7. Haemostasis - Coagulation Cascade

Question 1

what initiates coagulation cascade

Answer 1

Tissue factor (TF)

Question 2

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

Answer 2

binds with factor VII
= factor VIIa

Question 3

what is a tenase complex

Answer 3

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

Question 4

what is extrinsic complex made up of

Answer 4

• 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

Question 5

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

Answer 5

(trace) thrombin

Question 6

how is thrombin made

Answer 6

Factor Xa with some Ca2+
and Prothrombin

Question 7

how is the initiation process down regulated

Answer 7

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

Question 8

what needs to happen after initiation

Answer 8

amplification

Question 9

amplification process

Answer 9

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

Question 10

what is factor 5 a cofactor for

Answer 10

10

Question 11

what is factor 8 a cofactor for

Answer 11

factor 9

Question 12

what comes after amplification

Answer 12

propogation

Question 13

first step of propgation

Answer 13

formation of intrinsic tenas complex

Question 14

what is intrinsic tenase complex made up of

Answer 14

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

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

Question 15

prothrombinase complex

Answer 15

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

= forms THROMBIN in larger amounts than before

Question 16

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

Answer 16

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

Question 17

what does 13a do

Answer 17

crosslinking of fibrin = stable fibrin clot

Question 18

which coagulation factors are vitamin K dependent

Answer 18

prothrombin
7
9
10

Question 19

what is the contact activation pathway

Answer 19

occurs alongside coagulation pathway
exposure of clotting fators to collagen

Question 20

what factors bind to collagen in the contact activation pathway

Answer 20

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

Question 21

thrombin’s cofactor

Answer 21

thrombomodulin

Question 22

what is platelet plug clot retraction

Answer 22

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

Question 23

what is clot retraction mediated by

Answer 23

glycoproteins
(same ones that were involved in platelet adhesion)