Haemopoeisis Flashcards
What is haemopoeisis
formation of blood cells
what is erythropoeisis
formation of RBCs
what is myelopoeisis
formation of white blood cells - granulocytes and monocytes
what is lymphopoeisis
formation of lymphocytes
what is thrombopoeisis
formation of platelets
in the steady state, cell loss is balanced by cell production, true or false
true
what is the normal average lifespan of RBCs
120 days
what is the normal average lifespan of neutrophils
7-8 hours
what is the normal average lifespan of platelets
7-10 days
what are “blasts”
give examples
nucleated precursor cells
erythroblasts
myeloblasts
what are megakaryocytes
polyploid platelet precursor cells
what are reticulocytes
immediate mature RBC precursor
polychromatic
what are myelocytes
nucleated precursor between neutrophils and “blasts”
stem cells are dormant/active during steady state haemopoeisis
dormant
what are the steps in the haemopoeitic tree
Self renewal Proliferation Differentiation/lineage commitment Maturation Apoptosis
from which germ layer do haemopoeitic stem cells arise
mesoderm
where is the first site of haemopoeisis in a foetus
yolk sac
stops at week 10
in the foetus, where is another site of haemopoeisis at week 6
liver
at week 16 in the foetus, what is another site of haemopoeisis
bone marrow
where is haemopoeisis in an adult
in the bone marrow of the axial skeleton, pelvis and proximal long bones
where would you take a bone marrow biopsy from in:
adults
children
adults - posterior iliac crest
children - proximal anterior tibia
what is bone marrow
complex organ with a shell of bone and a neurovascular supply
what are the 3 main compartments of bone marrow
cellular
vascular
connective tissue stroma
what are the cellular components of bone marrow
haemopoeitic
non-haemopoeitic: adipose, osteoblasts, osteoclasts, fibroblasts
describe the vasculature of bone marrow
network of thin walled fenestrated sinusoidal vessels
it is supplied by a nutrient artery
what is the difference between venous sinuses and capillaries
venous sinuses are larger and have a discontinuous basement membrane (sinusoidal)
what are sinusoids and where can you find them
irregular blood filled spaces with extra large fenestrations to allow passage of proteins/blood cells
endothelial cells do not overlap each other
found in bone marrow, liver and spleen
describe the process of RBC leaving the bone marrow
they leave through sinusoids (fenestrations in endothelial cells) to enter circulation
this is associated with sinusoidal dilatation and increased blood flow
neutrophils actively migrate to the sinusoid
megakaryocytes extend branches called proplatelets into sinusoidal blood vessels
what is the difference between red and yellow bone marrow
red = haemopoeitically active yellow = fatty, inactive, increases with age
what is the myeloid:erythrocyte ratio
(M:E ratio)
what is the benefit and what is the normal ratio
compares number of nucleated precursors of myeloid and erythroid cells
it allows us to look at the production of these
normally M:E is 1.5-3.3:1
why can the M:E ratio be reversed
in haemolysis
as the bone marrow is trying to make more red cells to compensate
how is haemopoeisis regulated
Intrinsic properties of the cell
Microenvironmental factors/signals
Anatomical location “niche” for optimal developmental signals
where are macrophages nursed in haemopoeisis
erythrocyte islands
what is G-CSF and what is its function
Granulocyte colony stimulating factor
regulates neutrophil precursor
which hormone regulates growth of megakaryocytes from their precursor
thrombopoeitin
where is the haemopoeitic stem cell niche located and how can it be affected
niche is located around vasculature to provide access to cytokines
can be altered by disease or treatments
what investigations are done for mature non-lymphoid cells
FBC
cell indices
blood film
bone marrow aspiration
what investigation is done for mature lymphoid cells
immunophenotyping
what is immunophenotyping
study of antigen expression unique to a lineage using specific antibodies
how is immunohistochemistry measured
flow cytometry
