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Cardiorespiratory CC > Haemostasis Basics > Flashcards

Haemostasis Basics Flashcards

1
Q

Haemostasis

A

The cessation of bleeding at a vascular injury site via the formation of a thrombus

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2
Q

Platelet Plug

A

Primary haemostasis
Circulating platelets form physical plug
Adhere to injury site + each other
Stop leak

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3
Q

Fibrin Clot

A

Secondary haemostasis
Assembly + activation of series of coagulation factor proteases
Cause thrombin production

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4
Q

Thrombin

A

Produces fibrin monomers

Can cross link together to form stabilised protein meshwork around plug

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5
Q

Platelets derivation

A

Megakaryocyte

1 megakaryocyte= over 1000 platelets

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6
Q

Platelets structure

A

no nucleus

1-4microm

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7
Q

Platelet circulation time

A

8.5-10 days

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8
Q

Platelet half life

A

4 days

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9
Q

Platelet production regulation

A

Thrombopoietin

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10
Q

Platelet level normal

A

150-400 x10(9) per litre

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11
Q

Thrombocytopenia

A

Platelets below 150x10(9) per litre

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12
Q

Thrombocytosis

A

Platelet above 400x10(9) per litre

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13
Q

Platelet adhesion prevention

A

NO and PGI2 (prostacyclin) release

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14
Q

What happens when endothelium exposed

A

NO production stops

Collagen under endothelium exposed

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15
Q

VWF

A

Protein in blood

Binds to exposed collagen

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16
Q

Receptor which helps bind platelets to VWF

A

Platelet GP1b receptor

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17
Q

Platelet GP2b/3a receptor

A

Expressed by adherent platelets
Binds to fibrinogen
Fibrinogen binds to more platelets to form meshwork

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18
Q

Platelet aggregation pathway

A 
Endothelium exposed
NO production stops
Collagen under endothelium exposed
VWF binds to collagen
Platelets bind to VWF via GP1b receptors
Platelets express GP2b/3a receptor
Receptor binds to fibrinogen
Meshwork formed
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19
Q

Bound platelet changes

A

Become spiky + change shape

Release ADP, TXA2 and 5HT

20
Q

ADP + TAX2 effect

A

Attract more platelets to the site

Aggregate to form platelet plug

21
Q

5HT effect

A

Acts on local smooth muscle

Vasoconstriction

22
Q

Bleeding time test

A

Normally stops 1-9mins
Children 1-13 mins
F>M

23
Q

Plug spread prevention

A

Healthy endothelium next to damaged site releases NO

24
Q

Extrinsic pathway

A

Triggers coagulation after vessel injury

25
Q

Factor VII

A

Plasma protein

26
Q

Factor III + Factor VII

A

Factor III exposed when blood vessel injured

Factor III converts VII–> VIIa

27
Q

Factor III (tissue factor)

A

Intracellular in endothelium and smooth muscle

28
Q

Factor VIIa

A

Reacts with Ca and Factor X to form Xa

29
Q

Xa and Ca

A

Prothrombin –> thrombin

30
Q

Common pathway

A

Prothrombin –> thrombin

31
Q

prothrombin time

A

Assesses extrinsic + common pathway

32
Q

Activate partial prothrombin time

A

assesses intrinsic and common pathway

33
Q

INR

A

Number derived from PT
0.8-1.2
Used to assess coagulability of patients on heparin or warfarin

34
Q

haemophilia A

A

Deficiency factor VIII

35
Q

Haemophilia B

A

Deficiency factor IX

36
Q

Plasmin

A

removal of clots when damaged tissue healed

37
Q

Plasminogen inactive form

A

Held by alpha-2 antiplasmin

38
Q

tPA

A

Released from endothelial cells

Catalyses plasminogen –> plasmin

39
Q

D-dimer

A

production of fibrin breakdown

40
Q

Low D-dimer levels

A

indication thrombosis not present

41
Q

Vitamin K deficiency

A

Increased INR

Unstable clots

42
Q

Heparin

A

Activates anti-thrombin
AT inhibits thrombin + factor Xa
IV as not absorbed by gut
Short half life

43
Q

Warfarin

A

Competes with sites that bind Vit K
Reduces effectiveness of clotting factors especially Factors VII, IX and X
Increases prothrombin time

44
Q

Daibigatran

A

Direct thrombin inhibitor

45
Q

Rivaroxaban, apixaban, edoxaban

A

factor Xa inhibitors

Cardiorespiratory CC (34 decks)

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