WEEK 1: Haematopoiesis and Anaemias Flashcards
what’s the main function of rbcs?
transport O2 and CO2
what’s the main function of neutrophils?
phagocytose and destroy invading bacteria
what’s the main function of eosinophils?
destroy larger parasites and modulate allergic inflammatory responses
what’s the main function of basophils?
release histamine
what’s the main function of monocytes?
become tissue macrophages, which phagocytose and digest invading microorganisms and foreign bodies as well as damaged senescent cells
what’s the main function of B cells?
making antibodies
what’s the main function of T cells?
kill virus infected cells and regulate activities of other leucocytes
what’s the main function of NK cells?
kill virus infected cells and some tumour cells
what’s the main function of platelets?
initiate blood clotting
what does totipotent mean?
form all cells including extraembryonic and placental cells
what does pluripotent mean?
give rise to all cell types
what does multipotent mean?
give rise to more than one cell type but limited, eg all blood cells have common ancestral cell - multipotent stem cell
what is the stem cell theory of haematopoiesis?
- All cells derived from a pool of stem cells that are self-renewing
- Pluripotential & multipotential stem cells give rise to committed stem cells for each cell line
- Committed stem cells have receptors for specific growth factors
- Respond to stimulation by division & maturation (precursor cell stages) into end-stage cells
what are the characteristics of hematopoietic stem cells?
- Stem cells defined as capable of both self
renewal and multi-lineage differentiation - HSC are multi-potent stem cells that occur at a
frequency of 1:5000 in bone marrow - HSC can be defined by:
Function: the capacity to give rise to non-self renewing populations that generate multiple terminally-differentiated cell types
explain the development of blood cells in a fetus.
3 wk : formation of blood islands from yolk sac
6 wk : liver becomes hematopoietic organ
6-8 wk : spleen (until 8th month)
~20wk : bone marrow (life-long)
what is a stem cell niche?
a specific site (microenvironment) in adult tissues where stem cells reside and undergo renewal and differentiation
which 2 distinct hematopoietic niches does bone marrow harbour and where?
(1) Osteoblastic niche at the endosteal surface
(2) Vascular niche involving sinusoidal blood vessels
what function does the osteoblastic niche have to help balance self-renewal with differentiation?
Osteoblastic niche maintains quiescence and harbours the Long Term-HSC
what function does the vascular niche have to help balance self-renewal with differentiation?
Vascular niche supports proliferation, differentiation and mobilization (transendothelial migration) of Short Term-HSC to the blood stream in response to physiological demands and act as back up outside the BM for HSC during times of BM stress
what is erythropoiesis ?
the generation of red blood cells
what are the stages of erythropoiesis?
Proerythroblast
Erythroblast
Normoblast
Reticulocyte
Erythrocyte (fully mature red blood cell)
how long is the erythropoiesis process?
5-7 days
what is a proerythroblast?
it is the first committed to rbc