Coagulation

Question 1

Factor XII has no role in physiologic coagulation. Why does it not cause bleeeding?

Answer 1

Factor XII is one of the contact factors, and thus its role in initiating coagulation occurs when the blood is exposed to foreign substances such as extracorporeal circuits or central venous catheters.

In the absence of foreign surfaces, coagulation starts in the subendothelium with activation of tissue factor, which then activates factor VII to factor VIIa, which then activates factor IX and factor X, leading to thrombin generation,

Factor XII does not bind to platelets, but this is not why it does not cause bleeding.

Question 2

prime initiators of physiologic coagulation

Answer 2

Tissue factor and factor VII are the prime initiators of physiologic coagulation.

In the absence of foreign surfaces, coagulation starts in the subendothelium with activation of tissue factor, which then activates factor VII to factor VIIa, which then activates factor IX and factor X, leading to thrombin generation,

Question 3

Primary homeostasis

Answer 3

Collagen, von Willebrand factor, and platelets

Question 4

factors only made in the liver

Answer 4

Fibrinogen and factors VII and II are exclusively made in the liver,

Question 5

You are asked to consult on a newborn girl with purpura fulminans. Upon taking the medical history, you learn that this child had a male sibling who died in the neonatal period after presenting with purpura fulminans. She has three other siblings who are healthy and did not have purpura fulminans.

Which physiologic consequence will result from this child’s underlying condition?

a.	Excess von Willebrand factor high-molecular-weight multimers
b.	Decreased fibrinogen
c.	Inability to inactivate factor VIII
d.	Decreased production of plasminogen
e.	Thrombocytopenia

Answer 5

The protein C/S complex is responsible for inactivating factors V and VIII;

answer c