Haemopoiesis Flashcards
What is haemopoiesis?
Formation of blood cells
What is erythropoiesis?
Formation of red blood cells
What is thrombopoiesis?
Formation of platelets
What is myelopoiesis/granulopoiesis?
Formation of granulocytes
What is lymphopoiesis?
Formation of lymphocytes
What is cell production like in the steady state?
Cell loss is balanced by cell production
What cell type would decrease first if haemopoiesis is switched off rapidly?
Neutrophils
What are the steps in red cell production?
Pronormoblast - early normoblast - intermediate normoblast - late normoblast - reticulocyte - erythrocyte
What is the ancestry of neutrophils?
Myeloblast - promyelocyte - myelocyte - metamyelocyte - band neutrophil - neutrophil
What is the progenitor cell of platelets?
Megakaryocytes
What do precursor cells develop from?
Mononuclear haemopoietic progenitor cells produced by haemopoietic stem cells
What can mutlipotent progenitors give rise to?
Both myeloid (non-lymphoid) and lymphoid progeny
What ability to stem cells have that is unique to them?
Ability to self-renew = this ability is lost as they differentiate and mature
What state are most primitive progenitors (e.g stem cells) in during steady state haemopoiesis?
They are dormant
Where do stem cells originate from embryologically?
The mesoderm
How early in development are circulating committed progenitors detectable?
As early as week 5
Where is the first site of erythroid activity during development?
The yolk sac = stops by week 10
Liver starts by week 6 and bone marrow by week 10
Where is haemopoiesis restricted to in adults?
The bone marrow of axial skeleton, pelvis and proximal long bones
Where can bone marrow biopsies be taken from?
Iliac crest in adults
Lower leg can be used in younger children
What does the cellular compartment of the bone marrow contain?
Haemopoietic cells and non-haemopoietic cells (e.g adipocytes)
What are the microscopic features of the bone marrow?
Cellular compartment, connective tissue matrix and vascular elements
What vessels supply blood to the bone marrow?
The nutrient artery and periosteal network = bone marrow consumes 10-15% of cardiac output
Where do arterioles of the bone marrow drain?
Into sinuses which further open into larger central sinuses
How are sinusoids different from capillaries?
They are larger and have a discontinuous basement membrane
How are sinusoids distributed in the bone marrow?
Radially around the central vein
How are mature red cells released from the bone marrow into circulation?
They pass through fenestrations in endothelial cells
What is release of mature red cells associated with?
Sinusoidal dilation and increased blood flow
How do neutrophils enter the circulation form the bone marrow?
Actively migrate towards sinusoids down a chemokine gradient
How do platelets enter the circulation from the bone marrow?
Megakaryocytes extend long branching processes called proplatelets into the sinusoidal blood vessels
What are the different types of bone marrow?
Red marrow = haemopoietically active
Yellow marrow = fatty and inactive
How does the type of bone marrow present change over time?
Increase in yellow marrow with age = older patients have reduced marrow cellularity
What is the myeloid:erythroid ratio?
Relationship of neutrophils and precursors to proportion of nucleated red cell precursors
What happens to the myeloid:erythroid ratio in haemolysis?
Reverses as there is an increase in erythroid production
What are some regulators of haemopoiesis?
Intrinsic properties of cells
Signals form immediate surroundings and periphery
Haemopoietic niche
What is the haemopoietic niche?
Specific anatomical area for optimal developmental signals
What is the regulator of neutrophil precursor maturation?
G-CSF
What regulates the growth and development of megakaryocytes from their precursors?
Thrombopoietin
What are some investigations for haemopoiesis?
Routine = blood count, cell indices, morphology
Less common = bone marrow examination
What are the investigations for mature non-lymphoid cells?
Blood count and morphology often enough
Cytochemistry rarely used
How are mature lymphoid cells investigated?
Immunophenotyping = often require expression of antigens indicating lineage or stage of development
What are the investigations for immature cells?
Immunophenotyping, clonogenic assays, animal models
What is the purpose of immunophenotyping?
Identifies patterns of antigen expression unique to a cell lineage = use antibodies specific to different antigens
How is immunophenotyping carried out?
Label cells with fluorochrome = emits certain colour of light when hit with a laser beam
