Chapter 14 - Alterations In Homeostatsis & Blood Coagulation

Question 1

How do the factors released from platelets contribute to hemostasis?

Answer 1

Factors released from platelets contribute to hemostasis by enhancing vasoconstriction, platelet aggregation, and vessel repair.

Question 2

How is a fibrin clot formation initiated and what is the ultimate result?

Answer 2

By both the intrinsic and extrinsic pathway. Each pathway requires the sequential activation of specific clotting factors, ultimately resulting in enzymatic cleavage of fibrinogen to form an insoluble fibrin clot.

Question 3

When does the initiation of fibrinolysis occur?

Answer 3

Fibrinolysis occurs simultaneously with clot formation to prevent excessive clotting and vessel occlusion.

Question 4

How does one obtain bleeding tendencies?

Answer 4

Bleeding tendencies may be inherited or acquired.

Question 5

What are important risk factors for bleeding tendencies?

Answer 5

Abnormal bleeding, liver disease, and anticoagulant drug use may be important risk factors.

Question 6

What physical findings are indicative of bleeding tendencies?

Answer 6

Petechiae, purpura, ecchymoses, telangiectasia, and occult or frank bleeding are indicative.

Question 7

What are usual laboratory tests included in the evaluation of hemostasis and coagulation?

Answer 7

Platelet count, bleeding time, PT/INR (extrinsic pathway), and activated partial thrombophlebitis time (intrinsic pathway).

Question 8

Disorders of the vasculature that result in altered hemostasis include:

Answer 8

Inflammation (allergic purpura)
Structural abnormalities (collagen diseases)
Weakened vessel walls (telangiectasia)

Question 9

What number indicates an insufficient quantity of platelets?

Answer 9

Fewer than 50,000/mm3

Question 10

What are the important causes of thrombocytopenia?

Answer 10

Autoimmune destruction (ITP)
DIC
Mechanical destruction (artificial valves).

Question 11

What does an insufficient quantity of platelets result from?

Answer 11

Decreased production, sequestration, increased destruction, or dilution.

Question 12

What does an excessive quantity of platelets result from?

Answer 12

Excessive production (proliferation of bone marrow cells).

Question 13

What is considered an excessive quantity of platelets?

Answer 13

More than 400,000/mm3

Question 14

What may thrombocythemia result in?

Answer 14

Excessive coagulation with thrombosis or 
Excessive bleeding (???)

Question 15

A normal platelet count does not ensure adequate platelet function, so what else can cause prolonged bleeding time?

What is the usual cause prolonged bleeding time?

Answer 15

Platelet adhesion, aggregation, and degranulation

The usual cause is drug related (e.g. Aspirin), but rarely, the platelet defect is inherited (e.g. Von Willebrand disease).

Question 16

What can coagulation disorders result from?

Answer 16

Defects in the clotting cascade or fibrinolytic process.

Question 17

Is hemophilia an inherited or acquired bleeding disorder? Which is the most common and which factor is associated with it?

Answer 17

Hemophilia is an inherited disorder that results from deficient clotting production.

Hemophilia A (factor VIII) and hemophilia B (factor IX) are the most common.

Question 18

Is von Willebrand disease inherited or acquired and what clotting factor is associated with it?

Answer 18

Von Willebrand disease is inherited and is caused by abnormal factor VIII carrier protein production. The disease results in a deficiency of factor VIII in the circulation and decreased platelet function.

Question 19

What coagulation disorder is vitamin K deficiency associated with?

Answer 19

Vitamin K deficiency is associated with hemorrhagic disease of the newborn and bleeding related to malnutrition and liver disease.

Question 20

Vitamin K is a necessary cofactor for liver production of which factors?

Answer 20

II
VII
IX
X

Question 21

Is DIC acquired or inherited and how is it caused?

Answer 21

DIC is an acquired bleeding syndrome associated with trauma, malignancy, burns, shock, and abruptio placental.

Question 22

How is DIC characterized?

Answer 22

DIC is characterized by widespread clot formation in small vessels. Clotting factors and platelets are consumed, leaving the patient with deficient resources for the appropriate clot formation. The platelet count and fibrinogen levels are typically decreased, and values for PT, aPTT, thrombin time, bleeding time, and fibrin split products are elevated.

Question 23

What are the critical steps involved in hemostasis?

Answer 23

Vasospasm, formation of a platelet plug, and activation of the clotting cascade to form a fibrin clot