Haemopoiesis Flashcards
what is haemopoiesis
the formation of blood cells
what are the types of white cells
granulocytes:
- neutrophils: phagocytosis/ acute inflammation
- eosinophils: destroy parasites, hypersensitivity
- basophils: hypersensitivity
monocytes:
- macrophage precursors
- phagocytes
- regulatory function
lymphocytes:
- B cells: humoral immunity (antibodies)
- T cells (cell mediated immunity, regulatory functions)
- NK cells (anti viral/ tumour)
do either red cells (erythrocytes) or platelets have nuclei
no
what are the components of haemopoiesis
myelopoiesis/ granulopoiesis (granulocytes)
lympopoiesis (WBC)
erythropoiesis (RBC)
thrombopoiesis (platelets)
what is the lifespan of a RBC
120 days
what is the lifespan of neutrophils
7-8 hours
what is the lifespan of platelets
7-10 days
what are blasts
nucleated precursor cells (e.g. erythroblast, myeloblasts
what are megakaryocytes
platalet precursors, polypoid (resembles polyp)
what are reitculocytes
immediate red cell precursors (polychromasia)
what are myelocytes
nucleated precursor between neutrophils and blasts
where do precursor cells come from
haemopoietic progenitor cells which come from haemopoietic stem cells
what cells can self renew
only stem cells, descendants of these unable
what are the developmental events of haemopoiesis
self renewal (stem cells)
proliferation (increase in numbers)
differentiation (descendent commit to one or more lineages)
maturation (descendants acquire functional properties and may stop proliferating)
apoptosis (descendants undergo cell death)
what are the order of cells in haemopoiesis
stem cells
multipotent progenitors
oligolineage progenitors (myeloid or lymphoid- have committed to a lineage)
mature cells
what are most stem cells doing in haemopoiesis
in quiescent/dormant state
what is ‘myeloid’
means tissue resembling bone marrow
also is a lineage of cells (not lymphoid- granulocytes and monocytes)
where in embryo do haemopoietic stem cells originate
mesoderm
where does haemopoiesis happen
Yolk sac, the first site of erythroid activity, stops by week 10
Liver starts by week 6
spleen 2-7 months (fetus)
Bone marrow by week 16
adults- axial skeleton, pelvis and proximal long bones
where is bone marrow biopsy done
iliac crest or sternum (in small babies leg can be used)
does the bone marrow have a neurovascular supply
yes
what are the cellular elements of bone marrow
haemopoietic cells
non haemopoietic cells (adipocytes), fibroblasts, osteoclasts, osteoblasts
connective tissue matrix
what is the vasculature of the bone marrow
artery and periosteal network
arterioles drain into into sinuses - wide venous vessels which open into large central sinuses
how are the sinuses in bone marrow different from capillaries
are larger and have a discontinuous basement membrane (fenestrations between endothelial cells)
how are mature cells released from bone marrow
pass through fenestrations in endothelial cells
release of red cells is associated with sinusoidal dilatation and increased blood flow
neutrophils actively migrate to the sinusoid
megakaryocytes extend long branching proplatelets into the sinusoidal blood vessels
what is red and yellow bone marrow
red= haemopoietically active
yellow- fatty inactive (increases with age= reduced marrow cellularity)
what is the myeloid: erythroid ratio:
relation of neutrophils and precursors to proportion of nucleated red cell precursors
usually 1.5:1 to 3.3:1 but this reverses in haemolysis to compensate
what regulates haemopoiesis
intrinsic properties of cells microenvironmental factors (signal from immediate surroundings and periphery) specific anatomical area (niche) for developmental signals
what ‘nurses’ macrophages in haemopoiesis
erythroid islands
what regulants neutrophil precursor maturation
G-CSF (granulocyte-colony stimulating factor)
what regulates the growth and development of megakaryocyte from their precursors
thrombopoietin
what is a ‘niche’
an anatomical site that is occupied by stem cells provides signals (via near by arterioles/ sinusoids) signals (cytokines) for expansion, differentiation and dormancy
niches can be altered in diseased states or with therapy
how do you assess haemopoiesis
non lymphoid mature cells:
- FBC, cell indices, morphology (blood film)
- bone marrow examination
lymphoid mature cells: -immunophenotyping (expression of antigens indicating linage and stage of development)
progenitor/ stem cells: -immunophenotyping -clonogenic assays -animal models (are morphologically indistinguishable cells)
which cell stains red
eosinophils
what are you hoping to aspirate in bone marrow biopsy
pre cursor cells
what is immunophenotyping
identifies patterns of protein (antigen) expression unique to a cell lineage
uses antibodies specific to different antigens and fluorescent dyes which are detected by flow cytometry (lasers)
what is the most appropriate test to assign cell lineage
immunophenotyping
