platelet activation Flashcards
(18 cards)
where are platelet derived from ?
megakaryocytes
what is the production of platelets regulated by ?
TPO thrombopoeitin
what are the three steps associated with platelet action ?
adhesion
aggregation
secretion
where is VWF made ?
by endothelial cells and megakaryocytes,
where is VWF stored ?
1- stored in weibel palade bodies in the endothelial cells
2- stored in alpha granules in the megakaryocytes
what is the trigger for the release of VWF ?
released with vascular injury
activated platelets degranulate
endothelial cells release the vWF
what are the roles of vWF in hemostasis ?
1- carrier protein for factor 8
2- binds platelets together
2- allows for platelet aggregation
what allows for the activation of factor 8 ?
thrombin( factor 2a) cleaves factor 8 to activate it
what are the membrane glycoproteins ?
glycoproteins on the surface of platwlets that allow aggregation
need GPIb , GPIIb/IIIa
what are the different glycoproteins associated with each stage of platelet action ?
adhesion : GP 1b
aggregation : GP IIb/IIIa
what is the function of platelet factor 4 ?
released from alpha granules , bind to endothelial cells
what is the assocition between platelet factor 4 and HIT ?
platelet 4 factor and injected heparin especially unfractionated form a complex together which is then identified as a foreign body , attacked by the immune system with formation of IgG , which in turn activated more platelets and the patient enters a hypercoagubale state
thrombocytopenia associated
what is the diagnostic test for heparin induced thrombocytopenia ?
serotonin release assay
what is the clinical tie in with ADP and platelet activation ?
the release of ADP is associated with decreased cAMP formation which allows for platelet activation and more sticking
we give phosphodiestrase inhibitors in order to increase cAMP levels and block platelet activation
what are examples of ADP receptor blockers and what do they do ?
drugs like clopidogrel which inhibit platelet activity
what is the function of thromboxane A2 and what is their clinical tie in ?
they also activate platlets and they are the basis for aspirin therapy
how does aspirin work ?
inhibits COX , which decreases thromboxane A2 and decreases platelet activation
what does the bleeding time test ?
platelet function keda men bara
