7. Haemostasis - Coagulation Cascade Flashcards

1
Q

what initiates coagulation cascade

A

Tissue factor (TF)

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2
Q

what does TF bind to when it comes into contact with circulating blood

A

binds with factor VII
= factor VIIa

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3
Q

what is a tenase complex

A

complex that allows cleavage of X into Xa
2 forms = extrinsic and intrinsic

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4
Q

what is extrinsic complex made up of

A
  • Factor VIIa (from before)
  • TF (from before as well)
  • FX (the thing that needs to be activated)
  • Ca2+ (as per usual)
  • Phospholipid (idek why)

= CONVERTS X INTO Xa
and also smalllll amount of factor IX made

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5
Q

after factor Xa is made, what else needs to be made

A

(trace) thrombin

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6
Q

how is thrombin made

A

Factor Xa with some Ca2+
and Prothrombin

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7
Q

how is the initiation process down regulated

A

by action of tissue factor pathway inhibitor
= inhibits FXa and TF/FVIIa complex

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8
Q

what needs to happen after initiation

A

amplification

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9
Q

amplification process

A
  • thrombin activates:
    > platelets - to enhance platelet plug
    > FVIII
    > FV
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10
Q

what is factor 5 a cofactor for

A

10

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11
Q

what is factor 8 a cofactor for

A

factor 9

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12
Q

what comes after amplification

A

propogation

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13
Q

first step of propgation

A

formation of intrinsic tenas complex

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14
Q

what is intrinsic tenase complex made up of

A
  • IXa
  • VIIIa (cuz is 9s cofactor)
  • FX (duh)
  • Ca2+
  • phospholipid

= produces lots more Xa
with no specific inhibitor unlike in the extrinsic

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15
Q

prothrombinase complex

A

after intrinsic tenase:
- Xa
- and its cofactor Va
- Prothrombinase
- Ca2+
- phospholipid

= forms THROMBIN in larger amounts than before

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16
Q

after burst of thrombin by prothrombinase complex, what does it activate

A
  • platelets
  • 5, 8 and 7 (which feedback into coagulation process)
  • factor 11
  • factor 13 into 13a
17
Q

what does 13a do

A

crosslinking of fibrin = stable fibrin clot

18
Q

which coagulation factors are vitamin K dependent

A

prothrombin
7
9
10

19
Q

what is the contact activation pathway

A

occurs alongside coagulation pathway
exposure of clotting fators to collagen

20
Q

what factors bind to collagen in the contact activation pathway

A
  • high molecular weight kinogen (HMWK)
  • prekallikrein
  • factor 11 = 11a (which has feedback effect of 9)
  • factor 12 = 12a
21
Q

thrombin’s cofactor

A

thrombomodulin

22
Q

what is platelet plug clot retraction

A
  • as platelet plug degranulates, fibrin will increase
  • and after few hrs, the plug is entirely made up of cross linked fibrin
23
Q

what is clot retraction mediated by

A

glycoproteins
(same ones that were involved in platelet adhesion)

24
Q
A