blood cells 3: platelets Flashcards
recall the intravascular life span of platelets and summarise their origin and function
what are platelets?
fragments of cytoplasm of megakaryocytes
how long do platelets survive in circulation?
10 days
how big are platelets?
2-4µm
how many platelets are produced each day?
10^11
how many platelets does each megakaryocyte produce?
4000
what are some important surface proteins?
GPVI (interact with collagen), αIIbβ3 (integrin that interacts with fibrinogen), α2β1 (integrin that interacts with collagen) GP1b (essential for capture by VWF)
what are some other agonists platelets respond to?
thromboxane, thrombin, ADP
what do α-granules in platelets contain?
growth factors, fibrinogen, VWF, cytokines, clotting factors - can be specifically released when platelet is activated
what do dense granules in platelets contain?
ADP, ATP, serotonin, Ca2+, polyphosphates
what happens when the phoshpholipid membrane is activated?
flip-flop’ reaction - negative phospholipids on inner leaflet become exposed on outer surface -> makes platelet highly attractive to clotting factors in blood
why is the platelet cytoskeleton important?
allows for rapid change in shape
what functions do platelets have?
haemostasis & thrombosis, important in development of atherosclerosis + cancer and infection and inflammation
