Blood Coagulation

Question 1

Blood coagulation define :

Answer 1

Process by which blood changes from a liquid to a gel, forming a blood clot

Question 2

Heamostasis define

Answer 2

Process enables the cessation of bleeding in response to vascular injury
Prevents blood loss + enables tissue repair

Question 3

Thrombosis define:

Answer 3

Blood clots are formed when they are not needed; limit/ block blood flow (normally in vein)
Blood clot=thrombus

Question 4

Embolism define:

Answer 4

When a thrombus breaks loose and travels from one location in the body to another: blood clot=embolism

Question 5

Haemostasis steps

Answer 5

Blood vessel injury

Primary haemostasis =vasoconstriction + platelet plug formation
Secondary haemostasis = stable clot formation : coagulation cascade activation
Fibrinolysis/tertiary haemostasis = vessel repair and dissolution of clot

Question 6

Primary haemostasis what happens simplified:

Answer 6

Vasoconstriction- reduces blood flow therefore reduces blood loss
Platelet plug formation- involving platelet adhesion, activation, aggregation

Question 7

Steps in platelet plug formation:

Answer 7

Platelet adhesion
Platelet activation
Platelet aggregation

Question 8

Platelet life span:

Answer 8

7-10 days
150,000-400,000 platelets per micro litre of blood

Question 9

Platelet plug formation: adhesion explain

Answer 9

Breach of endothelial cells = exposure of collagen
vWF (von Willebrand factor) binds to collagen
GPIb-V-IX binds to vWF immobilised on collagen
GPVI and GPIa/IIa (a2B1) binds to exposed collagen

Question 10

Platelet plug formation: Activation

Answer 10

Platelets change shape
Release vWF,fibrinogen,ADP, TXA2
ADP( binds to P2Y12 receptors on platelets) and TXA2 bind to TXA2 receptors on platelets ; both activating GPIIb/IIIa

Question 11

Platelet plug formation: aggregation

Answer 11

Activation of GPIIb/IIIa receptor

GPIIb/IIIa binds to fibrinogen
GPIIb/IIIa vWF
=Bridges between platelets / aggregation

Question 12

Coagulation factors : what does a mean? X to Xa

Answer 12

X= inactive precursor
Xa= active

Question 13

Secondary haemostasis simplified

Answer 13

Stable clot formation; coagulation cascade activation- end result is the activation of thrombin which :
- converts fibrinogen to fibrin
- induces more platelet recruitment and activation

Question 14

Pathways in coagulation cascade

Answer 14

Extrinsic / Tissue factor pathway
Intrinsic / Contact pathway
Common pathway

Question 15

coagulation cascade: Extrinsic / Tissue factor pathway what happens?

Answer 15

Activated by ‘extrinsic’ factors- exposure of endothelial TF following injury
III (Tissue factor) interacts with factor VII to activate= VIIIa to activate factor X to Xa = extrinsic tenase complex

Question 16

factor VII to activate= VIIIa needs?

Answer 16

Vitamin K
And tissue factor (III) -when in blood

Question 17

coagulation cascade:Intrinsic/ Contact pathway what happens?

Answer 17

Activated by ‘intrinsic’ factors present in blood
Factor XII —> XIIa which activates factor XI to XIa which activates IX to IXa
Then intrinsic tenase complex

Question 18

Intrinsic tenase complex

Answer 18

Factor XIa activates IX (to IXa) which combines with VIIa to activate Factor X —> Xa

Question 19

Extrinsic tease complex

Answer 19

III (Tissue factor) interacts with factor VII to activate= VIIIa to activate factor X to Xa

Question 20

Prothrombinase complex

Answer 20

Factor Xa , Va and Calcium bind together

Question 21

Prothrombinase complex activates?

Answer 21

Prothrombin (factor II ) into thrombin (factor IIa)

Question 22

coagulation cascade:Common pathway what happens?

Answer 22

May result after the activation of factor X at the end of either pathway.
Prothrombinase complex formed = activates prothrombin (factor II) into thrombin (factor IIa).
Thrombin (IIa) activates factor I (fibrinogen) to Ia (fibrin). Which binds to XIIIa to form cross-linked fibres

Question 23

Factor IIa (thrombin) can also bind to? (Despite factor I)

Answer 23

PPAR receptor on platelets —> platelet activation/aggregation

Question 24

Important brakes on the coagulation cascade

Answer 24

Look notes

Question 25

Fibrinolysis

Answer 25

To break down fibrin

Question 26

Tertiary haemostasis

Answer 26

Fibrinolysis
Thrombolysis
Tissue plasminogen Activator factor (t-PA) -PRODUCED BY ENDOTHELIAL CELLS
Convert plasminogen to plasmin
Factor Ia(fibrin) converted to fibrin degradation products

Question 27

Haemostatic balance

Answer 27

Equilibrium between pro-coagulant/pro-thrombothic and anticoagulant /anti- thrombothic factors

Question 28

Pro-thrombin factors and anti-thrombotic factors

Answer 28

Pro-thrombin factors: increase in coagulation, platelets or decrease in Fibrinolysis

anti-thrombotic factors: decrease in coagulation, platelets or increase in Fibrinolysis

Question 29

Haemostasis disbalance when there is more anti-thrombotic factors leads to?

Answer 29

Bleeding

Question 30

Haemostasis disbalance when there is more pro-thrombotic factors leads to?

Answer 30

Thrombosis

Question 31

Arterial thrombus vs venous thrombus

Answer 31

Arterial thrombus- white; large platelet component

Venous thrombus- red; large fibrin component and rbcS

Question 32

Factors contributing to thrombosis

Answer 32

Described in Virchow’s triad
Hypercoagulability + vascular damage + circulatory stasis

If you have all 3= high risk at developing a thrombus

Question 33

What serious medical problems caused by clots?

Answer 33

Venous thromboembolism (VTE)
-deep vein thrombosis
-pulmonary embolism
Heart attack from atherosclerosis
Stroke from atrial fibrillation