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PHA112 > Haemostasis > Flashcards

Haemostasis Flashcards

1
Q

Define haemostasis

A

Body’s physiological response to prevent significant blood loss after vascular injury

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2
Q

List the 4 step process

A
  • Localised vasoconstriction
  • Primary haemostasis (platelet plug formation)
  • Secondary haemostasis (coagulation)
  • Tertiary haemostasis (fibrinolysis)
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3
Q

Describe each step of haemostasis

A

1st - Reduces blood flow to injury site + retards blood flow
2nd - Plugs breach in blood vessel
3rd - Strengthens + reinforces platelet plug
4th - dissolves clot once blood vessel integrity has been restored

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4
Q

List the 4 events that occur in primary haemostasis

A

Platelet adhesion + activation

Aggregation + plug formation

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5
Q

What changes occur during platelet activation

A
  • Change shape
  • Cytoplasmic granules released
  • Increase thromboxane A2
  • Activation + expression of GPIIb/IIIa receptors
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6
Q

Agonist - activated platelet GPIIb/IIIa receptors bind to ______ to form _____ with adjacent platelets to form a primary haemostatic plug. This can stop haemorrhage in _____ blood vessels.

A

Fibrinogen
Cross-bridges
Small

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7
Q

Activated + aggregated platelets form the phospholipid membrane surface for _____

A

Clotting

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8
Q

What are the 3 pathways of the coagulation cascade?

A

Extrinsic, intrinsic, common

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9
Q

Major activation of the cascade requires what?

A
  • Very charged phospholipid-rich membrane
  • Enzyme
  • Substrate
  • Cofactor
  • Ca 2+
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10
Q

What is the coagulation cascade?

A

A sequence of enzymatic reactions involving blood borne coagulation factors

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11
Q

What is the final substrate of the cascade?

A

Fibrinogen

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12
Q

Fibrinogen is converted into ____ by the enzyme ____

A

Fibrin

Thrombin

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13
Q

Where are the main coagulation factors synthesised?

A

Liver

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14
Q

Is extrinsic a quick/slow response?

A

Quick

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15
Q

Is intrinsic a quick/slow response?

A

Slow

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16
Q

Which tissue factor is exposed at damaged tissue? (extrinsic pathway)

A

FIII

17
Q

What does prothrombin FII require for synthesis?

A

Require vit K for synthesis

18
Q

In the extrinsic pathway the released TF forms a complex with _____ and _____ which is called the _______. This activates _____ of the ________ and _______ pathway.
Activation of FX leads to the production of ______.

A 
FVII
Ca 2+
extrinsic tenase
FX
intrinsic 
common
thrombin
19
Q

In the intrinsic pathway, FXII forms a complex with ______ and ______ on collagen, activating _____.
FXIIa activates ____. FXIa activates ______.

A 
HMW kininogen
Prekallikrein
FXII
FXI
FIX
20
Q

The intrinsic tenase activates _____ in the ______ pathway, leading to the production of _______.

A

FX
common
thrombin

21
Q

List the steps of the common pathway

A
  • Activation of FX
  • Conversion of prothrombin (FII) to thrombin (FIIa)
  • Cleavage of fibrinogen (FI) to fibrin (FIa)
  • Polymerisation + stabilisation of fibrin polymers by FXIII
22
Q

The prothrombinase complex converts ______ to ______

A

prothrombin

thrombin

23
Q

Give 2 limitations of the coagulation cascade

A
  • Doesn’t explain how blood clots in vivo

- Assumes intrinsic + extrinsic are independently capable of clot formation

24
Q

Name the 3 steps of the new proposed model

A

Initiation
Propagation
Amplification

25
Q

What are the 2 cells required?

A

TF-bearing cells

Platelets

26
Q

Describe the 3 steps of fibrinolysis

A
  • Release of plasminogen activators
  • Plasmin production
  • Clot lysis + release of degradation products
27
Q

How is regulation of haemostasis achieved?

A

Combination of multiple endogenous antithrombotic & antifibrinolytic systems

28
Q

What are the general regulators of haemostasis?

A 
Endothelium
Plasma proteins (protease inhibitors)
29
Q

Why should the fibrinolytic system be regulated?

A

To ensure removal of unwanted fibrin clots & preservation of fibrin in wounds

30
Q

How many coagulation factors are there?

A

12

31
Q

What determines how coagulation factors are identified with roman numerals?

A

order of discovery

32
Q

What is fibrinolysis?

A

Dissolves and removes fibrin clot

33
Q

What proteolytic enzyme mediates fibrinolysis?

A

Plasmin

PHA112 (16 decks)

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