Haemopoiesis Flashcards
most appropriate site for bone marrow examination?
posterior iliac crest
most appropriate technique to assign cell lineage?
..
what is haemopoiesis?
formation of blood cells
3 categories of mature blood cells?
red cells
platelets
white cells
only which category of blood cells have a nucleus?
white cells
categories of white cells?
granulocytes
monocytes
lymphocytes
types of granulocytes?
neutrophils
eosinophils
basophils
function of neutrophils?
phagocytosis/acute inflammation
function of eosinophils?
destroy parasites
modulate hypersensitivity reactions
function of basophils?
modulate hypersensitivity
types of monocytes and their function?
macrophages
modulate immune reactions
phagocytic clearance
regulatory functions
types of lymphocytes?
B cells (humoral immunity - antibodies) T cells (cell mediated immunity, regulatory functions) NK cells (anti-viral/tumour)
haemopoiesis encompasses what processes?
myelopoiesis or granulopoiesis
erythropoiesis
thrombopoiesis
lymphopoiesis
lifespan of RBCs?
120 days
neutrophils lifespan?
7-8 hours
lifespan of platelets?
7-10 days
how many RBCs produced and lost per second?
2.5 million
how many neutrophils produced and lost per second?
1-2 million
how many platelets are produced per second?
1 million
“blast” suffix means?
nucleated precursor cell
erythroblast = RBC precursor
myeloblast = granulocyte precursor??
what are megakaryocytes?
immediate RBC precursor
polychromatic and not nucleated
what are myelocytes?
nucleuated precursor between myeloblast and neutrophil
where do precursor blood cells come from?
haemopoietic progenitor cells
where do progenitor cells and ultimately all haemopoietic cells come from?
haemopoietic stem cells
stem cells > multipotent progenitors > oligolineage progenitors > mature cells
what developmental events occur in haemopoiesis?
self renewal
proliferation (increase in numbers)
differentiation (descendents commit to one or more lineages)
maturation (descendents acquire functional properties and may stop proliferating)
apoptosis (descendents undergo cell death)
- events can overlap
describe activity of more primitive progenitors (eg stem cells) during steady state haemopoiesis (where production equals death)?
cells are quiescent/dormant
what does myeloid terminology refer to?
marrow lineage or marrow malignancy (non-lymphoid)
where do haemopoietic stem cells originate embryonically?
in the mesoderm
when do committed progenitor cells become detectable in the circulation?
week 5
first site of erythroid activity?
yolk sac
stops by week 10
when does erythroid activity begin in the liver?
week 6
when does erythroid activity begin in the bone marrow?
week 16
continues until adulthood within axial skeleton, pelvis and proximal long bones
bone marrow sites of erythroid activity during growth after birth?
activity in tibia and femur reduces by 20-30
mostly in vertebra > sternum > ribs throughout life
describe bone marrow structure
complex organ surrounded by shell of bone with a neurovascular supply
compartments of bone marrow under the microscope?
cellular (haemopoietic cells and non-haemopoietic cells)
connective tissue matrix
vascular elements
what non-haemopoietic cells are found in bone marrow?
adipocytes
fibroblasts
osteoclasts
osteoblasts
describe the bone marrow vasculature
made of nutrient artery and periosteal network
arterioles drain into sinuses (wide venous vessels) which open into larger central sinuses
how are sinuses different to capillaries?
sinuses are larger and have a discontinuous basement membrane
what makes up the bone marrow sinus?
central canal lined by endothelial cells sitting on top of a basement membrane
endothelial cells connected via tight junctions and fenestrations
how are mature blood cells released from bone marrow?
formed blood cells can pass through fenestrations in endothelial cells to enter circulation
release of RBCs is associated with what?
sinusoidal dilation and increased blood flow
where do neutrophils actively migrate towards
the sinusoid
how are megakaryocytes released into circulation?
extend long branching processes called proplatelets into the sinusoidal blood vessels
platelets bud off
red marrow?
haemopoietically active marrow
yellow marrow?
fatty, inactive marrow
which type of marrow increases with age? what does this cause?
yellow
results in reduction in marrow cellularity in older individuals
what is the myeloid:erythroid ratio?
relationship of neutrophils and precursors to proportion of nucleated RBC precursors
ranges from 1.5:1 and 3.3:1
subsequent to change (e.g ratio reversed in haemolysis)
what regulates haemopoiesis?
intrinsic properties of cells
signals from immediate surroundings and periphery (microenvironmental factors)
specific anatomical area (niche) for optimal developmental signals
