17. The Blood

What is the difference between prothrombin and thrombin?

Define fibrinolysis

What is the importance of this process?

What contribution from the intrinsic and the extrinsic pathways is necessary for the common pathway to begin?

How is clot overgrowth usually prevented?

List two conditions that may lead to unnecessary (and undesirable) clot formation.

Define hemostasis

List the three major phases of coagulation. Explain what initiates each phase and what the phase accomplishes

In what general way do the intrinsic and extrinsic mechanisms of clotting differ?

Which ion is essential to virtually all stages of coagulation?

Why is aspirin sometimes prescribed for the prevention of vascular problems?

A test for prothrombin time is used to identify deficiencies in the extrinsic clotting pathway; prothrombin time is prolonged if any of the factors are deficient. A test for activated partial thromboplastin time is used in a similar fashion to detect deficiencies in the intrinsic clotting pathway. Which factor would be deficient if a person had a prolonged prothrombin time but a normal partial thromboplastin time?

Almost half of our vitamin K is synthesized by bacteria that inhabit the large intestine. Based on this information, how could taking a broad-spectrum antibiotic for a long time cause frequent nosebleeds?

Number the steps of hemostasis in order, putting 1 by the first event, 2 by the second, and so on. 

____The intrinsic/contact activation and extrinsic/tissue factor pathways produce factor Xa. 

____The clot retracts. 

____Thrombin converts fibrinogen to fibrin, and fibrin glues the plug together. 

____Platelets are activated, and the platelet plug forms. 

____Vasoconstriction and increased tissue pressure decrease blood flow through the vessel. 

____Tissue plasminogen activator activates plasmin, which degrades fibrin. 

____The common pathway produces thrombin.

How do the intrinsic/contact activation and extrinsic/tissue factor coagulation pathways differ? How are they similar?

What are the overall goals of the common pathway of coagulation?

Which of the following is not an anticlotting agent produced by endothelial cells?

a. Prostacyclin

b. Protein C

c. Antithrombin-III

d. Warfarin

Tissue plasminogen activator, urokinase, and plasmin are important components of:

a. Coagulation

b. Fibrinolysis

c. Platelet plug formation

d. Hemostasis

The anticoagulant drug warfarin primarily disrupts the extrinsic/tissue factor coagulation pathway. Explain why disrupting only this pathway disrupts the entire coagulation cascade.

Cirrhosis of the liver often reduces production of many types of plasma proteins, including albumin and clotting factors. Predict the effects on the body of decreased numbers of these proteins in the plasma. Would this also affect the number of γ-globulins in the plasma? Why or why not?