Haemostasis

Question 1

In terms of coagulation cascade: in the body what is more significant, the intrinsic or extrinsic pathway?

Answer 1

Extrinsic, the intrinsic is almost irrelevant

Question 2

How is the extrinsic pathway activated?

Answer 2

By an injury - this leads to activation of TF

Question 3

From activation of tissue factor to formation of thrombin

Answer 3

TF acts on VII > VIIa
VIIa acts on X > Xa
Xa (with Va) acts on prothrombin > thrombin

Question 4

How many factors are directly involved in the formation of Xa (which leads to formation of thrombin) (3)

Answer 4

VIIa

VIIIa & IXa work together to cleave X

Question 5

What factors result in direct activation of thrombin? (2)

Answer 5

Va & Xa

Question 6

Once prothrombin is activated into thrombin, a thrombin burst occurs - which factors does thrombin stimulate to achieve this? (3) At the same time it activates its inhibitor - what is it called?

Answer 6

V > Va (acts to form more thrombin with Xa)
VIII > VIIIa (acts with IXa to from Xa)
XI > XIa …which results in more IXa
Thrombomodulin

Question 7

Actions of protein C (2)

Answer 7

Inhibits Va formation

Inhibits VIIIa formation

Question 8

APTT is a measure of which pathway? And which drug therapy is usually monitored

Answer 8

Intrinsic pathway

Heparin

Question 9

PT is a measure of which pathway? and which drug therapy is usually monitored?

Answer 9

Extrinsic

Warfarin

Question 10

Warfarin MOA? which factors inhibited? (4)

Answer 10

Inhibits Vit K dependent factors
27, 9 & 10; buses that run on high street ken: II, VII, Ix, X
Also Protein C, S & Z