platelets Flashcards
what are four key roles of platelets
- primary haemostasis
- wound healing
- inflammation
- angiogenesis
describe the development of platelets
in bone marrow, stem cells -> megakaryoblast -> megakaryocytes
- located next to BVs in bone marrow
- once DNA replication finished, granules & membranes form
- pro-platelet extend into capillaries, pro-platelets budd off
- convert to pre-platelets –> platelets
what is the most important regulatory factor
thrombopoietin = TPO
what are the four aspects of primary haemostasis
- injury
- initiation
- extension
- stabilisation
describe each stage of primary haemostasis
injury
- endothelial damage => vascular constriction
initiation
- von willebrand factor in blood binds to exposed collagen
- VWB factor binds platelets via platelet receptor (GP 1B-IX-V)
extension
- platelet activated -> exposes integrin -> proteins link between platelets (e.g. fibrinogen)
- granules released recruiting more platelets
stabilisation
- using clotting cascade, forming fibrin
platelet aggregation pathway
- adherence to collagen
- activation of PG synthesis
- thromboxane A2 released
- triggered release of platelet granules
- ADP, fibrinogen
- aggregation
thromboxane A2
- phospholipase releases AA from platelet membrane
- COX and thromboxane synthase form
it decreased platelet cAMP -> lowers Ca2+ and causes granule release
causes of low platelets
decreased production
- viral infection
- drugs
- marrow failure
increased destruction
- immune thrombocytopenia
- DIC
cause of high platelets
increased production
- myeloproliferative neoplasms
define immune thrombocytopenia
body produces autoantibodies
- against platelets, destruction by phagocytosis
- against megakaryocytic reducing production
treatment for immune thrombocytopenia
prednisone = immune suppression steroid
splenectomy = removes organ of platelet destruction
TPO mimetic = stimulates platelet production
