antiplatelet drugs Flashcards
what are the steps to the formation of platelets?
haemocytoblast-> myeloid stem cell-> megakaryoblast-> promegakaryocyte-> megakaryocyte-> platelets
what are the general properties of platelets?
theyre very small, theres lots of them, 250,000-500,000 per cubic vasculature
they survive from 7-10 days
theyre formed in the bone marrow
what does thrombopoietin?
it regulates platelet production
what are the physiological properties of platelets?
o Adhesion – ability to stick to the foreign and damaged surface
o Aggregation – ability to form a clump (cork)
o Agglutination – pasting of thrombocytes one with another
what is the first response to vascular inhury?
vasoconstriction
compression of the vessel by the blood escaping
injury ‘chemicals’ are released by injured cells
reflexes from adjacent pain receprors
what are the steps involved in the formation of a platelet plug?
- platelets attach to damaged vessel wall to plug it
- platelets produce thromboxane A2
- serotonin and histamine release enhances vascular contraction
- ADP - attracts and stimulates platelets at site
prostacyclin - inhibits aggregation at other sites - a sharply cut vessel undergoes less spasm i.e. it bleeds for longer and a toren vessel
what happens in platelet plug formation?
- the platelets aggregate to control the blood loss from the vessel
- if damage is small, then the formation of the plug stops the bleeding
- platelets undergo dynamic change in appearance and begin the process of adhesion and activation due to exposure to collagena nd other foregin substances
what receptors are improtant in the formation of platelet plug formation with collagen?
integrin receptors are important in regards to collagen presence
what foregin substances cause the platelet to undergo dynmic change in appearance?
antigen-antibody complexes, thrombin, proteolytic enzymes, endotoxins, and viruses
what occurs in adhesion of platelets?
the platelets swell and become sticky and adhere to collagen fibril on the basement membrane, it requires von williebrand factor (vWF) adhere to collagen fibrils on the basement membrane
what do the granules released by activated platelets contain?
containing vWF, factor V, PDGF, heparin-neutralizing protein, and ADP (attracts other platelets)
what happens in secondary homeostasis
what happens in primary homeostasis
what does factor X do?
what happens in the intrinsic pathway?
it occurs within the damaged…