Haemostasis

Question 1

What is haemostasis?

Answer 1

The arrest of bleeding and the maintenance of vascular patency

Question 2

What are 4 requirements of haemostasis?

Answer 2

Permanent state of readiness
Prompt response
Localised response
Protection against unwanted thrombosis

Question 3

What are the 4 components of a normal haemostatic system?

Answer 3

1. Formation of platelet plug
2. Formation of fibrin clot
3. Fibrinolysis
4. Anticoagulant defences

Question 4

How are platelets formed in the bone marrow?

Answer 4

By ‘budding’ from megakaryocytes

Question 5

How long is the average platelets lifespan?

Answer 5

7-10 days

Question 6

What is released as a result of exposed collagen due to endothelial damage?

Answer 6

Von Willebrand factor

Question 7

What occurs by platelets at the site of injury?

Answer 7

Adhesion

Question 8

Name some consequences of failure of platelet plug formation?

Answer 8

Spontaneous bruising and purpura
Mucosal bleeding
Intracranial haemorrhage
Retinal haemorrhages

Question 9

Name 3 reasons for the failure of fibrin clot formation?

Answer 9

Single clotting factor deficiency
Multiple clotting factor deficiencies
Increased fibrinolysis

Question 10

Name 3 reasons for failure of platelet plug formation?

Answer 10

Vascular reasons
Platelets - reduced number/function
Von Willebrand factor failure

Question 11

What converts prothrombin to thrombin?

Answer 11

Clotting factors V and Xa

Question 12

What does tissue factor (TF) do?

What is this called?

Answer 12

Activate clotting factor VIIa

Initiation

Question 13

What two actions does thrombin have?

Answer 13

It converts fibrinogen to fibrin and activates clotting factors VIII and IXa

Question 14

What does clotting factors XIII and IX do?

Answer 14

Activate clotting factors V and Xa

Question 15

What does clotting factors V and Xa do?

Answer 15

Convert prothrombin to thrombin

Question 16

What are the three stages in the formation of a fibrin clot?

Answer 16

Initiation
Propagation
Amplification

Question 17

What occurs in fibrinolysis?

Answer 17

Fibrin is broken down into FDPs (fibrin degradation products)

Question 18

What causes the breakdown of fibrin to FDPs?

Answer 18

Plasmin

Question 19

How is plasmin formed?

Answer 19

Plasminogen is converted to plasmin by tPA (tissue plasminogen activator)

Question 20

What are the most common site(s) of bleed in haemophilia patients?

Answer 20

Lower limb (hinge) joints - ankles and knees
Elbows can also be affected

Question 21

What two screening tests are use in fibrin clot formation investigation?

Answer 21

Prothrombin time (PT)
Activated partial thromboplastin time (aPTT)

Question 22

What is added to a patient in prothrombin time investigations?

Answer 22

Phospholipid
Tissue factor
Calcium

Question 23

What does prothrombin time depend on?

Answer 23

The amount / efficiency of clotting factor VIIa

Question 24

What is the extrinsic fibrin clot formation pathway?

Answer 24

Tissue factor pathway (prothrombin time)

Question 25

What is the intrinsic fibrin clot formation pathway?

Answer 25

The factor VIII / IXa pathway (activated partial thromboplastin time)

Question 26

Name three types of naturally occurring anticoagulants?

Answer 26

Serine protease inhibitors (anti-thrombin) Protein C and protein S

Question 27

What is 'primary haemostasis'?

Answer 27

Formation of a platelet plug

Question 28

What is 'secondary haemostasis'?

Answer 28

Formation of a fibrin clot

Question 29

What is involved in platelet plug formation?

Answer 29

Platelets and Von Willebrand factor

Question 30

What does thrombin activate to cause a positive feedback loop?

Answer 30

Clotting factor IXa

Question 31

Where are coagulation factors synthesised?

Answer 31

In hepatocytes

Question 32

What can cause a reduced production of coagulation factors?

Answer 32

Liver failure