platelets Flashcards
Anucleate cells derived from megakaryocytes
in the bone marrow
platelets
platelets:
- production
- nl count
- circulation lifespan
- production: GM-CSF, IL-3, IL-6, TPO
- nl count: 150,000- 400,000
- circulate in the inactive state for 7-10 days
Alpha granules:
- fibrinogen
- thrombospondin
- vWF
- Factor V
- Platelet factor 4
- Beta thromboglobulin
- PDGF (platlet derived growth factor)
- P-selectin
- fibrinogen- aggregation
- thrombospondin- aggregation
- vWF- adhesion/aggregation
- Factor V- fibrin clot
- Platelet factor 4- heparin antagonist–promotes fibrin clot
- Beta thromboglobulin- recruits fibroblasts
- PDGF (platlet derived growth factor)- recruits fibroblasts
- P-selectin- adhesion of activated platelets to phagocytes
dense granules
- ADP and ATP
- Serotonin (5-HT)
- calcium
- ADP and ATP- platelet activation and recruitment
- Serotonin (5-HT)- vasoconstriction
- calcium- cofactors for factors forming fibrin clot
lysosomes
are granules that contain hydrolytic enzymes which phagocytose debris
Glycoprotein (GP) Ib (Ib/IX/V):
vWF receptor
Glycoprotein Ia/IIa:
collagen receptor
Glycoprotein IIb/IIIa:
fibrinogen receptor
procoagulant activity (2)
- thrombin receptor
2. phospholipids
P-selectin (activated platelets only)
leucocyte adhesion
bound to the collagen in the subendothelium of the damaged vessel wall, binds to platelets via GPIb complex, acting as a bridge
vWF
in the damaged vessel wall can bind to the platelet via GPIa/IIa
collagen
involved in adhesion for platelets (2)
- vWF
2. collagen
activating agents in platelets (6)
- thromboxane A2
- thrombin
- epinephrine
- ADP
- collagen
- arachidoinic acid
three actions of the activating agents
- enhances cell interaction (GPIIb/IIIa)
- induces platelet shape change and secretion
- phspholipids on plasma membrane activate clotting on the external surface
shape change with platelets
change from discoid to spherical- develop long pseudopods
where do the granules release their contents?
into the canalicular system
in aggregation the platelet-platelet interaction mediated by ______ and promoted by thombospondin
GPIIb/IIIa with fibrinogen
what does ADP and thromboxane A2 do in aggregation?
swelling, membrane adhere and further release reaction