Intro to Hemostasis
Terms
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- Define hemostasis
- the balance between clotting and lysing.
- Define the hemostasis mechanism
- the property of the circulatory system whereby fluid is maintained within the blood vessels.
- How do the vessels/plts/coag factors interact? (3 things)
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1. Vessels have FAST graded response.
2. Platelets form the plug
3. Coag/fibrinolytic factors hold it all together. - what 3 additional systems interact w/ coag factors?
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1. Kinin system
2. Serine protease inhibitors
3. Complement system - What composes the kinin system and what is the most important one?
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-Small peptides.
-Bradykinin is most important. - What are the 2 main actions of bradykinin?
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-Vascular permeability
-Pain mediator - What activates bradykinin?
- Factor 2
- What ARE the serine protease inhibitors?
- Natural anticoagulants that dampen the coag response.
- Name 4 serpins.
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1. AT-III
2. Heparin cofactor II
3. alpha-2-trypsin
4. a2-macroglobulin - How does the complement system interact w/ the coag cascade?
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-Interface between the 2 systems
-Mediates immune/allergic response. - What activates the complement system?
- Plasma
- What are the 2 types of properties of the vasculature that are involved with coagulation?
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1. Procoagulant
2. Anticoagulant - What are the procoagulant PROPERTIES of the vasculature? (3)
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1. Vasoconstriction to divert blood flow in capillaries.
2. Initiates contact activation.
3. Endothelial cells -> vWF - What are the anticoagulant PROPERTIES of the vasculature? (3)
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1. Thrombomodulin activates protein C.
2. Tissue factor pathway
3. Vessels have a smooth surface for blood flow. - The 3 areas of interaction btwn the Vasculature/hemostasis are:
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1. Endothelial cell lining
2. Subendothelium
3. Vasoconstriction - How does the vessel endothelial cell lining affect hemostasis? (3 properties)
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1. Prostacylin (PGI2)
2. Tissue fluid
3. ADP - What are the 2 actions of Prostacylin from the EC lining?
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1. Inhibition - disaggregates platelets and prevents clot.
2. Vasodilation - opens blood vessel, preventing - How does tissue fluid from the EC lining interact w/ clotting?
- Contains coagulant factors, will initiate the process.
- How does ADP from EC lining affect clotting?
- It inhibits the calcium receptor, thus increases cytoplasmic Calcium.
- What property of the SUBendothelium affects clotting?
- Its collagen attracts platelets, thus helping with coagulation.
- What causes vasoconstriction?
- Nerve reflex - thus it's instantaneous.
- How does vasoconstriction enhance platelets?
- It releases TxA2, thromboxane.
- What is Thromboxane?
- a Potent Platelet Aggregator and antagonist of prostacyclin.
- What is thromboplastin?
- Factor present in tissues that aids Fx VIIa in activating Fx X via the extrinsic cascade.
- What 6 products from vasoconstriction affect coag?
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1. TxA2 (Thromboxane) PRO
2. ADPase - Anti
3. ADP - PRO
4. vWF - PRO
5. Plasminogen activator Anti
6. Thromboplastin PRO - What stage of hemostasis do platelets affect?
- PRIMARY
- What are the 5 actions of platelets in coagulation?
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1. Adhere to subendothel via vWF
2. Primary aggregation (reversible)
3. Scndry aggr (nonreversible)
4. "Release reactions"
5. Platelet surface - What 3 substances do platelets release in their granules?
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1. Thromboxane A2
2. SErotonin
3. ADP - again, what is TxA2's action?
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-Potent platelet aggregator
-Antagonist of prostacyclin. - What does Seretonin do?
- Aids in aggregation
- What is the role of ADP when released from platelets?
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-Released from dense bodies
-Recruit more platelets from the storage pool. - What is on the SURFACE of platelets?
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1. Negative charge
2. Heparin sulfate
3. PGI2 -
What is the activator of the:
-Intrinsic pathway
-Extrinsic pathway -
Intrinsic: EXposed collagen
Extrinsic: Tissue thromboplastin - What factor is Thrombin?
- Factor IIa
- What are the 6 actions of thrombin (2a)?
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1. Activates plt aggregation
2. Activ. INTRINSIC by Fx XII
3. Converts Fibrinogen->fibrin
4. Activates Fx XIII to stabilize the fibrin clot.
5. Activates Protein C
6. Activates V->Va/VIII->VIIIa - What is the purpose of Protein C?
- To keep the clotting reaction confined to an immediate area.
- What is the purpose of fibrinolysis?
- To return the vasculature to its normal, smooth state.