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Chapter 4: Hemostasis, Surgical Bleeding, and Transfusion

Which of the following is NOT one of the four major physiologic events of hemostasis?

A. Fibrinolysis

B. Vasodilatation

C. Platelet plug formation

D. Fibrin production

Answer: B

Hemostasis is a complex process and its function is to limit blood loss from an injured vessel. Four major physiologic events participate in the hemostatic process: vascular constriction, platelet plug formation, fibrin formation, and fibrinolysis. Though each tend to be activated in order, the four processes are interrelated so that there is a continuum and multiple reinforcements. (See Schwartz 10th ed., p. 85.)

Which is required for platelet adherence to injured endothelium?

A. Thromboxane A2

B. Glycoprotein (GP) IIb/IIIa

C. Adenosine diphosphate (ADP)

D. Von Willebrand factor (vWF)

Answer: D

Platelets do not normally adhere to each other or to the vessel wall but can form a plug that aids in cessation of bleeding when vascular disruption occurs. Injury to the intimal layer in the vascular wall exposes subendothelial collagen to which platelets adhere. This process requires von Willebrand factor (vWF), a protein in the subendothelium that is lacking in patients with von Willebrand disease. vWF binds to glycoprotein (GP) I/IX/V on the platelet membrane. Following adhesion, platelets initiate a release reaction that recruits other platelets from the circulating blood to seal the disrupted vessel. Up to this point, this process is known as primary hemostasis. Platelet aggregation is reversible and is not associated with secretion. Additionally, heparin does not interfere with this reaction and thus hemostasis can occur in the heparinized patient. Adenosine diphosphate (ADP) and serotonin are the principal mediators in platelet aggregation. (See Schwartz 10th ed., p. 85.)

Which of the following clotting factors is the first factor common to both intrinsic and extrinsic pathways?

A. Factor I (fibrinogen)

B. Factor IX (Christmas factor)

C. Factor X (Stuart-Prower factor)

D. Factor XI (plasma thromboplasma antecedent)

Answer: C

The intrinsic pathway begins with the activation of factor XII that subsequently activates factors XI, IX, and VII. In this pathway, each of the primary factors is “intrinsic” to the circulating plasma, whereby no surface is required to initiate the process. In the extrinsic pathway, tissue factor (TF) ...

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