Cheatography
https://cheatography.com
- Platelets (functions & structure)
- Hemostasis
- Coagulation (factors & pathways)
- Laboratory Evaluation
This is a draft cheat sheet. It is a work in progress and is not finished yet.
BLOOD VESSEL
CONNECTIVE TISSUE: |
Fibroblasts |
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Smooth Muscle Cells |
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These cells secrete COLLAGEN - a negatively charged substance; platelet agonist |
BASEMENT MEMBRANE: |
Collagen-rich (from CT) |
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Serves as support of endothelial lining |
ENDOTHELIAL LINING: |
Secretes Heparan Sulfate |
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- an natural anticoagulant to keep blood flowing without turbulence in intact subendothelium |
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- heparan sulfate is inactivated by B-thromboglobulin and Platelet Factor 4 for hemostasis to proceed |
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- Zeta potential is also responsible for keeping platelets from touching the subendothelium |
Zeta Potential: |
Platelets: Phospholipids (phosphotidylethanolamine) |
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Endothelial Lining: Collagen (from CT) |
- A platelet is a negatively charged cell (from phospholipids) that can be activated by negatively-charged substances called PLATELET AGONISTS
PLATELET FUNCTIONS
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1. ADHESION: Adhered Platelets: single-layer of platelets
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Collagen-stimulated adhesion
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Platelet > GP Ib/IX > vWF > Collagen
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(Platelets have a GP Ib/IX binding site on their membrane that von Willebrand Factor attaches to, to form a bridge between platelets and collagen — found on the subendothelium)
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2. SECRETION: Adhered platelets secrete DENSE GRANULES
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ADP (from dense granules) recruit & activate surrounding inert platelets
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(Adhered platelets are REactivated by thromboxane A2 to secrete granules thru OCS)
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3. AGGREGATION: ADP-stimulated Platelets expose GP IIb/IIIa
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Fibrinogen attaches to GP IIb/IIIa
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Primary Platelet Plug is formed (loose clot)
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(Fibrinogen bridges the GP IIb/IIIa binding sites of each platelet to create long spiny projections that indicate activation, and lead to aggregation)
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- Platelet functions always have to be enumerated in order
- The 3 functions comprise the events of PRIMARY HEMOSTASIS, meaning its output is a primary platelet plug
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PLATELET AGONISTS
ARACHIDONIC ACID |
- strongest platelet agonist |
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without this, secretion cannot happen = no ADP-stimulated platelets, and no primary platelet plug formation |
THROMBOXANE A2 |
- stimulates secretion |
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it reactivates the adhered platelets to secrete granules |
ADENOSINE DIPHOSPHATE |
- stimulates aggregation |
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from dense granules; causes the aggregation of platelets to form a primary platelet plug = ADP-stimulated Platelets |
THROMBIN (agonist & Factor IIa) |
- most important protease enzyme |
COLLAGEN |
- electronegativity in connective tissue |
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*source of negative charge in connective tissue -> epithelial lining |
EPINEPHERINE |
THROMBOXANE A2 AND ARACHIDONIC ACID PATHWAY
This pathway shows what happens upon injury to blood vessel
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