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Blood > Haemostasis and the Clotting Cascade > Flashcards

Haemostasis and the Clotting Cascade Flashcards

1
Q

What is haemostasis?

A

The process by which haemorrhage is prevented following tissue damage.

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2
Q

What are the three steps of haemostasis?

A

Vascular Spasm
Platelet Plug Formation
Coagulation

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3
Q

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

A

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

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4
Q

What causes the vascular spasm?

A

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

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5
Q

What are the three stages of platelet plug formation?

A

Platelet adhesion
Platelet release reaction
Platelet aggregation

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6
Q

What do platelets bind to in platelet adhesion?

A

Exposed collagen and connective tissue of the damaged blood vessel

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7
Q

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

A

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.

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8
Q

What happens during the platelet release reaction?

A

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

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9
Q

What occurs during platelet aggregation?

A

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.

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10
Q

How is the intrinsic pathway of the clotting cascade activated?

A

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

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11
Q

How is the extrinsic pathway of the clotting cascade activated?

A

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

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12
Q

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

A

Factors 8 and 9

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13
Q

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

A

Factor 12

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14
Q

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

A

Factor 11

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15
Q

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

A

Factor eleven

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16
Q

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

A

Factor seven

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17
Q

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

A

Factors 3 and 7

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18
Q

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

A

Factor ten

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19
Q

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

A

Factor five

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20
Q

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

A

Prothrombinase

21
Q

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

A

Factor two / thrombin

22
Q

How do the fibrin monomers become polymers?

A

They spontaneously polymerise

23
Q

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

A

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

24
Q

What factors lead to the activation of plasmin?

A

Factor 12, thrombin, tissue plasminogen activator

25
Q

What does plasmin do?

A

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

26
Q

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

A

2, 10, 13

27
Q

What does factor 13 do in the clotting cascade?

A

It strengthens and stabilises the clot

28
Q

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

A

Factors 2, 7, 9 and 10

Proteins C, S and Z

29
Q

What does protein C do in blood clotting?

A

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

30
Q

What does protein S do in blood clotting?

A

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

31
Q

What does protein Z do in blood clotting?

A

It is involved in the degradation of factor ten

32
Q

Which factors does antithrombin inhibit?

A

Two, ten and the factor eight/nine complex

33
Q

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

A

Inhibits platelet adhesion

34
Q

Name two anticoagulants.

A

Heparin

Warfarin

35
Q

How does warfarin act as an anticoagulant?

A

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

36
Q

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

A

True

37
Q

Haemophilia A is a deficiency of factor…?

A

8

38
Q

Haemophilia B is a deficiency of factor…?

A

Nine

39
Q

Haemophilia C is a deficiency of factor….?

A

Eleven

40
Q

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

A

X chromosome

41
Q

What is a deficiency of platelets called?

A

Thrombocytopenia

42
Q

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

A

GPIb

43
Q

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

A

Discoid to spherical with the development of pseudopodia

44
Q

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

A

GPIIb/GPIIIa

45
Q

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

A

Arachidonic acid

46
Q

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

A

ADP

5-HT

47
Q

Thrombosis in the coronary artery will lead to…?

A

MI

48
Q

Thrombosis in the cerebral artery leads to…?

A

Thrombotic stroke

49
Q

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

A

Embolus

Blood (6 decks)

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