1. How do platelets participate in the body’s defense mechanism?

A. They produce antibodies B. They agglutinate to encircle and destroy foreign bodies C. They release complement proteins D. They promote swelling and inflammation

2. Congenital absence of which protein is linked to fatal thrombosis in infancy?

A. Protein S B. Protein C C. Factor VIII D. Thrombomodulin

3. Von Willebrand disease leads to excessive bleeding because:

A. Platelet count is abnormally low B. There is deficiency of a protein aiding platelet adhesion and maintenance of factor VIII C. There is excessive production of thrombin D. Platelets cannot contract to retract the clot

4. What is ischemia and how does it affect tissue?

A. Excess bleeding causing tissue swelling B. Insufficient blood supply causing hypoxia and potential tissue damage C. Overproduction of platelets leading to thrombosis D. Inflammation resulting in increased blood flow

5. Idiopathic thrombocytopenic purpura is believed to result from:

A. Viral infection B. Development of antibodies against platelets C. Deficiency of calcium D. Overactivation of clotting cascade

6. What is thrombosis?

A. The formation of blood cells B. Coagulation of blood inside blood vessels C. The destruction of blood clots D. Formation of fibrinolysin

7. What is the mechanism of anticoagulants like EDTA and oxalate compounds?

A. Enhance fibrinogen activity B. Remove calcium from blood preventing coagulation C. Activate platelets D. Destroy thrombin

8. Why does congenital absence of protein C lead to thrombosis?

A. Protein C activates platelets B. Protein C inhibits the formation of fibrin C. Protein C inactivates factors V and VIII; without it, clotting factors remain active causing clot formation D. Protein C breaks down thrombin directly

9. What substance stabilizes loose fibrin strands into a dense mesh?

A. Factor XIII (Fibrin-stabilizing factor) B. Factor VIII C. Plasmin D. Platelet phospholipids

10. How does fibrinolysis occur in blood vessels?

A. Activation of thrombin only B. Activation of plasmin from plasminogen by tissue plasminogen activator (t-PA) and other enzymes C. Increased platelet aggregation D. Inactivation of antithrombin III

11. What is the effect of thrombomodulin-thrombin complex formation on clotting?

A. Enhances fibrin formation B. Activates protein C to reduce clotting C. Activates platelets immediately D. Directly converts prothrombin to thrombin

12. What is the role of calcium ions (Factor IV) in blood coagulation?

A. They inactivate thrombin after clot formation B. They assist in the conversion of prothrombin into thrombin and activate several clotting factors C. They dissolve the fibrin meshwork D. They inhibit platelet activation

13. What is the difference between necrosis and infarction?

A. Necrosis is localized tissue death, infarction is generalized inflammation B. Necrosis is tissue death from any cause; infarction is tissue death specifically due to loss of blood supply C. Infarction refers to tissue swelling; necrosis refers to tissue repair D. They are synonymous terms

14. Which contractile proteins found in platelets are responsible for clot retraction?

A. Actin, myosin, and thrombosthenin B. Hemoglobin, fibrin, and collagen C. Thromboplastin, prothrombin, and fibrinogen D. Antithrombin, plasmin, and kallikrein

15. How do platelets contribute to the prevention of blood loss after vessel injury?

A. By secreting hemoglobin B. By forming a temporary plug and causing vasoconstriction C. By activating factor VII only D. By producing antibodies

16. What is an embolism?

A. Clotting of blood outside vessels B. Detachment and movement of thrombus blocking small vessels C. Formation of platelet plug D. Natural breakdown of blood clots

17. How do platelets contribute to clot retraction?

A. By releasing tissue thromboplastin B. Through contractile proteins like actin, myosin, and thrombosthenin in their cytoplasm C. By secreting serotonin to constrict blood vessels D. By producing plasminogen activators

18. Which substance produced by platelets aids in the repair of ruptured blood vessels?

A. Heparin B. Platelet-derived growth factor (PDGF) C. Von Willebrand factor D. Thrombomodulin

19. Which of the following best describes purpura?

A. Prolonged clotting time with normal bleeding time B. Prolonged bleeding time with normal clotting time and spontaneous subcutaneous bleeding C. Excessive clotting in capillaries D. Deficiency of prothrombin activator

20. Which of the following best explains how platelets contribute to hemostasis during blood vessel injury?

A. Platelets release tissue thromboplastin to activate the extrinsic clotting pathway B. Platelets provide a surface for fibrinogen to directly convert into fibrin threads C. Platelets secrete serotonin to constrict blood vessels, adhere to damaged sites, and form a temporary plug D. Platelets produce plasmin to dissolve blood clots after they form

21. Which of the following is NOT a mechanism by which platelets help prevent blood loss?

A. Secretion of 5-HT causing blood vessel constriction B. Adhesion to seal vessel damage C. Formation of a temporary plug at injury site D. Activation of fibrinolysis to dissolve clots

22. What differentiates necrosis from infarction?

A. Necrosis is tissue death due to all causes; infarction is tissue death due specifically to loss of blood supply B. Necrosis involves blood clots; infarction involves infections C. Infarction is reversible; necrosis is not D. Necrosis only affects skin; infarction affects internal organs

23. What is the function of platelet-derived growth factor (PDGF)?

A. It breaks down clots B. It repairs ruptured blood vessels and restores endothelium C. It activates platelets during clot formation D. It inhibits thrombin activity

24. Which organs are most commonly affected by embolism?

A. Liver, pancreas, and intestines B. Lungs, brain, and heart C. Bones, skin, and muscles D. Spleen, thymus, and lymph nodes

25. What role does sodium or calcium alginate play in blood coagulation?

A. Activate Hageman factor to enhance clotting B. Remove calcium from blood C. Inactivate platelets D. Break down fibrin

26. What is the mechanism by which heparin prevents blood clotting?

A. It directly inactivates fibrinogen B. It combines with antithrombin III to inactivate thrombin and other clotting factors C. It removes calcium ions from blood plasma D. It activates platelet aggregation

27. What happens when blood flow is sluggish?

A. Platelets decrease in number B. Clotting factors are deactivated C. Platelets aggregate leading to thrombus formation D. Blood becomes less viscous

28. Which blood coagulation factor is activated in both intrinsic and extrinsic pathways to form prothrombin activator?

A. Factor VII B. Factor X C. Factor VIII D. Factor XII

29. Embolism refers to:

A. Formation of a blood clot within a vessel B. Formation of new blood vessels after injury C. Detachment and movement of a thrombus through the bloodstream causing vessel occlusion D. Tissue death due to lack of blood supply

30. What is the positive feedback effect of thrombin during clotting?

A. Thrombin inhibits platelet aggregation B. Thrombin activates factor V to accelerate prothrombin activator formation C. Thrombin inactivates factor VIII D. Thrombin prevents fibrinogen conversion

31. In purpura, bleeding time is prolonged due to:

A. Deficiency of clotting factors B. Deficiency or dysfunction of platelets while clotting time remains normal C. Excess production of anticoagulants D. Deficiency of von Willebrand factor

32. What is the role of activated protein C in anticoagulation?

A. Activates platelets B. Inactivates clotting factors V and VIII in presence of protein S C. Converts fibrinogen into fibrin D. Activates thrombin

33. What is the primary role of platelets in blood clotting?

A. Formation of prothrombin activator B. Production of red blood cells C. Secretion of hemoglobin D. Destruction of white blood cells

34. How is warfarin effective as an oral anticoagulant?

A. Activates vitamin K B. Inhibits vitamin K action, affecting factors II, VII, IX, and X C. Binds and neutralizes thrombin D. Increases platelet aggregation

35. Which of the following is an anticoagulant naturally produced by the body?

A. Prothrombin B. Heparin C. Fibrinogen D. Thromboplastin

36. Which substance is used to store blood in blood banks due to its anticoagulant property?

A. Thrombin B. Acid citrate dextrose (ACD) C. Calcium alginate D. Thromboplastin

37. Which factor plays a central role in converting prothrombin into thrombin?

A. Factor IV (Calcium) B. Prothrombin activator complex (including activated factor X and V) C. Factor XIII D. Thrombomodulin

38. In the extrinsic pathway, the initiation for clotting starts by:

A. Platelet activation B. Release of tissue thromboplastin (factor III) from damaged tissues C. Activation of factor XII D. Interaction with collagen fibers

39. What is the function of thrombomodulin in the anticoagulation process?

A. Activates thrombin to promote clotting B. Binds thrombin and forms a complex that activates protein C, leading to inactivation of factors V and VIII C. Activates platelets at the site of injury D. Converts fibrinogen to fibrin

40. What role does heparin play in anticoagulation?

A. Directly activates thrombin B. Inhibits thrombin and activates antithrombin III C. Removes calcium from blood D. Forms calcium citrate

41. Which factor is responsible for stabilizing fibrin threads into a dense meshwork during clot formation?

A. Factor V B. Factor XIII (Fibrin-stabilizing factor) C. Factor VIII D. Factor XII

42. How does warfarin exert its anticoagulant effect?

A. By directly inhibiting thrombin activity B. By removing calcium from blood C. By inhibiting vitamin K, essential for the formation of factors II, VII, IX and X D. By activating antithrombin III

43. Which process describes the conversion of fibrinogen into fibrin?

A. Fibrinolysis B. Clot retraction C. Polymerization of fibrin monomers stabilized by factor XIII D. Platelet degranulation

44. Which of the following is NOT a cause of thrombosis?

A. Injury to blood vessels B. Smooth endothelial lining C. Sluggish blood flow D. Agglutination of RBCs

45. What distinguishes thrombasthenic purpura?

A. Low platelet count B. Structural or functional platelet abnormality with normal platelet count C. Excessive platelet production D. Deficiency of factor VIII

46. What condition defines ischemia?

A. Excess bleeding after injury B. Insufficient blood supply to an organ leading to hypoxia C. Excess clotting causing vessel rupture D. Infection of blood vessels

47. Thrombocytopenic purpura is caused by:

A. Deficiency of clotting factors B. Deficiency of platelets C. Overproduction of platelets D. Deficiency of von Willebrand factor

48. What is the effect of cold temperature on blood clotting?

A. Accelerate coagulation B. Postpone coagulation by lowering temperature to about 5°C C. No effect D. Disintegrate formed clots

49. Von Willebrand disease leads to excessive bleeding primarily because of:

A. Deficiency of fibrinogen B. Deficiency of von Willebrand factor affecting platelet adhesion and factor VIII stability C. Excess platelet adhesion D. Over-activation of thrombin

50. Which of the following is NOT involved in the intrinsic pathway of prothrombin activator formation?

A. Factor XII activation by contact with collagen B. Factor III (tissue thromboplastin) release from injured tissues C. Activation of factor IX by factor XIa D. Platelet phospholipid involvement