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Haemostasis Basics Flashcards

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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
What molecule can platelets directly adhere to
Collagen
26
What does platelet receptor GP1A bind to
Collagen
27
What does platelet receptor GP1B bind to
Von willebrand factor
28
What does von willebrand factor do
Binds to platelets allowing the platelet to bind to collagen Exposes GPIIB and GPIIIa Complexes with factor viii preventing its degradation
29
What cells synthesise von willebrand factor
Endothelial cells Megakaryocytes
30
Where is von willebrand factor stored
Subendothelial matrix Plasma Platelet alpha granules
31
What exposes GPIIB and GPIIIA on platelets
Von willebrand factor binding
32
What stages of haemostasis are apeffected by von willebrand disease
Primary Secondary
33
How is von willebrand disease inherited
Autosomal
34
What does von willebrand disease cause
Deficient or defective von willebrand factor
35
What type of von willebrand disease creates a mild deficiency
Type 1
36
What type of von willebrand disease creates defective protein
Type 2
37
What type of von willebrand disease has absent protein
Type 3
38
What 3 things occur when platelets become activated
Shape change Increase surface receptor expression Release granule contents
39
What causes platelets to change shape when they activate
Release of intracellular Ca2+ stores
40
What are the cytoplasmic projections on activated platelets called
Pseudopods
41
What substances do platelets release when activated
ADP Serotonin Thromoxane A2
42
What receptors does ADP released from platelet granules bind to
P2Y1 P2Y12
43
Which receptor causes intracellular ca2+ store release, platelet shape change, and transient aggregation when ADP binds to it
P2Y1
44
What happens when ADP binds to P2Y12
Decreased adenyl cyclise -> decreased cAMP -> sustained aggregation
45
Sustained platelet aggregation involves which receptor? P2Y1 or P2Y12
P2Y12
46
What does thromoxane A2 do
Activates other platelets to induce platelet aggregation Increases cytosolic calcium levels Diffuses out of cell to enhance vasoconstriction
47
What molecule mediates platelet aggregation
Fibrinogen
48
How does fibrinogen form the platelet plug
Binds to GPIIb/IIIa on adjacent platelets
49
Where is fibrinogen released from for platelet aggregation
Alpha granules
50
How is primary haemostasis tested
Bleeding time
51
What is a normal bleeding time result
1-3 mins
52
What platelet count shows thrombocytopenia
<150000 cells/um
53
Petechiae
Tiny purplish spots of blood in skin or mucosa
54
What causes thrombocytopenia
Decreased platelet production Increased platelet destruction Increased platelet sequestration
55
Bernard soulier syndrome
Quantitative or qualitative defects of platelet GPIb
56
Glazmann’s thrombasthenia
Deficiency/ defective platelet GPIIB/IIIa
57
What occurs in secondary haemostasis
hemostasis plug formed by trapping RBCs in loose mesh of fibrin
58
How many pathways are involved in thrombin formation
3 - extrinsic intrinsic common
59
What does thrombin do
Activates fibrinogen to fibrin
60
Which vitamin is needed for maturation of factors 2, 9, and 10
Vitamin K
61
Which pathway extrinsic coagulation
Intrinsic
62
What is tissue factor
Integral Membrane protein in sub-endothelial tissue released in response to tissue injury
63
When is tissue factor releases
Tissue injury
64
What does FVII become when it binds to tissue factor
FVIIa
65
What substances from the extrinsic pathway act on factor X to activate it
Factor VIIa, thromboplastin, calcium, phospholipids
66
Where does factor Xa form a prothrombinase complex to generate thrombin
Extravascular tissue
67
How is the extrinsic pathway dampened
Inhibiting factor VII
68
Which factors are in the extrinsic pathway
7, 3(tissue factor)
69
What factors are involved in the intrinsic pathway
12, 11, 9 8
70
What molecule activates factor viii
Thrombin
71
What molecules activate factor x from the intrinsic pathway
Factor IXa, factor VIIIa, platelet phospholipids, calcium
72
What is factor VIII found in a complex with
Von willebrand factor
73
What is required for sustained thrombin activation
Activation of intrinsic pathway
74
Which pathway activates the intrinsic pathway
Extrinsic pathway
75
What do factor V, factor X, and tissue phospholipids combine to form in the common pathway
Prothrombin activator
76
What does the prothrombin activator do in the common pathway
Splits prothrombin to thrombin
77
Which ion is needed for prothrombin activator to split prothrombin to thrombin
Calcium
78
What molecule does thrombin act on to form fibrin
Fibrinogen
79
What molecules does thrombin act on
Fibrinogen Factor VIII
80
Which molecule activates factor VIII
Thrombin
81
What prevents aggregation of fibrinogen molecules
Fibrinogen molecules have Strong negative charge
82
What causes blood to coagulate
Soluble fibrinogen converted to insoluble fibrin by thrombin
83
What bonds form between fibrin monomers to form a soft clot
Hydrogen bonds
84
What molecule mediates formation of a hard clot
Factor XIII
85
What bonds form in a soft clot to make it a hard clot
Covalent bonds
86
What pattern of inheritance is haemophilia
X linked
87
Which factor is affected in haemophilia a
Viii
88
What factor Is affected in haemophilia B
Factor IX
89
What happens to a clot after formation
Contraction
90
What causes clot contraction
Platelet contractile proteins
91
What do platelet contractile proteins do
Compress fibrin mesh work to retract clot Pulls edges of cut together
92
What molecule breaks down fibrin to fibrin degradation products
Plasmin
93
What activates plasminogen to plasmin in the fibrolite pathway
Plasminogen activator
94
What measurement is uses to diagnose thrombosis
D-dimer concentration
95
What is the D dimer reference range
0-300 ng/ml
96
What tests are used to asses haemostasis
Blood count/ platelet count Bleeding time Clotting time Prothrombin time Activated partial thromboplastin time
97
What is the expected result for clotting time
3-10 minutes
98
What is the expected result for prothrombin time
12-15 secinds
99
What is the expected result for activated partial thromboplastin time
30-50 seconds

CR2 (33 decks)

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