Haemostasis and the Clotting Cascade

Question 1

What is haemostasis?

Answer 1

The process by which haemorrhage is prevented following tissue damage.

Question 2

What are the three steps of haemostasis?

Answer 2

Vascular Spasm
Platelet Plug Formation
Coagulation

Question 3

What is the vascular spasm and what is its purpose in haemostasis?

Answer 3

The contraction of smooth muscle in the blood vessel which constricts the vessel to slow down blood loss and allow platelets better chance of adhesion

Question 4

What causes the vascular spasm?

Answer 4

It is trigger by a neural reflex (initiated by pain receptors) and its effects are maintained/increasing by locally acting chemicals released by activated platelets

Question 5

What are the three stages of platelet plug formation?

Answer 5

Platelet adhesion
Platelet release reaction
Platelet aggregation

Question 6

What do platelets bind to in platelet adhesion?

Answer 6

Exposed collagen and connective tissue of the damaged blood vessel

Question 7

How does the von Willebrand factor (vWf) assist platelet adhesion?

Answer 7

vWf binds to exposed collagen then binds to GPIb on platelets which tethers the platelets to the collagen allowing integrin-alpha2beta1 and GPV1 on the platelet to bind directly to the collagen.

Question 8

What happens during the platelet release reaction?

Answer 8

Platelets release chemicals (thromboxane A2, ADP and serotonin) which increase vasoconstriction and activate passing platelets

Question 9

What occurs during platelet aggregation?

Answer 9

Passing platelets are activated and stick to the growing mass of platelets causing many platelets to accumulate at the site of blood loss, forming a platelet plug.

Question 10

How is the intrinsic pathway of the clotting cascade activated?

Answer 10

By blood trauma - blood comes in contact with exposed collagen fibres of damaged endothelial cells or damaged platelets release phospholipids.

Question 11

How is the extrinsic pathway of the clotting cascade activated?

Answer 11

By tissue trauma when damaged cells release thromboplastin (tissue factor/factor three) into the blood.

Question 12

In the intrinsic pathway of the clotting cascade which two factors (in their active form) facilitate the activation of factor ten?

Answer 12

Factors 8 and 9

Question 13

What is the first factor to be activated in the intrinsic pathway?

Answer 13

Factor 12

Question 14

In the clotting cascade, what factor does factor 12 allow the activation of?

Answer 14

Factor 11

Question 15

In the clotting cascade, the activation of factor nine is facilitated by which clotting factor?

Answer 15

Factor eleven

Question 16

In the clotting cascade which factor does thromboplastin (factor 3) activate?

Answer 16

Factor seven

Question 17

In the extrinsic pathway of the clotting cascade which two factors combine (in their active forms) to facilitate the activation of factor ten?

Answer 17

Factors 3 and 7

Question 18

Which factor in the clotting cascade, indicates the merging of the intrinsic and extrinsic pathways?

Answer 18

Factor ten

Question 19

In the clotting cascade, with which factor does factor 10 combine to facilitate the activation of factor two?

Answer 19

Factor five

Question 20

What is the name of the enzyme formed by factors 5 and 10?

Answer 20

Prothrombinase

Question 21

Which factor catalyses the conversion of fibrinogen to insoluble monomers of fibrin?

Answer 21

Factor two / thrombin

Question 22

How do the fibrin monomers become polymers?

Answer 22

They spontaneously polymerise

Question 23

What is the process of dissolving the clot called and why does this happen?

Answer 23

Fibrinolysis - because at some point in the healing process the clot begins to block the oath of healing

Question 24

What factors lead to the activation of plasmin?

Answer 24

Factor 12, thrombin, tissue plasminogen activator

Question 25

What does plasmin do?

Answer 25

It is an enzyme that breaks down the fibrin threads of a blood clot and deactivates factors 1, 2, 5 and 12.

Question 26

Which clotting factors require the presence of calcium ions for their activation?

Answer 26

2, 10, 13

Question 27

What does factor 13 do in the clotting cascade?

Answer 27

It strengthens and stabilises the clot

Question 28

What factors/proteins involved in blood clotting require vitamin K for their synthesis?

Answer 28

Factors 2, 7, 9 and 10 | Proteins C, S and Z

Question 29

What does protein C do in blood clotting?

Answer 29

It inactivates factors five and thirteen and inactivates an inhibitor of plasminogen

Question 30

What does protein S do in blood clotting?

Answer 30

It is a cofactor of protein C that inhibits factors five and thirteen

Question 31

What does protein Z do in blood clotting?

Answer 31

It is involved in the degradation of factor ten

Question 32

Which factors does antithrombin inhibit?

Answer 32

Two, ten and the factor eight/nine complex

Question 33

What is the role of prostacyclin in the healing/clotting process?

Answer 33

Inhibits platelet adhesion

Question 34

Name two anticoagulants.

Answer 34

Heparin | Warfarin

Question 35

How does warfarin act as an anticoagulant?

Answer 35

It inhibits vitamin K reductase, stopping the production of factors two, seven, nine and ten in the liver

Question 36

Antithrombin III is a natural anticoagulant found in plasma. T/F?

Answer 36

True

Question 37

Haemophilia A is a deficiency of factor...?

Answer 37

8

Question 38

Haemophilia B is a deficiency of factor...?

Answer 38

Nine

Question 39

Haemophilia C is a deficiency of factor....?

Answer 39

Eleven

Question 40

On which chromosome are the genes for clotting factors 8,9 and 11?

Answer 40

X chromosome

Question 41

What is a deficiency of platelets called?

Answer 41

Thrombocytopenia

Question 42

When a vessel is damaged which platelet surface integrin permits adhesion to collagen via the von Willebrand factor bridge?

Answer 42

GPIb

Question 43

Binding of platelets to exposed collagen causes a shape change in platelets from what to what?

Answer 43

Discoid to spherical with the development of pseudopodia

Question 44

What surface integrin do activated platelets expose in order to form an aggregate?

Answer 44

GPIIb/GPIIIa

Question 45

Activated platelets produce thromboxane A2 which activates adjacent platelets and promotes vasoconstriction via which pathway?

Answer 45

Arachidonic acid

Question 46

Degranulation of platelets during platelet plug formation releases what molecules to promote platelet aggregation and vasoconstriction?

Answer 46

ADP | 5-HT

Question 47

Thrombosis in the coronary artery will lead to...?

Answer 47

MI

Question 48

Thrombosis in the cerebral artery leads to...?

Answer 48

Thrombotic stroke

Question 49

What is the name of a fragment of a thrombus which buds off?

Answer 49

Embolus