Haemostasis

Question 1

What does the endothelium produce?

Answer 1

• Heparins
• TFPI
• Thrombomodulin
• Prostacyclin
• Nitric oxide

Question 2

What is the key job of the endothelium?

Answer 2

• Prevent cells sticking to the walls

- Encourage flow

Question 3

What happens when you cut yourself?

Answer 3

• You bleed at the site of injury
• It stops and a clot forms
• The clot remains confined to the site of injury
• 1 week later the clot has vanished

Question 4

What is clotting dependent on?

Answer 4

• Platelets
• vWF factor
• Coagulation factors

Question 5

Why does the clot remain confined to the site of injury?

Answer 5

So that the whole system does not become occluded. This is done by anti-coagulants

Question 6

How is the clotting system activated?

Answer 6

• Resting platelets and coagulation factors are activated by signals and localised to the area of damage
• These signals include abnormal wall surface and physiological activators
• Vessel damage leads to platelet adhesion

Question 7

What receptors are present on the surface of platelets?

Answer 7

• ADP receptor
• Epinephrine receptor
• Thrombin receptor

Question 8

What glycoproteins are present on the surface of platelets?

Answer 8

• GP IIb/IIIa
• GP Ib/V/IX
• GP Ia/IIa
• GP VI

Question 9

What granules are present in platelets?

Answer 9

• Alpha granule

- Dense granule

Question 10

What do the glycoprotein receptor on the surface of platelets binds to?

Answer 10

Some bind to

• Collagen and the vessel wall
• von Willbrand factor
• Fibrinogen

Question 11

What role do platelets play in haemostasis?

Answer 11

• Adhere to area of damage
• Activate EDP pathway and cylo-oxygenase pathway
• Aggregate
• Provide a phospholipid surface for coagulation
• Form a plug with fibrinogen in primary haemostasis

Question 12

What forms the primary haemostatic clot?

Answer 12

Platelets

Question 13

What forms the definitive haemostatic clot?

Answer 13

Fibrin

Question 14

What is the clotting factor cascade which activates clot formation?

Answer 14

• Factor XII
• Factor XI
• Factor IX
• Factor VIII
• Factor X
• Prothrombin
• Fibrinogen

Question 15

What prevents the clotting cascade?

Answer 15

Anticoagulants

Question 16

Where is the defect in haemophilia A?

Answer 16

Factor IX is deficient

Question 17

Where is the defect in haemophilia B?

Answer 17

Factor VIII is deficient

Question 18

How is tissue factor produced?

Answer 18

Produced by damaged tissues

Question 19

Give examples of natural anticoagulants and what they target.

Answer 19

Tissue factor pathway inhibitor
-Bind to an inactivates the activated factor X and VII

Protein C and S
-Target activated factor V and VIII

Antithrombin
-Inhibits activated factor X and thrombin

Question 20

What is fibrinolysis?

Answer 20

Process in which clots are broken down

Question 21

How does fibrinolysis occur?

Answer 21

• Endothelium produces activators of plasminogen: t-PA and u-PA
• Plasminogen is cleaved to active plasmin
• Plasmin breaks the clot down resulting in fibrin degradation products including D-dimer

Question 22

What ensures there is not too much fibrinolysis?

Answer 22

Inhibitors of plasminogen and plasmin

Question 23

What is the mechanism of aspirin?

Answer 23

Inhibits COX which inhibits arachidonic acid and thromboxane

Question 24

What is the mechanism of clopidogrela and ticagrelor?

Answer 24

Acts on the EDP pathway

Question 25

What is the mechanism of warfarin?

Answer 25

• Reduces the amount of coagulation factors 2,7,9 and 10 (vitamin K dependent).
• It inhibits vitamin K

Question 26

What is the mechanism of riveroxaban?

Answer 26

Target factor X and inactivate it

Question 27

What is the mechanism of dibigatran?

Answer 27

Oral inhibitor of thrombin

Question 28

What is the mechanism of abciximab?

Answer 28

Prevents glycoproteins IIb/III binding to fibrinogen