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HOS Unit 3 > 4 Mechanisms of Hemostasis > Flashcards

4 Mechanisms of Hemostasis Flashcards

1
Q

What is the mechanism by which bleeding is controlled after injury?

A

Hemostasis

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2
Q

Pathological states of hemostasis can lead to what 2 things?

A

thrombosis or hemorrhage

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3
Q

What cells play a vital role in hemostasis?

A

endothelial

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4
Q

damage to endothelium leads to what?

A

platelet adherence, aggregation and adherence

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5
Q

What happens at platelet activation?

A

release granules, increased intracellular Ca and decreased cAMP

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6
Q

What provides the phospholipid substrate on much of fluid phase coagulation occurs?

A

platelets

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7
Q

Plasma coagulation causes?

A

solubule FIBRINOGEN becomes insoluble cross-linked polymer FIBRIN

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8
Q

What type of enzymes need to be activated for fluid phase coagulation?

A

serine proteases

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9
Q

Where are coagulation factors produced?

A

liver

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10
Q

Breakdown of a clot requires what?

A

plasmin generation from plasminogen (fibrinolysis)

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11
Q

Decreasing clot formation is initiated by what?

A

antithrombin

Protein C and S pathways

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12
Q

Where does much of the interaction of plasma proteins occur?

A

on the surface of platelets

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13
Q

Coagulation occurs by interactions of what three things?

A

plasma proteins
platelets
tissue factor

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14
Q

What happens to arterioles right after injury?

A

vasoconstriction- brief, reflex mechanisms

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15
Q

What part of hemostasis is formation of platelet plug? fibrin clot?

A

Primary Hemostasis and Secondary Hemostasis

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16
Q

How long do platelets circulate in the blood?

A

7-10 days

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17
Q

What provides an enormous expansion of the surface area/volume ratio in platelets?

A

open canalicular system

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18
Q

What recruits adjacent platelets to form a plug?

A

alpha and dense granules

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19
Q

What are 5 basic events in series of platelet reaction?

A
  1. adhesion
  2. activation
  3. Release Reaction
    4, clot formation and retraction
  4. support plasma coagulation
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20
Q

Platelet adhesion requires what factor?

A

plasma protein von Willebrand factor (vWf) and of course the membrane receptor for it (Ib-IX-V)

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21
Q

Where is von willebrand factor produced and stored?

A

produced and stored in endothelial cell and megakaryocytes

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22
Q

T-F - platelets have vWf in there alpha granules?

A

True

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23
Q

what are the 3 functions of vWf?

A

bind platelet receptor
bind collagen
stabilize factor VIII

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24
Q

What binds to glycoprotein IIb-IIIa?

A

fibrinogen

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25
T-f- after activations platelets do not change shape?
False-become spherical spiny due to ADP receptors
26
What do dense granules contain?
ATP, ADP, calcium, serotonin
27
What do alpha granules contain?
coagulation factors growth modulators adhesive proteins
28
T-F - platelet granules also contain lysozymes
True
29
What does release of granule contents cause?
vasoconstriction, modulation of growth of vessel, cell adhesion, fluid phase coagulation
30
What generates arachidonic acid?
phospholipids acted upon by Phospholipase C.
31
What converts arachidonic acid to cyclic endoperoxide?
cyclo-oxygenase
32
What becomes of the endoperoxides?
prostoglandins | or Thromboxane A2
33
The secretion of platelet alpha granules leads to high concentrations of fibrinogen, factors V, VIII, XI, XIII which lead to and enhance what?
fibrin formation and stabilization
34
True or False- platelets have similarities of embryonic muscle?
True- actin myosin in platelets which organize filopodia
35
What do the platelet filopodias bind to?
fibrin and then contract to pull close together- drawing together the edges of the injured tissue.
36
What inhibits platelet aggregation
prostacyclin- made by endothelial cells | NO- also made from endothelial cells
37
Abnormal bleeding does not occur above what platelet count? troublesome bleeding?
>100x10^9 | <50x10^9
38
What factor is the main factor of activation from prothrombin to thrombin
Factor Xa
39
The final product of the coagulation cascade is fibrinogen to fibrin which is then cross linked by which factor?
XIII
40
What initiates the coagulation cascade in vivo?
tissue factor
41
What type of cell produces most of the coagulation factors? Exceptions?
hepatocytes--- - -exception VIII- liver endothelial cells - - exception vWf- endothelial cells and megakaryocytes
42
What must PROTHROMBIN(II), VII, IX, X, protein C and S have in order to be fully functional?
Vitamin K
43
Where does most of the Vitamin K we need come from?
gastrointestinal tract by bacteria
44
What step is vitamin K needed?
second step- acts as a cofactor for an enzyme that inserts a second carboxyl group into gamma carbon on glutamic residues
45
What are the 5 roles of thrombin?
1. cleavage of fibrinogen to fibrin 2. activate clotting factors (V,VIII,XI,XIII) 3. activation of platelets 4. activation of endothelial cells 5. binds thrombomodulin and activates Protein C
46
What laboratory measurements evaluates the INTRINSIC and common pathways of coagulation?
activated partial thromboplastin time (APTT) | -clotting time of a mixture of citrated plasma, phospholipid, calcium and an agent to increase contact activation
47
What laboratory measurement evaluates the EXTRINSIC and common pathways of coagulation?
Prothrombin Time | -clotting time of citrated plasma, tissue thromboplastin, and calcium ions.
48
A deficiency in factors VII, X, V, prothrombin and fibrinogen can be seen through what laboratory measurement?
PT
49
T or F- APTT can measure a deficiency in Factors VII and XIII?
False
50
What are 3 basic control mechanisms of regulating clot formations?
1. Blood Flow 2. hepatic clearance of activated factors 3. Plasma Inhibitors
51
What inhibits thrombin by forming a 1:1 complex between arginine residue of itself with a serene residue in active site of thrombin?
antithrombin--also note that it inhibits XIa,Xa, IXa.
52
free thrombin at endothelial cell surface is bound by what? what does it activate?
thrombomodulin- this complex activates protein C and Protein C with S degrades Va and VIIIa AND NO LONGER SUPPORT THROMBIN AND Xa FORMATION
53
What enhances fibrinolysis by degrading endogenous inhibitor of endothelial cell plasminogen activator?
APC (activated protein C) and Protein S
54
What inhibits extrinsic pathway tissue factor/factor VIIa/ factor Xa/ calcium complex?
Tissue factor pathway inhibitor (TFPI)
55
The ability to lyse or dissolve a clot primarily comes from what protein?
Plasmin- From plasminogen produced in liver
56
T-F --plasmin can cleave fibrinogen or fibrin?
True
57
Cleavage of fibrin produces what>
D-dimers
58
What does plasminogen activator T-PA have a high affinity for?
Fibrin
59
What inhibits activation of plasmin?
PAI-1 plasminogen activator inhibitor | - synthesized by endothelial cells, hepatocytes, fibroblasts and platelets
60
What is plasmin activity physiologically regulated by>
alpha 2 antiplasmin--binds lysine binding site on plasmin
61
Normal unperturbed epithelium supports what 3 things?
1. antithrombin inactivation of thrombin (by heparinoids) 2. APC formation (by thrombin/thrombomodulin complex 3. Prostacyclin- inhibit platelet adherence/aggregation
62
Patients with deficiencies in factor VIII or IX have what bleeding disorder?
hemophilia
63
What do patients with deficiency of Protein C or antithrombin have?
increased risk of clotting because missing normal checks of clotting process.

HOS Unit 3 (9 decks)

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