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CR2 > 7 - Haemostasis Basics > Flashcards

7 - Haemostasis Basics Flashcards

1
Q

5 main components of haemostasis

A 
Platelets
Von Willebrand Factor
Tissue Factor
Clotting Proteins
Anticoagulant proteins
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2
Q

Primary haemostasis

A

Platelets and vasoconstriction form platelet plug

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3
Q

Thrombocytopenia

A

Below 150x109 per litre

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4
Q

Thrombocytosis

A

Over 450x109 per litre

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5
Q

What are platelets released from

A

Megakaryocyte (can release 1000+ platelets)

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6
Q

What is the function of granules

A

Secrete proteins needed for a plug

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7
Q

4 steps of primary haemostasis

A

Vessel Injury
Platelet release reaction
Platelet aggregation
Vasoconstriction

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8
Q

What is the role of Von Willebrand Factor

A

Assists the platelets to attach to an injured site by binding to collagen and each other

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9
Q

What is released in the platelet release reaction and what is their function

A

Adenosine Phosphate - causes platelets to aggregate
Serotonin - Vasoconstriction
Thromboxin A2 - Vasoconstriction and platelet aggregation

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10
Q

Extrinsic pathway

A

When blood vessels are injured

1) TF reacts with F7 -> F7a
2) 7a converts F10 -> 10a

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11
Q

Intrinsic pathway

A

When clots form without tissue injury

1) F12 -> 12a
2) 12a activates 11 -> 11a
3) 11a activates 9 -> 9a
4) 9a and factor 8 convert 10 to 10a

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12
Q

Common Pathway

A

1) 10a turns prothrombin to thrombin

2) thrombin turns fibrinogen to fibrin

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13
Q

What is the amplification stage

A

The small amount of thrombin produced from the extrinsic pathway activates factors 5,7,8,11 and 13

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14
Q

What is the role of antithrombin

A

Thrombin produces antithombin which converts plasminogen to plasmin (destroys cross links in fibrin formed by factor 13) and stops X to Xa

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15
Q

Test for the extrinsic pathway

A

Prothrombin Time

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16
Q

Test for intrinsic pathway

A

Activated Partial Prothrombin Time

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17
Q

What are the normal values for bleeding time

A

3-10minutes

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18
Q

What is the normal range for INR

A

0.8-1.2

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19
Q

Haemophillia A

A

Deficiency of factor 8

20
Q

Haemophilia B

A

Deficiency of factor 9

21
Q

What holds plasminogen in it’s inactive form

A

alpha-2 antiplasmin

22
Q

D-dimer

A

Product of fibrin breakdown

Low levels indicate no thrombosis

23
Q

What structures to platelets contain to stop bleeding

A

Proteins on surface allow them to stick
Granules secrete proteins
Contain proteins to allow them to change shape

24
Q

How do platelets change their shape when activated

A

First like a plate
activated by contact with materials such as collagen (due to break in blood vessel wall)
Extend long filaments which interlock and erythrocytes can be trapped

25
Q

How long is platelet lifespan

A

8-14 days

removed by reticuloendothelial system

26
Q

Structure of platelet

A

Lipid bilayer + microtubular system
9 glycoproteins
Cell membrane receptors - GpIIb/IIIa, gbIb

27
Q

What does a dense granule contain

A

ADP and calcium

28
Q

What do alpha granules contain

A 
P selectin
PDGF
Factor V
VWF
Fibrinogen
29
Q

How is vWF bound to platelets and what does it do

A

Vessel injury
Platelets adhere to collagen + vWF via gb1b
gPIIb/IIIa exposed via vwf binding forms a second binding site for vwf
Fibrinogen bound to promote platelet aggregation

30
Q

GpIb deficiency

A

Bernard Soulier Syndrome

31
Q

GpIIb/IIIa deficiency

A

Glanzmann’s

32
Q

Treatment for vWF disease

A

DDAVP
Tranexamic acid
vWF containing concentrate

33
Q

Types of VWF disease

A

Type 1 - mild/moderate deficiency
Type 2 - present but defective
Type 3 - total absence

34
Q

Where is tissue factor and what is its function

A

Present on subendothelial tissue
Expressed by cells which are not normally exposed to flowing blood
Physical injury exposes TF to flowing blood
Initiates clotting via factor 7

35
Q

Role of vWF

A

vWF binds to GpIb, subsequent activation via G-protein –> shape change –> disc to sphere –> pseudopods–> complex of GpIb, IIbIIIa, vWF, fibrinogen

36
Q

vWF agonists

A 
collagen
ADP
thrombin
adrenaline
TXA2
37
Q

What does factor 10 need to turn prothrombin to thrombin

A

calcium

factor 5a

38
Q

What is the INR

A

Practical form of prothrombin time

39
Q

What INR do you aim for in patients taking warfarin

A

2-3

40
Q

Function of tissue plasminogen activator

A

Released from normal endothelial cells

Catalyses plasminogen to plasmin

41
Q

When is TPA released

A

when the wound has healed

no longer need a clot

42
Q

What other molecules affect plasmin

A
  • urokinase plasminogen activator, kallikrein, and factor XIIa
43
Q

What is the function of antithrombin

A

Inhibits thrombin, 9,10, 11
Member of serine protease inhibitors
Binds to heparan sulfate on vascular endothelium

44
Q

Function of vitamin C

A

Activated by thrombin
Serine protease
Inactivates 5 and 8

45
Q

Function vitamin S

A

cofactor for protein C (apc)

46
Q

What are vitamin C and S dependent on

A

Vitamin K

CR2 (34 decks)

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