Haemostasis

Question 1

Define haemostasis

Answer 1

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

Question 2

List the 4 step process

Answer 2

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

Question 3

Describe each step of haemostasis

Answer 3

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

Question 4

List the 4 events that occur in primary haemostasis

Answer 4

Platelet adhesion + activation

Aggregation + plug formation

Question 5

What changes occur during platelet activation

Answer 5

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

Question 6

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.

Answer 6

Fibrinogen
Cross-bridges
Small

Question 7

Activated + aggregated platelets form the phospholipid membrane surface for _____

Answer 7

Clotting

Question 8

What are the 3 pathways of the coagulation cascade?

Answer 8

Extrinsic, intrinsic, common

Question 9

Major activation of the cascade requires what?

Answer 9

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

Question 10

What is the coagulation cascade?

Answer 10

A sequence of enzymatic reactions involving blood borne coagulation factors

Question 11

What is the final substrate of the cascade?

Answer 11

Fibrinogen

Question 12

Fibrinogen is converted into ____ by the enzyme ____

Answer 12

Fibrin

Thrombin

Question 13

Where are the main coagulation factors synthesised?

Answer 13

Liver

Question 14

Is extrinsic a quick/slow response?

Answer 14

Quick

Question 15

Is intrinsic a quick/slow response?

Answer 15

Slow

Question 16

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

Answer 16

FIII

Question 17

What does prothrombin FII require for synthesis?

Answer 17

Require vit K for synthesis

Question 18

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 ______.

Answer 18

FVII
Ca 2+
extrinsic tenase
FX
intrinsic 
common
thrombin

Question 19

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

Answer 19

HMW kininogen
Prekallikrein
FXII
FXI
FIX

Question 20

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

Answer 20

FX
common
thrombin

Question 21

List the steps of the common pathway

Answer 21

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

Question 22

The prothrombinase complex converts ______ to ______

Answer 22

prothrombin

thrombin

Question 23

Give 2 limitations of the coagulation cascade

Answer 23

• Doesn’t explain how blood clots in vivo

- Assumes intrinsic + extrinsic are independently capable of clot formation

Question 24

Name the 3 steps of the new proposed model

Answer 24

Initiation
Propagation
Amplification

Question 25

What are the 2 cells required?

Answer 25

TF-bearing cells | Platelets

Question 26

Describe the 3 steps of fibrinolysis

Answer 26

- Release of plasminogen activators - Plasmin production - Clot lysis + release of degradation products

Question 27

How is regulation of haemostasis achieved?

Answer 27

Combination of multiple endogenous antithrombotic & antifibrinolytic systems

Question 28

What are the general regulators of haemostasis?

Answer 28

``` Endothelium Plasma proteins (protease inhibitors) ```

Question 29

Why should the fibrinolytic system be regulated?

Answer 29

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

Question 30

How many coagulation factors are there?

Answer 30

12

Question 31

What determines how coagulation factors are identified with roman numerals?

Answer 31

order of discovery

Question 32

What is fibrinolysis?

Answer 32

Dissolves and removes fibrin clot

Question 33

What proteolytic enzyme mediates fibrinolysis?

Answer 33

Plasmin