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PPoS > Haemostasis #1 > Flashcards

Haemostasis #1 Flashcards

1
Q

What is haemostasis?

A
  • arrest of blood loss from damaged vessels

- active process that inhib/induces platelet activation

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2
Q

What are platelets like during haemostasis?

A
  • non-adhesive

- circulate singularly

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3
Q

What happens to platelets during vessel wall injury?

A
  • aggregate
  • become stabilised by fibrin
  • arrest bleeding from severed vessels (clotting)
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4
Q

What is thrombosis?

A

formation of occlusive thrombi leading to MI, ischaemic stroke

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5
Q

What does NO + prostacyclin (PGI2) do?

A
  • released by endo cell + can inhib platelet formation + sm cell activity
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6
Q

What does EDHF do?

A

released by endo cell + inhib sm cell activity

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7
Q

What does endothelin 1 (ET-1) do?

A

released by endo cell + activates sm activity

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8
Q

What does thromboxane (TXA2) do?

A

released by platelets + activates sm cell activity

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9
Q

Describe activation of platelets + vasoconstriction

A
  1. damage to blood vessel
  2. exposure of platelets to collage + von Willebrand factor in ECM of damaged blood vessel + later exposure to thromboxin
  3. causes platelets to adhere by adhesion mol to ECM + activate release of mediators
  4. cause vasoconstriction of blood vessel to stop blood loss + aggregation of platelets
  5. formation of soft platelet plug
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10
Q

What is the 1st part of the clotting pathway (simplified)?

A

initiation (used to be extrinsic as TF not normally present on damaged vasculature but becomes expressed when blood vessel damaged)

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11
Q

What is initiation activated by?

A

tissue factor

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12
Q

Where does initiation take place?

A

on TF-expressing cells in tissues after blood with clotting factors leaks out of vessels

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13
Q

What are clotting factors?

A

serine proteases

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14
Q

Describe process of initiation of clotting pathway (simplified)

A
  1. TF combines with FVII to prod activated FVIIa:TF complex
  2. activates FX to cause FXa
  3. FXa cause prothrombin (FII) to prod thrombin (FIIa)
  4. thrombin activates platelets which leads to amp + propagation of cascade
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15
Q

What is 2nd part of clotting pathway?

A

amp + propagation (used to be intrinsic as activated by cells normally found in blood vessels)

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16
Q

What does amp + prop involve?

A
  • initiated by thrombin

- involves activation of many factors: FV, FVIII, FIX, FX

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17
Q

Where does amp + prop take place?

A

on activated platelets surface

18
Q

Describe process of amp + prop of clotting pathway (simplified)

A
  1. FVa combines with FXa to cause amp of prod of thrombin

2. thrombin causes cleaving of fibrinogen to fibrin on surface of activated platelets to cause irrev clot

19
Q

What does sev of steps of clotting pathway involve?

A

Ca2+ + phospholipids

20
Q

What are key roles of FXa + FIIa?

A
  • accelarate cascade

- anti-coagulant drug targets

21
Q

Describe process of initiation of clotting pathway (detailed)

A
  1. TF in plasma combines with FVII to prod activated FVIIa:TF complex
  2. FX activated by complex, Ca2+ + phospholipid to cause FXa
  3. FXa combine with FVa to cause prothrombin (FII) to thrombin (FIIa)
  4. thrombin activates platelets which leads to amp of cascade
22
Q

Describe process of amplification of clotting pathway (detailed)

A
  • on platelet surface
    1. thrombin activates platelets - changes shape
    2. release of FV from alpha granules in platelets to be expressed on platelet surface to give FVa
    3. thrombin cleave FVIII-vWF complex to FVIIIa on platelet surface
    4. FVIIIa + FVa cause propagation of FIX to FIXa by TF:VIIa
23
Q

Describe process of propagation of clotting pathway (detailed)

A
  1. FIXa combine with FVIIIa:IXa (tenase) on platelet surface
  2. activates FX to form FXa:Va (prothrombinase)
  3. cleaved by prothrombin to thrombin
24
Q

What is effect of prop?

A

1000x more thrombin than initiation phase - stronger response

25
Q

What is not normally found in lumen of vas endo?

A

fibroblasts

26
Q

Describe process of fibrin deposition of clotting pathway

A
  1. fibrinogen expressed on GPIIa/IIIa receptors of activated platelets
  2. thrombin converts fibrinogen to fibrin + binds to it
  3. get mesh of fibrin through polym
  4. thrombin + FXIIIa cause cross-linking of fibrin to cause irrev/stable clot
27
Q

What is clot retraction?

A
  • red clot size

- clot contracts + dies out to form scar

28
Q

What is atherosclerosis?

A
  • vulnerable plaque formed in blood vessel with lipid rich core + fibrous cap
  • caused by poor diet + lack of exercise
29
Q

What is fibrous cap of stable plaque?

A

covers core to limit its size

30
Q

What happens in unstable coronary artery disease?

A
  • disruption of cap causes localised activation + acc of platelets
31
Q

What is downstream embolism?

A
  • if dynamic process of thombosis + thrombolysis goes wrong in coronary circ - ischaemia of heart cells which leads to MI/emboli lodged in brain cause stroke
  • if in pul circ, cause pul embolism
32
Q

How is haemostasis dynamic process?

A
  • pathways lead to thrombosis + thrombolysis
  • thrombosis = full occlusion of artery’s lumen
  • thrombolysis = prevent full occlusion
33
Q

What is Virchow’s triad?

A
  • predis to thrombosis:
    1. lower blood flow (more common in vein)
    2. endothelial disturbance/damage (more common in arteries)
    3. hyper blood coagulability - stasis if blood - lead to dec blood flow which dilutes coagulation proteins which inc risk of thrombosis
34
Q

What is arterial thrombosis (white clots) usually ass with?

A
  • atherosclerosis

- large platelet component

35
Q

Where do white clots form?

A

at site of vascular injury + disturbed blood flow

36
Q

How is arterial thrombosis treated?

A

prophylaxis with anti-platelet drugs

37
Q

What does arterial thrombosis cause?

A

MI + 80% strokes

38
Q

What is venous thrombosis ass with?

A
  • stasis/turbulent flow of blood
  • vascular injury following surgery/trauma of vessels
  • hypercoaguability of blood
39
Q

What do red clots contain?

A

RBC component

40
Q

What is treatment for venous thrombosis?

A

pro-phylaxis with anticoagulants

41
Q

What can venous thrombosis cause?

A

3rd leading cause of cardiovas ass death which leads to pul embolism

PPoS (11 decks)

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