Justina haemostasis tut

Question 1

What is thrombosis?

Answer 1

blood clot within an intact blood vessel

usually happens in veins since lower bp

Question 2

What is Virchow’s triad?

Answer 2

3 factors contributing to thrombosis

1) blood - dominant in venous thrombosis
2) vessel wall - dominant in arterial thrombosis
3) blood flow - complex contributes to both

Question 3

What are the characteristics of platelets?

Answer 3

discoid shape
no nucleus
contains granules

Question 4

What does platelet adhesion do?

Answer 4

activates platelets to change shape from disc rounded w spicules

Question 5

What is indirect platelet adhesion?

Answer 5

platelet GlpIb receptor binds to von Willebrand factor

Question 6

What is direct platelet adhesion?

Answer 6

platelet GlpIa receptor binds directly

Question 7

What is the advantage of having spicules?

Answer 7

to encourage platelet-platelet interaction

Question 8

What enzyme catalyses the formation of thromboxane A2?

Answer 8

cyclo-oxygenase COX1/2

Question 9

Where is prostacyclin PG12 released from?

Answer 9

endothelial cells

Question 10

What does PG12 do?

Answer 10

vasodilator
suppressed platelet activation
inhibits platelet aggregation

Question 11

What are 2 antiplatelet drugs?

Answer 11

aspirin
clopidogrel

Question 12

How does aspirin work?

Answer 12

irreversibly blocks COX
inhibits thromboxane A2 production
irreversibly inhibits platelet activation and aggregation

Question 13

How does clopidogrel work?

Answer 13

irreversibly blocks ADP receptor P2Y12 on platelet membrane

Question 14

Why is prostacyclin still produced despite the fact that aspirin blocks COX?

Answer 14

COX is an enzyme which requires a nucleus to be produced
platelets have no nucleus unlike endothelial cells
prostacyclin is released by endothelial cells which can make MORE COX

Question 15

What factors require vit K to be functional?

Answer 15

Factors II, VII, XI, X

use 1972 to remember

Question 16

What occurs during initiation phase?

Answer 16

triggered by TF

1) TF binds to factor 7a
2) Factor 9 -> 9a, factor 10 -> 10a
3) Factor 2 (PROTHROMBIN) -> small initial amount of 2a (THROMBIN)

Question 17

What occurs during amplification phase?

Answer 17

small amount of thrombin activates

1) co-factors 5 and 8 -> 5a and 8a
2) zymogen factor 11 -> 11a
3) platelets

Question 18

What occurs during propagation phase?

Answer 18

1) Factor 11a activates factor 9 -> 9a
2) Factors 9a and 8a AMPLIFIES factor 10 -> 10a -> rapid burst of thrombin generation
3) thrombin CLEAVES FIBRINOGEN to form insoluble fibrin clot

Question 19

What are the inhibitory mechanisms of the natural anticoagulant pathways?

Answer 19

protein C
protein S
antithrombin

Question 20

Why do anticoagulant drugs require longer chains of heparin to inactivate thrombin?

Answer 20

heparin has to wrap around BOTH antithrombin and thrombin
-> indirectly inhibits thrombin

Question 21

Why does it take several days for warfarin to take effect?

Answer 21

reduces synthesis of coagulation factors rather than inhibiting existing factors