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PSL301 > Lecture 5: Blood Clotting > Flashcards

Lecture 5: Blood Clotting Flashcards

1
Q

What gives rise to platelets?

A

megakaryocytes

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2
Q

___ are needed for blood clotting

A

platelets

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3
Q

How do megakaryocytes give rise to platelets?

A

Edges of megakaryocyte break off to form platelets (cell fragments)

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4
Q

Megakaryocytes are…

A

giant cells with many copies of DNA in the nucleus

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5
Q

Half life of platelets?

A

10 days

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6
Q

____ increases platelet numbers by…

A

thrombopoietin

stimulating production of platelets

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7
Q

How is blood clotting regulated? (3 phases)

A
  1. vascular phase
  2. platelet phase
  3. coagulation phase
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8
Q

Vascular phase

A

Exposed collagen & tissue factors cause vasoconstriction of the damaged blood vessel. Vasoconstriction minimizes blood loss.

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9
Q

Vascular phase controlled by…

A

nervous system & muscles (neurogenic & myogenic control)

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10
Q

Vasoconstriction in vascular phase prolonged by…

A
  1. Serotonin
  2. Endothelin-1
  3. Thromoboxane A2
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11
Q

Platelet phase

A
  1. Collagen exposed to blood stream; bind platelets passing by in the blood
  2. Factors released from trapped platelets attract more platelets
  3. Platelets aggregate to form plug
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12
Q

What makes von Willebrand factor?

A

endothelial cells

platelets

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13
Q

What does von Willebrand factor bind to?

A

collagen

platelets

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14
Q

What are the factors released from platelets?

A

ADP
PAF (platelet activating factor)
serotonin
thromboxane

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15
Q

When are factors released from platelets?

A

during platelet phase

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16
Q

What does serotonin and thromboxane cause?

A

vasoconstriction

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17
Q

What do activated platelets look like?

A

spiky outer surface

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18
Q

Purpose of activating platelets?

A

they can adhere to each other better

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19
Q

What do inactivated platelets look like?

A

disk-like cell fragments

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20
Q

What prevents platelet adhesion/activation during normal situations?

A

Vasodilators:
NO
Prostacyclin

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21
Q

What releases NO and prostacyclin

A

endothelium

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22
Q

Prostacyclin is made up of…

A

Prostaglandin I2, PGI2

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23
Q

Why is aspirin given after mild heart attacks?

A

Precursor for thromboxane is arachidonic acid.
Enzyme cyclooxygenase cleaves ADA -> PGH2 -> thromboxane.
Aspirin stops CO activity, so thromboxane can’t be made.
Since thromboxane is used to vasoconstrict & aggregate platelets, these don’t happen as easily.

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24
Q

Function of von Willebrand factor?

A
  • link platelet with collagen
  • draw platelet into exposed collagen area
  • keep VII in circulation longer
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25
What happens during vascular phase?
vasoconstriction
26
What happens during platelet phase?
Platelets are actively trying to stop bleeding (loose platelet plug)
27
What happens during coagulation phase?
- Proper blood clot forms via coagulation cascade | - Fibrinogen -> fibrin
28
Fibrin
Long strand of fibre that reinforces loose platelet plug One piece of fibrinogen
29
Inactive form of fibrin
fibrinogen
30
What do all the factors released from platelets cause?
platelet aggregation
31
What are the effects of thromboxane?
Constriction | Platelet aggregation
32
Cyclooxygenase catalyses what reaction?
arachidonic acid -> PGH2
33
What can PGH2 become?
Prostaglandins Thromboxane Prostacyclin
34
Why is prostacyclin activity not affected when aspirin is taken?
Endothelial cells can still make more CO
35
What is the sturdiest form of fibrin?
covalent cross-links
36
What enzyme cleaves fibrinogen to fibrin?
thrombin
37
is fibrin soluble / insoluble?
insoluble
38
How does fibrin become cross-linked?
Factor XIII & Ca++ catalysed
39
Summary of coagulation cascade
1. Contact activation pathway 2. Tissue factor pathway 3. Common pathway 1->3 or 2->3
40
Intrinsic pathway
Contact activation pathway
41
extrinsic pathway
tissue factor pathway
42
trigger for intrinsic pathway
collagen in bld vessels exposed due to injury
43
What is the function of ADP?
Attract more platelets to damaged area
44
Trigger for extrinsic pathway
Damaged tissue exposes thromboplastin
45
What does factor XI and factor VII activate?
Factor X (common pathway)
46
What activates prothrombin activator?
``` Factor X Factor III Factor V Ca++ PF3 PL ```
47
Purpose of prothrombin activator?
prothrombin -> thrombin
48
What activates factor XIII?
Thrombin
49
What is the beginning of the common pathway?
active factor X
50
Where are many plasma factors used for blood clotting made?
liver
51
Cascade of intrinsic pathway
1. Exposed collagen activates factor XII 2. Factor XII & Ca++ activate Factor XI 3. Factor XI & Ca++ activate factor IX 4. Factor IX, factor VIII, Ca++, PL activate factor X
52
what regulates levels of factor VIII?
von Willebrand factor (keeps VIII around for longer)
53
Vit K needed for the synthesis of...
thrombin VII IX X
54
What drugs blocks the action of vit K?
Coumadin / Warfarin | -> less blood clotting
55
What vitamin helps blood clotting?
vit K
56
Cascade of extrinsic pathway
1. Factor III from thromboplastin activate Factor VII 2. VII + III activate IX 3. III and VII // Ca++ // PL -> activates X Positive feedback: X activates VII
57
vWf disease (symptoms)
problem with quality or quantity of vWf | problem with blood clotting
58
Which areas are most affected by the lack of vWf?
areas w/ small number of capillaries (skin, GI, uterus)
59
treatment for vWf disease?
protein that releases vasopressin to endothelial cells: stimulate release of vWf
60
Hemophilia A need to be injected with...
VIII
61
Hemophilia B due to deficiency in...
IX
62
Symptoms of hemophilia
internal and external bleeding that doesn't stop easily
63
which pathway is still active in those with haemophilia?
Extrinsic, but not enough to have normal blood clotting efficiency
64
Purpose of plasmin
fibrin -> fibrin fragments (easy to break up and remove)
65
Which enzymes are responsible for the formation of plasminogen -> plasmin?
Thrombin | tPA
66
What enzymes are used for fibrinolysis (anticoagulants)?
1. plasmin 2. tPa 3. TFPI 4. Antithrombin 5. Protein C
67
tPA released by...
damaged endothelium (released very slowly)
68
precursor of plasmin
plasminogen
69
Thrombin has positive feedback on...
1. VII activation 2. VIII activation 3. IX activation 4. XI activation 5. V activation
70
What activates protein C?
thrombin -> (catalysed by protein S)
71
function of protein C?
1. stop activation of VIII | 2. stop activation of V
72
function of TFPI?
stop VII activation
73
function of antithrombin?
1. stop IX activation 2. stop X activation 3. stop XI activation 4. stop XII activation 5. stop thrombin
74
TFPI
tissue factor pathway inhibitor
75
Where is plasminogen / plasmin released from?
liver
76
Where is tPA released from?
many tissues
77
Where is TFPI released from?
endothelium
78
Where is antithrombin released from?
liver
79
Where is protein c released from?
liver
80
tPA is activated by...
not activated
81
TFPI is activated by...
not activated
82
Antithrombin is activated by...
heparin
83
Haemorrhagic stroke
Blood vessel in brain bursts, and blood leaks into brain
84
Stroke
Blood clot gets stuck in artery going into brain
85
Thrombus
blood clot attached to vessel wall (less O gets to tissues)
86
Embolus
Floating blood clot
87
tPA
tissue plasminogen activator
88
What is a treatment for stroke?
tPA given within 3-4 after a stroke | this breaks down the blood clot
89
When is tPA not administered as a treatment for a stroke?
Haemorrhagic stroke | Will make the bleeding worse

PSL301 (29 decks)

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