Haematopoiesis Flashcards
RBCs:
1. no. in body?
2. lifespan?
3. how many per day?
- 20-30 trillion
120 days
4000million per day
3 reasons RBC count might need to change
- sudden need e.g. haemorrage, injury
- temp need e.g. at higher latitudes
- chronic need e.g. compensating for disease like Hb disorders
how many WBCs per day made
10,000 milion per day
how many platelets/ day made
400,000 million (dont last long)
too many platelets can cause what
gangrene, blocked vessels
OG stem cell
multipotent haematopoietic stem cell
partially differentiated cuz only blood cells
2 ways stem cells can differentiate
new precursors to blood cells
self renew to maintain stem cell number
why is proliferating and differentiating pool of stem cells so importnat
control rate of production
how many mature cells does a stem cell make
500,000 (19 cycles of proliferation)
what 2 cytokines affect early stem cell
- stem cell factor
- interleukin 3
what 3 cytokines act on cells further down
- thrombopoietin
- erythropoietin
- GM-CSF
what cytokines control function of cells (ie act on more mature cells to specialise them)
G-CSF
M-CSF
for a steady state, how should initial stem cells divide
- one should differentiate/proliferate
- other should self replicate
(all depends on needs of body)
Stem cell niche
- cytokines
- adhesive proteins
- supporting stromal cells
process from myeloid precursor to neutrophil
common myeloid precursor
myeloid blast cell
promyelocyte
myelocyte
metamyelocyte
neutrophil
chance of cell death in haematopoiesis and reason
40%
number of cells produced can be rapidly increased
how come proliferating cells are protected form forming cnacer
cant self renew
how does EPO work
responds to O2 levels,
= acts on RBC precursors, enhances their survival
= may inc total number of divisions made
where is O2 level detected
in kidney, where EPO will be secreted from
what does G-CSF control
neutrophil number and function
how does G-CSF work
inc survival of precursors
inc maturation rate and granule formation = inc function
ways G-CSF increases neutrophil function
inc their mobility
inc number of granuels
inc ability to stick to bacteria
what does G-CSF respond
normally enough for baseline number of neutrophils
but if infection then will inc
what does TPO affect
thrombopoietin = platelet production
what cells does TPO act on
megakaryocytes
enhances survival of its precursors
where is TPO made and how controlled
- in liver
- mature platelts bind and destroy TPO
other than for TPO and EPO, what is major source of growth factors
stromal cells
