Haemopoiesis Flashcards
What is haemopoiesis
The formation of blood cells
Name the three types of mature blood cells
Red cells (erythrocytes)
Platelets (thrombocytes)
White cells (leukocytes)
State the two blood cells that don’t have a nucleus
RBCs (erythrocytes)
Platelets (thrombocytes)
Name the three sub types of leukocytes
Granulocytes
Monocytes/macrophages
Lymphocytes
Name the three white cell granulocytes and state their function
Neutrophils (phagocytosis/acute inflammation)
Eosinophils (parasites, hypersensitivity)
Basophils (hypersensitivity)
State the 2 main function of monocytes/macrophages
They modulate immune reactions
They are involved in Phagocytic clearance
Name the three types of lymphocytes and state their function
B cells (humoral immunity)
T cells (cell-mediated immunity)
NK cells (anti-viral/tumour)
Red cell lifespan
120 days
Neutrophil lifespan
7-8 hours
Platelets lifespan
7-10 days
If a cells name ends in -blast, what does this mean?
It is a nucleated precursor cell
State the name for RBC, platelet & neutrophil precursors
Erythrocyte - (erythroblast & then) Reticulocyte
Platelet - Megakaryocyte
Neutrophil - (myeloblast & then) Myelocyte
What can form from a myeloid precursor cell
Erythrocytes
Thrombocytes
Granulocytes (neutrophils/basophils/eosinophils)
Monocytes/macrophages
(+ dendritic cells)
What can form from a lymphoid precursor cell
Lymphocytes
- T cells
- B cells/ plasma cells
- NK cells
(+ Dendritic cells)
What is self renewal & what cell type has this property
Every time a stem cell divides it produces one cell that is exactly like its self (self renewal) & one cell that is not
HSC can self renew, progenitor cells cant
Proliferation vs differentiation vs maturation
- Proliferation - Increase in numbers
- Differentiation - Descendants commit to one or more lineages
- Maturation - Descendants acquire functional properties & may stop proliferating
Haemopoietic stem cell vs progenitor cells vs precursor cells
- HSC - can self renew & differentiate into any blood cell type
- Progenitor cell type - can differentiate into multiple blood cell types
- Precursor cells (aka blast cells) - can only differentiate into one cell type
What are the three different meanings of the term ‘myeloid’
‘Marrow’ e.g. myeloid malignancy
‘Non-lymphoid lineage’ e.g. myeloid lineage
‘Granulocyte’ e.g. myeloid:erythroid ratio
Red vs yellow marrow
Red marrow - haemopoietically active
Yellow marrow - fatty & inactive
Where do HSCs originate from embryonically
The mesoderm
Where is the first site of erythroid activity and how long does this last for?
Yolk sac (stops by week 10)
When does haemopoiesis start in the liver
By week 6
When does haemopoiesis start in the bone marrow
By week 16
Where does haemopoiesis occur in an adult
Bone marrow of axial skeleton, pelvis, & proximal long bones
When does haemopoiesis start in the spleen
By week 10
Where would you take a bone marrow biopsy from in an adult vs child (less than 18 months)
Adult - Posterior superior iliac spine (PSIS)
Child (less than 18 months) - Leg bone e.g. tibia
Describe the structure of a bone marrow venous sinuses & explain its relevance
- fenestrated endothelium &
- discontinuous basement membranes
- allows blood cells to enter the circulation
Describe the structure (4 components) of bone marrow
- Connective tissue
- Vascular elements (periosteal artery network & sinusoids)
- Haemopoietic cells
- Other cells (adipocytes, fibroblasts, osteoblasts/clasts)
Where do blood cells pass through in the bone marrow in order to enter circulation
Fenestrations in endothelial cells of sinusoids
What changes in the sinusoids are associated with RBC release
Sinusoidal dilatation &
Increased blood flow
How are thrombocytes released into sinusoidal blood vessels
Through proplatelets (long branching processes of megakaryocytes that connect to the sinusoids)
What is the myeloid:erythroid ratio
The M:E ratio indicates the relative numbers of myeloid lineage cells (all granulocytic and monocytic cells) to nucleated erythroid precursors in marrow
What are the three main factors that regulate haemopoiesis
Intrinsic properties of cells (e.g stem cells vs progenitor cells vs mature cells)
Signals from immediate surroundings and the periphery (microenvironmental factors)
Specific anatomical area (‘niche’) for optimal developmental signals
What signalling molecule regulates RBC, neutrophil & platelet production
Erythrocytes - erythropoietin
Neutrophils - granulocyte-colony stimulating factor (G-CSF)
Platelets - thrombopoietin
Describe eosinophil, neutrophil, monocyte & lymphocyte morphology
- Eosinophils - tomatoes with sunglasses
- Neutrophil - multi lobed nucleus, granulocytes
- Monocytes - big chunky cell, single lobed, kidney bean nucleus, ‘ground glass’ cytoplasm
- Lymphocyte - large purple nucleus
What investigations are used to assess haemopoiesis of non-lymphoid mature cells
MORPHOLOGY!
- First line - FBC, cell indices & blood film
- Specialist test - bone marrow examination
What investigations are used to assess haemopoiesis of lymphoid mature cells and why is it different from non-lymphoid mature cells
- Immunophenotyping
- Not blood film as the different lymphoid lineages (& HSCs & progenitors & myeloblasts) are all morphologically similar
How does immunophenotyping work
Identify patterns of protein (antigen) expression unique to a cell lineage
Use antibodies (in combination) specific to different antigens
What is the name of the process that produces erythrocytes
Erythropoiesis
What is the name of the process that produces thrombocytes
Thrombopoiesis
What is the name of the process that produces granulocytes
Myelopoiesis OR granulopoiesis
What is the name of the process that produces monocytes
Monocytopoiesis
What is the name of the process that produces lymphocytes
Lymphopoiesis
Haemopoietic stem cells & progenitor cells are based mainly in the bone marrow in adults. Where would you expect a higher proportion of HSCs in blood than normal
Umbilical cord blood
Where in the bone marrow do macrophage develop
Erythroid islands
What happens to the myeloid:erythroid ratio in acute blood loss
Decreases
What happens to the myeloid:erythroid ratio in haemolysis
Decreases
What happens to the myeloid:erythroid ratio in post pneumonic empyema
Increases
What happens to the myeloid:erythroid ratio in post pneumonic empyema
Increase
Why is morphology not useful for identifying haemopoietic progenitors and/or stem cells?
What technique is helpful to assign lineage to cells when morphology is unreliable?
HSCs & progenitors & myeloblasts & lymphocytes have similar morphology
Immunophenotyping is used instead
Other than bone marrow, where are sinusoids found
Liver & spleen
Immunophenotyping vs immunohistochemistry
Why is bone marrow biopsy not indicated in situations where the change in blood count is reactive?
