Megakaryopoiesis/Thrombocytes Flashcards
Thrombocytes General
small anuclear cell fragments with azurophilic granules
2-4 microns
purple granules
9-12 day lifespan
Thrombocyte range
150-450 x 10^9/L
Thrombocyte maturation
CFU- GEM CFU-MEG megakaryoblast megakaryocyte platelets
Thrombocyte production
in BM, endomitosis = doubling of DNA content
increase in cell size
nuc gains more lobes
Megakaryoblast
10-15 microns
looks like all other blasts
megakaryocyte
nucleus begins to gain more lobes
enlarges as it matures
megakaryocyte
80-150 microns
multilobed (2-16)
abundant cytoplasm
Demarcation Membrane
an internal system of channels is developed as the megakaryocyte develops
platelets are released in groups = proplatelets
Platelet location
2/3 of platelets circulate the bloodstream
1/3 are in the spleen
Megakaryopoiesis regulators
IL-3 and GM-CSF
thrombopoietin (TPO)= increases megakaryopoiesis
produced by liver! kidney, spleen, BM
Platelet structure (4 zones)
peripheral zone
structural zone
organelle zone
membrane systems
Peripheral Zone
2 layers:
outer- fuzzy glycocalyx layer
interior- cytoplasmic membrane (integrity) & gives rise to system of channels
Structural zone
consists of microtubules, cytoskeletal network
structure & support
Organelle zone
contain mitochondria & 4 types of granules
Membrane system
series of conduits/channels leading from platelet surface to its interior
route to release granules
storage site for ionized calcium
