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Hemostasis Flashcards

(44 cards)

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1
Q

What is hemostasis

A

Mechanism for cessation of blood loss

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2
Q

Where does the interaction of plasma proteins take place?

A

Platelet Surface

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3
Q

What is the first response to initial injury?

A

Arteriolar vasoconstriction

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4
Q

What is involved in Primary Hemostasis?

A

Adhesion, Aggregation, Secretion, Clot formation and retraction, Support of plasma coagulation and support of endothelium

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5
Q

What is adhesion?

A

Attachment of platelets on surface of site of injury

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6
Q

What is exposed to indicate injury?

A

Collagen on surface of endothelium

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7
Q

What is required for platelet adhesion?

A

Von Willebrand factor and glycoprotein IB (receptor found on platelet)

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8
Q

Where is Von Willebrand factor found and stored?

A

In Endothelial cells

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9
Q

What is the function of Von Willebrand factor?

A
  1. Binds to platelet receptor (Gp IB)
  2. Binds to collagen
  3. Binds and stabilizes Factor VIII
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10
Q

What is platelet aggregation?

A

Recruitment of additional platelets to form clumps

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11
Q

What is needed for platelet aggregation?

A

Binding of Fibrinogen to glycoprotein IIb-IIIa

Shape change takes place to increase surface area

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12
Q

What is the role of fibrinogen?

A

Causes platelets to aggregate

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13
Q

What causes shape changes in platelets?

A

ADP receptors present on platelet surface

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14
Q

What is platelet secretion?

A

The release of granular contents and prostaglandin metabolites from activated platelets

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15
Q

What do dense granules contain?

A

ATP, ADP, Calcium, and serotonin

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16
Q

What do alpha granules contain?

A

Coagulation factors, growth modulators, adhesive proteins

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17
Q

What are types of coagulation factors?

A

Factor V, Factor XIII, Factor VIII, Fibrinogen, vWf

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18
Q

What are some growth modulators?

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A

Platelet factor 4, platelet derived growth factor, epidermal growth factor, thrombospondin, TFG beta

19
Q

What are some adhesive proteins?

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A

Fibronectin, Thrombospondin, Fibrinogen

20
Q

How are alpha and dense granule contents released?

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A

Through the open canalicular system in platelets

21
Q

What does release of granule contents do?

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A

Vasoconstriction (serotonin)
Modulation of growth of vessel walls (platelet-derived growth factors)
Cell adhesion and fluid phase coagulation (clotting factors)

22
Q

What is involved in platelet activation?

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A

Platelet stimulation activates Phospholipase A2. Phospholipase A2 generates Arachidonic Acid.
Arachidonic acid is converted to cyclic-endoperoxide.
Cyclic endoperoxide makes Thromboxane A2

23
Q

What is involved in the fluid phase coagulation?

Study These Flashcards
A

The stabilization of the clot.
Platelets have actin and myosin and organize in the filipodia.
Filipodia binds to fibrin strands and contraction draws them together to tighten the clot

24
Q

Summarize Fluid Phase Coagulation

Study These Flashcards
A

Vessel injury leads to activation of coagulation cascade, followed by thrombin generation, finally leading to fibrin generation for clot formation

25
What are primary inhibitors of platelet aggregation?
Prostacyclin (made my endothelial cells) | Nitric Oxide causes vasodilation
26
Most clotting factors are ________
Serine Protease
27
Where are most enzymes made?
The liver
28
What is the final product of the fluid phase coagulation?
Thrombin acts on Fibrinogen to make Fibrin
29
What does Fibrin do?
It stabilizes Factor XIII by forming cross links with it (calcium needed)
30
How is fibrinogen converted to fibrin?
Thrombin acts on Fibrinogen and clips off the fibrinopeptides from fibrinogen making a fibrin monomer. These monomers come together to polymerize but they are unstable. Thrombin also acts to convert XIII to XIIIA. Fibrin polymers + Factor XIIIA make a stable form insoluble fibrin
31
Describe the first part of the coagulation cascade.
Tissue factor binds to Factor VII and activates it to Factor VIIA. Factor VIIA binds to Factor IX activating it to Factor IXA Factor VIIA binds to Factor X activating it to Factor XA Factor XA changes prothrombin to thrombin
32
What does Thrombin do (initially)?
Thrombin produced in small amounts at the beginning of the coagulation cascade goes back to the beginning of the entire pathway to active more cofactors ad potentiates the entire process. Factor V to VA and Factor VIII to VIIIA
33
Once large amounts of thrombin are made, what happens next?
Complexes are made between Factor VA and Factor XA. Factor VIIIA and Factor IXA. This revs up the entire process to produce substantial amounts of thrombin which can now convert fibrinogen to fibrin in substantial amounts.
34
What are the two pathways for in-vitro pathways? | What do they work on together?
``` Intrinsic - Partial Thrombin Time Extrinsic - Prothrombin Time Both work to activate Factor X to Factor XA Factor Xa + Prothrombin makes thrombin Thrombin + Fibrinogen makes Fibrin ```
35
What are the Vitamin K dependent proteins?
Prothrombin, Factor VII, Factor IX, Factor X, Protein C and Protein S
36
What are the steps involved in synthesis of vit. K dependent proteins?
1. Polypeptide is formed in hepatic ribosomes 2. Vit. K acts as cofactor to insert carboxyl group into glutamic acid residues, which creates a gamma-carboxyglutamic acid essentially making clotting factors
37
What are control mechanisms for fibrin formation?
Blood flow (circulating blood away from areas of fibrin) Hepatic clearance of activated coagulation factors Plasma inhibitors
38
What is antithrombin
It inhibits thrombin by forming a complex between arginine residue on antithrombin and serine active site of thrombin
39
What is Protein C and Protein S?
Protein S and active protein C (APC) work to degrade factor Va and VIIIa so they no longer support thrombin and Xa formation. APC and Protein S also enhance fibrionolysis
40
What is fibrinolysis?
Lysis of a blood clot. | Plasminogen is cleaved to form plasmin
41
How is Protein C converted to APC?
Prothrombin + Thrombin forms a thrombomodulin complex. Protein C + thrombomodulin complex forms APC. Protein S + Factors Va and VIIIa converts these to their inactive forms
42
What is plasmin?
Plasmin degrades into fibrin or fibrinogen which eventually leads to fibrin degradation products. Plasminogen + Tissue Plasminogen Activator gives Plasmin. Plasmin +fibrin gives fibrin degradation products
43
What is a clot-busting drug?
TPA (Tissue Plasminogen Activator)
44
Where does aspirin act in the clot formation cascade?
Platelet Activation. | Works to block arachidonic acid to be converted to cyclic-endoperoxide which eventually forms thromboxane A2

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