Haemopoiesis

Question 1

what is haemopoiesis

Answer 1

the formation of blood cells

Question 2

what are the types of white cells

Answer 2

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)

Question 3

do either red cells (erythrocytes) or platelets have nuclei

Answer 3

no

Question 4

what are the components of haemopoiesis

Answer 4

myelopoiesis/ granulopoiesis (granulocytes)
lympopoiesis (WBC)
erythropoiesis (RBC)
thrombopoiesis (platelets)

Question 5

what is the lifespan of a RBC

Answer 5

120 days

Question 6

what is the lifespan of neutrophils

Answer 6

7-8 hours

Question 7

what is the lifespan of platelets

Answer 7

7-10 days

Question 8

what are blasts

Answer 8

nucleated precursor cells (e.g. erythroblast, myeloblasts

Question 9

what are megakaryocytes

Answer 9

platalet precursors, polypoid (resembles polyp)

Question 10

what are reitculocytes

Answer 10

immediate red cell precursors (polychromasia)

Question 11

what are myelocytes

Answer 11

nucleated precursor between neutrophils and blasts

Question 12

where do precursor cells come from

Answer 12

haemopoietic progenitor cells which come from haemopoietic stem cells

Question 13

what cells can self renew

Answer 13

only stem cells, descendants of these unable

Question 14

what are the developmental events of haemopoiesis

Answer 14

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)

Question 15

what are the order of cells in haemopoiesis

Answer 15

stem cells
multipotent progenitors
oligolineage progenitors (myeloid or lymphoid- have committed to a lineage)
mature cells

Question 16

what are most stem cells doing in haemopoiesis

Answer 16

in quiescent/dormant state

Question 17

what is ‘myeloid’

Answer 17

means tissue resembling bone marrow

also is a lineage of cells (not lymphoid- granulocytes and monocytes)

Question 18

where in embryo do haemopoietic stem cells originate

Answer 18

mesoderm

Question 19

where does haemopoiesis happen

Answer 19

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

Question 20

where is bone marrow biopsy done

Answer 20

iliac crest or sternum (in small babies leg can be used)

Question 21

does the bone marrow have a neurovascular supply

Answer 21

yes

Question 22

what are the cellular elements of bone marrow

Answer 22

haemopoietic cells
non haemopoietic cells (adipocytes), fibroblasts, osteoclasts, osteoblasts
connective tissue matrix

Question 23

what is the vasculature of the bone marrow

Answer 23

artery and periosteal network

arterioles drain into into sinuses - wide venous vessels which open into large central sinuses

Question 24

how are the sinuses in bone marrow different from capillaries

Answer 24

are larger and have a discontinuous basement membrane (fenestrations between endothelial cells)

Question 25

how are mature cells released from bone marrow

Answer 25

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

Question 26

what is red and yellow bone marrow

Answer 26

red= haemopoietically active

yellow- fatty inactive (increases with age= reduced marrow cellularity)

Question 27

what is the myeloid: erythroid ratio:

Answer 27

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

Question 28

what regulates haemopoiesis

Answer 28

intrinsic properties of cells 
microenvironmental factors (signal from immediate surroundings and periphery) 
specific anatomical area (niche) for developmental signals

Question 29

what ‘nurses’ macrophages in haemopoiesis

Answer 29

erythroid islands

Question 30

what regulants neutrophil precursor maturation

Answer 30

G-CSF (granulocyte-colony stimulating factor)

Question 31

what regulates the growth and development of megakaryocyte from their precursors

Answer 31

thrombopoietin

Question 32

what is a ‘niche’

Answer 32

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

Question 33

how do you assess haemopoiesis

Answer 33

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)

Question 34

which cell stains red

Answer 34

eosinophils

Question 35

what are you hoping to aspirate in bone marrow biopsy

Answer 35

pre cursor cells

Question 36

what is immunophenotyping

Answer 36

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)

Question 37

what is the most appropriate test to assign cell lineage

Answer 37

immunophenotyping