HAEMOSTASIS Flashcards

1
Q

what is haemostasis

A

arrest of bleeding and maintenance of vascular patency

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2
Q

what is primary haemostasis

A

formation of a platelet plug

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3
Q

what is secondary haemostasis

A

formation of a fibrin clot

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4
Q

what 2 mechanisms moderate the haemostatic system

A

fibrinolysis and anticoagulation

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5
Q

how are platelets formed

A

budding off from megakaryocytes

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6
Q

what are platelets made of

A

negatively charged phospholipids

Ca2+ ions

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7
Q

do platelets have a nucleus

A

no - they are buds of cytoplasm rather than true cells

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8
Q

what is the lifespan of a platelet

A

7-10 days

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9
Q

give an example of an antiplatelet drug

A

aspirin

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10
Q

endothelial (vessel wall) damage exposes ____ and releases ____

A

collagen

VWF

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11
Q

how do platelets bind to VWF

A

they possess receptors

glycoprotein 1B

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12
Q

what happens following the initial binding of platelets to VWF

A

activation of platelets which involves a change of shape

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13
Q

release of ___ and ____ stimulates platelet aggregation and adhesion to form plug

A

ADP

thromboxane A2

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14
Q

how do platelets bind to eachother

A

glycoprotein 2B3A

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15
Q

give 3 causes of failure of platelet plug formation

A

vascular
platelet - reduced number or function
VWF - low or absent

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16
Q

what is the name for reduced platelets

A

thrombocytopenia

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17
Q

what are some s/s of platelet plug formation failure

A

bruising
purpura
mucosal bleeding - epistaxis, GI, conjunctival, menorrhagia
ICH

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18
Q

what should you look for in the eyes of someone with a suspected bleeding disorder

A

conjunctival / retinal haemorrhages

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19
Q

how can failed primary haemostasis be screened

A

platelet count

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20
Q

why do elderly patients bleed more easily

A

less collagen so less efficient haemostasis

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21
Q

what organ produces all the clotting factors involved in secondary haemostasis

A

liver

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22
Q

what are the vitamin K dependent factors

A

2 7 9 10

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23
Q

how do clotting factors bind to platelets

A

bind to Ca2+ ions

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24
Q

what factors are involved in the initiation of the fibrin clot

A

tissue factor - factor VIIa

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25
what factors are involved in the propagation of the fibrin clot
factor VIII - IXa
26
describe the intrinsic pathway of clotting
``` 12 - 12a II - IIa 9 - 9a 9a:8a 10 - 10a 10a:5a prothrombin - thrombin ```
27
what clotting factor is prothrombin
2 (II)
28
what clotting factor is thrombin
2a (IIa)
29
describe the extrinsic pathway of clotting
endothelial trauma --> tissue factor : factor 7a 10 - 10a 10a:5a prothrombin - thrombin
30
what pathway initiates clotting
extrinsic
31
what pathway propagates clotting
intrinsic
32
what causes fibrinogen --> fibrin
thrombin
33
give the name of a serine protease that blocks all pathways of the cascade
anti-thrombin III
34
what factor is involved in the stabilising of the fibrin clot
XIIIa (13)
35
what switches on protein C and S
thrombomodulin
36
active protein C negatively acts on what factors
5 (V) | 8 (VIII)
37
_____ amplifies the clotting cascade
thrombin
38
_____ uses thrombomodulin to switch roles and inhibit coagulation
thrombin
39
activated ____ has a negative feedback control
fibrin
40
what breaks down fibrin
plasmin
41
where are protein S and C found
surface of platelets
42
what inhibits factor VII - VIIa
tissue factor pathway inhibitor
43
what would cause failure of fibrin clot formation (3)
single clotting factor deficiency multiple clotting factor deficiency increased fibrinolysis
44
what activates plasminogen --> plasmin
tissue plasminogen activator (tPA)
45
what is something that fibrin is broken down to
D-dimer
46
what is an example of a single clotting factor deficiency
haemophilia
47
what factor is deficient in haemophilia a
factor VIII (8)
48
what factor is deficient in haemophilia b
factor IX (9)
49
what is DIC
disseminated intravascular coagulation - widespread clotting which depletes the clotting factors and platelets leading to widespread bleeding
50
what is fibrinolysis
clot breakdown
51
what is used to screen for fibrin clot formation problems
prothrombin time | activated partial thromboplastic time
52
with bleeding disorders you can get bleeding into ___ and ____
joints and muscles
53
what is thrombophilia
deficiency of naturally occurring anticoagulants
54
what are you increased likelihood of getting with thrombophilia
venous thrombosis
55
what are some examples of naturally occurring anticoagulants
serine protease inhibitors - antithrombin III | protein S and C
56
what measures the common pathway
thrombin time
57
what measures the extrinsic pathway
prothrombin time
58
what measures the intrinsic pathway
APPT
59
what vitamin is required to form collagen
vitamin C
60
why are purpuric rashes more common on lower limbs
oncotic pressure due to gravity pushes fluid (+blood) out of capillaries
61
megakaryocytes are derived from the same lineage as ___
RBCs
62
what measurement is good for warfarin monitoring
prothrombin time (factor VII)
63
what measurement is good for heparin monitoring
APTT (factor VIII/IXa)
64
what is the most common type of inherited thrombophilia
factor V leiden
65
heparin inhibits the activation of what factors
2 9 10 11
66
the activation of factor _ is where the extrinsic and intrinsic pathways meet
10
67
_____ inhibits ADP - platelet activator
ADPase
68
____ keeps the blood soluble and prevents platelet activation in normal conditions
prostacyclin