oxygen than hemoglobin</p> Signup and view all the answers

    Which enzyme is responsible for forming new daughter DNA strands in the 5' to 3' direction during the elongation step of PCR?

    <p>DNA polymerase III</p> Signup and view all the answers

    What is the main product of COX-2 enzyme activity, which is inducibly expressed and contributes to fever, inflammation, and pain sensitivity?

    <p>Prostaglandin E2</p> Signup and view all the answers

    Question 1: In which cellular organelles does the first and the final 3 steps of heme synthesis occur?

    <p>Mitochondria</p> Signup and view all the answers

    Question 2: What is the primary site of heme synthesis in the body?

    <p>Bone marrow</p> Signup and view all the answers

    Question 3: What is the lifespan of mature red blood cells (erythrocytes) in circulation?

    <p>120 days</p> Signup and view all the answers

    Question 4: Which type of cells principally synthesize heme in the bone marrow?

    <p>Erythrocyte precursor cells</p> Signup and view all the answers

    Question 5: What is the fate of erythrocyte precursor cells as they mature into mature red blood cells?

    <p>They lose their nuclei and mitochondria</p> Signup and view all the answers

    Question 6: What is the significance of erythrocytes losing their mitochondria during maturation?

    <p>They lose the ability to generate heme and hemoglobin</p> Signup and view all the answers

    Question 7: Which cellular organelles typically disappear during erythrocyte development?

    <p>Nucleus</p> Signup and view all the answers

    Question 10: What is the primary reason for impaired generation of new blood cells in response to acute stressors such as blood loss or hypoxia in older individuals?

    <p>Decreased hematopoietic stem cell function</p> Signup and view all the answers

    Study Notes

    von Willebrand Factor (vWF) and Hemostasis

    • vWF mediates platelet adhesion to subendothelial collagen after endothelial damage.
    • The ristocetin cofactor assay measures vWF-dependent platelet agglutination to diagnose vWF deficiency.
    • In vWF deficiency, patients have impaired platelet agglutination in the presence of ristocetin.
    • Ristocetin activates vWF to bind platelets to collagen, allowing for assessment of vWF activity.
    • vWF also stabilizes factor VIII, preventing its degradation in circulation.

    Platelet Disorders and Effects

    • Bernard-Soulier syndrome is characterized by thrombocytopenia, enlarged platelets, and impaired adhesion due to glycoprotein Ib receptor deficiency.
    • Glanzmann thrombasthenia shows normal ristocetin-induced agglutination but has deficient platelet aggregation due to glycoprotein IIb/IIIa receptor deficiency.
    • Patients with Glanzmann thrombasthenia have mucocutaneous bleeding and show no response to ristocetin.

    Aging and Hematopoiesis

    • Impaired generation of blood cells in older individuals is due to decreased bone marrow response to stimulatory cytokines.
    • Older patients exhibit increased bone marrow fat, limiting hematopoiesis.
    • The significance of increased medullary cavity size relates to age-related changes that affect blood cell production.
    • Hematopoietic stem cell destruction leads to fat replacement of the bone marrow.

    Cytokines and Inflammatory Responses

    • Thrombopoietin production is stimulated by cytokines in response to infections.
    • Reactive thrombocytosis arises from elevated thrombopoietin levels during inflammatory processes.
    • Hepcidin release during inflammation restricts iron availability, leading to anemia characterized by reduced iron accessible for reticulocytosis.

    Megaloblastic Anemia and Nutritional Deficiencies

    • Symptoms of megaloblastic anemia include exertional dyspnea, fatigue, and hypersegmented neutrophils.
    • Folate and vitamin B12 deficiencies impair DNA synthesis, causing slowed nuclear division compared to cytoplasmic maturation.
    • Vitamin B12 deficiency is linked to complications such as neurologic issues, unlike folate deficiency.
    • Megaloblastic anemia causes typical findings, such as macrocytic red cells on peripheral blood smear.

    Hemoglobin and Oxygen Binding

    • Adult hemoglobin primarily exists as hemoglobin A (HbA), responsible for oxygen transport in the blood.
    • 2,3-BPG binds hemoglobin, influencing oxygen delivery to tissues and shifting the dissociation curve to the right, facilitating oxygen release.
    • Fetal hemoglobin (HbF) has a lower affinity for 2,3-BPG, enhancing oxygen binding compared to adult hemoglobin.
    • β-Globin mutations can alter hemoglobin's affinity for oxygen and 2,3-BPG, influencing oxygen transport.

    Aspirin's Mechanism of Action

    • Aspirin irreversibly inhibits cyclooxygenase-1 (COX-1), reducing thromboxane A2 production, an essential factor for platelet aggregation.
    • The prolonged antithrombotic effect of aspirin persists due to irreversible modification of COX-1.
    • Aspirin should be discontinued before surgery to reduce bleeding risk, unlike other NSAIDs that can be stopped immediately.

    PCR and DNA Synthesis

    • PCR involves amplifying specific DNA sequences using thermal cycling, including denaturation, annealing, and elongation.
    • DNA polymerase synthesizes new DNA strands during the elongation phase of PCR.
    • Gel electrophoresis separates DNA fragments based on size, enabling analysis of PCR products.

    General Hematopoietic Insights

    • The lifespan of mature erythrocytes is approximately 120 days in circulation, undergoing maturation from erythrocyte precursors in the bone marrow.
    • Erythrocytes lose mitochondria and organelles during maturation, optimizing them for oxygen transport.
    • Synthesis of heme primarily occurs in the bone marrow, with deficiencies impacting overall hematopoiesis and oxygen transport capacity.

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    Test your knowledge of von Willebrand factor (vWF) and platelet disorders with this quiz. Explore the role of vWF in hemostasis, laboratory tests for vWF deficiency, and different platelet disorders such as Glanzmann thrombasthenia and Bernard-Soulier syndrome.

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