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CR2 > Haemostasis Basics > Flashcards

Haemostasis Basics Flashcards

1
Q

Hemostasis

A

Physiological process that stops bleeding at the site of an injury while maintaining normal blood flow elsewhere in the circulation

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2
Q

How does intact endothelium prevent blood coagulation

A

Smooth
Expresses anticoagulants, tissue factor pathway inhibitor, thrombomodulin, heparin like proteoglycan, ectonucleotidase, platelet inhibitors, nitric oxide, prostacyclin

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3
Q

What are the stages of homeostasis

A

Primary
Secondary
Tertiary

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4
Q

What occurs in primary haemostasis

A

Vasoconstriction
Platelet plug formation

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5
Q

What happens in secondary haemostasis

A

Coagulation cascade
Deposition and stabilisation of fibrin

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6
Q

What happens in tertiary haemostasis

A

Dissolution of fibrin clot

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7
Q

Steps of haemostasis

A

Vascular spasm
Platelet plug formation
Clot formation
Clot retraction
Fibrinolysis

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8
Q

vascular spasm

A

trauma to vessel wall triggers smooth muscle contraction

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9
Q

Vascular spasm

A

Trauma to vessel wall triggers smooth muscle contraction

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10
Q

What causes smooth muscles to contract in vascular spasm

A

Local myogenic spasm
Endothelium and platelets release vasoconstrictor substances
Nervous reflexes

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11
Q

What are platelets derived from

A

Bone marrow megakaryocytes

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12
Q

What is the diameter of a platelet

A

1-4 um

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13
Q

What is the reference range for platelets in blood

A

140-450 x 10^9

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14
Q

What is the lifespan of a platelet

A

8-14 days

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15
Q

What system removes platelets from circulation

A

Reticuloendothelial system

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16
Q

What granules are part of a platelet

A

Alpha
Delta

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17
Q

Where does the activated coagulation cascade occur in secondary haemostasis

A

Platelet membrane

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18
Q

What do delta dense granules in platelets do

A

Facilitate platelet adhesion
Facilitate vasoconstriction

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19
Q

What type of platelet granules contain ADP and serotonin

A

Delta dense granules

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20
Q

Which platelet granules contain vWF, factor v, platelet derived growth factor, and high molecular weight kininogen

A

Alpha granules

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21
Q

What processes are platelet contractile proteins involved in

A

Platelet activation
Platelet aggregation
Clot retraction

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22
Q

Stages of platelet plug formation

A

Adhesion of platelets to damaged surface
Activation of platelets
Aggregation of platelets

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23
Q

What do platelets bind to in primary haemostasis

A

Exposed subendothelial collagen in vessel wall
Subendothelial bound vWF

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24
Q

What mediates platelet adhesion

A

Platelet receptors

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25
Q

What molecule can platelets directly adhere to

A

Collagen

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26
Q

What does platelet receptor GP1A bind to

A

Collagen

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27
Q

What does platelet receptor GP1B bind to

A

Von willebrand factor

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28
Q

What does von willebrand factor do

A

Binds to platelets allowing the platelet to bind to collagen
Exposes GPIIB and GPIIIa
Complexes with factor viii preventing its degradation

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29
Q

What cells synthesise von willebrand factor

A

Endothelial cells
Megakaryocytes

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30
Q

Where is von willebrand factor stored

A

Subendothelial matrix
Plasma
Platelet alpha granules

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31
Q

What exposes GPIIB and GPIIIA on platelets

A

Von willebrand factor binding

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32
Q

What stages of haemostasis are apeffected by von willebrand disease

A

Primary
Secondary

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33
Q

How is von willebrand disease inherited

A

Autosomal

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34
Q

What does von willebrand disease cause

A

Deficient or defective von willebrand factor

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35
Q

What type of von willebrand disease creates a mild deficiency

A

Type 1

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36
Q

What type of von willebrand disease creates defective protein

A

Type 2

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37
Q

What type of von willebrand disease has absent protein

A

Type 3

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38
Q

What 3 things occur when platelets become activated

A

Shape change
Increase surface receptor expression
Release granule contents

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39
Q

What causes platelets to change shape when they activate

A

Release of intracellular Ca2+ stores

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40
Q

What are the cytoplasmic projections on activated platelets called

A

Pseudopods

41
Q

What substances do platelets release when activated

A

ADP
Serotonin
Thromoxane A2

42
Q

What receptors does ADP released from platelet granules bind to

A

P2Y1
P2Y12

43
Q

Which receptor causes intracellular ca2+ store release, platelet shape change, and transient aggregation when ADP binds to it

A

P2Y1

44
Q

What happens when ADP binds to P2Y12

A

Decreased adenyl cyclise -> decreased cAMP -> sustained aggregation

45
Q

Sustained platelet aggregation involves which receptor? P2Y1 or P2Y12

A

P2Y12

46
Q

What does thromoxane A2 do

A

Activates other platelets to induce platelet aggregation
Increases cytosolic calcium levels
Diffuses out of cell to enhance vasoconstriction

47
Q

What molecule mediates platelet aggregation

A

Fibrinogen

48
Q

How does fibrinogen form the platelet plug

A

Binds to GPIIb/IIIa on adjacent platelets

49
Q

Where is fibrinogen released from for platelet aggregation

A

Alpha granules

50
Q

How is primary haemostasis tested

A

Bleeding time

51
Q

What is a normal bleeding time result

A

1-3 mins

52
Q

What platelet count shows thrombocytopenia

A

<150000 cells/um

53
Q

Petechiae

A

Tiny purplish spots of blood in skin or mucosa

54
Q

What causes thrombocytopenia

A

Decreased platelet production
Increased platelet destruction
Increased platelet sequestration

55
Q

Bernard soulier syndrome

A

Quantitative or qualitative defects of platelet GPIb

56
Q

Glazmann’s thrombasthenia

A

Deficiency/ defective platelet GPIIB/IIIa

57
Q

What occurs in secondary haemostasis

A

hemostasis plug formed by trapping RBCs in loose mesh of fibrin

58
Q

How many pathways are involved in thrombin formation

A

3 - extrinsic intrinsic common

59
Q

What does thrombin do

A

Activates fibrinogen to fibrin

60
Q

Which vitamin is needed for maturation of factors 2, 9, and 10

A

Vitamin K

61
Q

Which pathway extrinsic coagulation

A

Intrinsic

62
Q

What is tissue factor

A

Integral Membrane protein in sub-endothelial tissue released in response to tissue injury

63
Q

When is tissue factor releases

A

Tissue injury

64
Q

What does FVII become when it binds to tissue factor

A

FVIIa

65
Q

What substances from the extrinsic pathway act on factor X to activate it

A

Factor VIIa, thromboplastin, calcium, phospholipids

66
Q

Where does factor Xa form a prothrombinase complex to generate thrombin

A

Extravascular tissue

67
Q

How is the extrinsic pathway dampened

A

Inhibiting factor VII

68
Q

Which factors are in the extrinsic pathway

A

7, 3(tissue factor)

69
Q

What factors are involved in the intrinsic pathway

A

12, 11, 9 8

70
Q

What molecule activates factor viii

A

Thrombin

71
Q

What molecules activate factor x from the intrinsic pathway

A

Factor IXa, factor VIIIa, platelet phospholipids, calcium

72
Q

What is factor VIII found in a complex with

A

Von willebrand factor

73
Q

What is required for sustained thrombin activation

A

Activation of intrinsic pathway

74
Q

Which pathway activates the intrinsic pathway

A

Extrinsic pathway

75
Q

What do factor V, factor X, and tissue phospholipids combine to form in the common pathway

A

Prothrombin activator

76
Q

What does the prothrombin activator do in the common pathway

A

Splits prothrombin to thrombin

77
Q

Which ion is needed for prothrombin activator to split prothrombin to thrombin

A

Calcium

78
Q

What molecule does thrombin act on to form fibrin

A

Fibrinogen

79
Q

What molecules does thrombin act on

A

Fibrinogen
Factor VIII

80
Q

Which molecule activates factor VIII

A

Thrombin

81
Q

What prevents aggregation of fibrinogen molecules

A

Fibrinogen molecules have Strong negative charge

82
Q

What causes blood to coagulate

A

Soluble fibrinogen converted to insoluble fibrin by thrombin

83
Q

What bonds form between fibrin monomers to form a soft clot

A

Hydrogen bonds

84
Q

What molecule mediates formation of a hard clot

A

Factor XIII

85
Q

What bonds form in a soft clot to make it a hard clot

A

Covalent bonds

86
Q

What pattern of inheritance is haemophilia

A

X linked

87
Q

Which factor is affected in haemophilia a

A

Viii

88
Q

What factor Is affected in haemophilia B

A

Factor IX

89
Q

What happens to a clot after formation

A

Contraction

90
Q

What causes clot contraction

A

Platelet contractile proteins

91
Q

What do platelet contractile proteins do

A

Compress fibrin mesh work to retract clot
Pulls edges of cut together

92
Q

What molecule breaks down fibrin to fibrin degradation products

A

Plasmin

93
Q

What activates plasminogen to plasmin in the fibrolite pathway

A

Plasminogen activator

94
Q

What measurement is uses to diagnose thrombosis

A

D-dimer concentration

95
Q

What is the D dimer reference range

A

0-300 ng/ml

96
Q

What tests are used to asses haemostasis

A

Blood count/ platelet count
Bleeding time
Clotting time
Prothrombin time
Activated partial thromboplastin time

97
Q

What is the expected result for clotting time

A

3-10 minutes

98
Q

What is the expected result for prothrombin time

A

12-15 secinds

99
Q

What is the expected result for activated partial thromboplastin time

A

30-50 seconds

CR2 (33 decks)

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