Haemopoiesis Flashcards
What is haemopoiesis?
The formation of blood cells
What is the process through which platelets are made?
Thrombopoiesis
What is the process through which granulocytes and monocytes are made?
Granulopoiesis or myelopoiesis
What is the process through which lymphocytes are made?
Lymphopoiesis
What is the red cell lifespan?
120 days
What is the neutrophil lifespan?
7-8hrs
What is the platelet lifespan?
7-10 days
What does ‘blast’ mean?
Primitive nucleated precursor
What is a megakaryocyte?
Platelet precursor, polypoid
What is a myelocyte?
Nucleated precursor between neutrophils and blasts
What are all haemopoietic cells derived from?
Haemopoietic stem cells
What are haemopoietic stem cells derived from?
Mesoderm
When are circulating committed progenitors detectable from?
Early as week 5
When does the yolk sac, the first site of erythroid activity, stop producing cells by?
Week 10
When does the liver, spleen and bone marrow begin haemopoiesis?
Week 6,12 (spleen has small contribution in humans) and 16 respectively
What are the compartments of bone marrow?
Cellular- haemopoietic/non-haemopoietic cells
Vascular elements
Connective tissue matrix
What minute projections of bone are found throughout the metaphysis such that many cells in this region are close to the bone surface?
Trabeculae
What is the interface of bone and bone marrow known as?
Endosteum
What are sinusoids?
Specialised venules that form a reticular network of fenestrated (with apertures) vessels
What do arteries feed into bone?
Sinusoids
What can formed blood cells pass through in endothelial cells to enter circulation?
Fenestrations
Where do neutrophils actively migrate towards?
Sinusoid
What long branching processes do megakaryocytes extend into the sinusoidal blood vessels?
Proplatelets
What marrow is haemopoietically active and fatty inactive?
Red and yellow respectively (increased yellow with age)
How is marrow cellularity calculated?
100-age=cellularity (%)
What is the myeloid:erythroid ratio?
Relationship of neutrophils and precursors to proportion of nucleated red cell precursors (ranges from 1.5:1 to 3.3:1)– can change (eg reversal in haemolysis as a compensatory response)
What regulates haemopoiesis?
Complex interplay of ‘random’ intrinsic properties of cells (particularly stem cells) and signals from immediate surroundings and the periphery (microenvironmental factors)
Activation of lineage-specific transcription factors
What is neutrophil maturation regulated by?
Granulocyte colony stimulating factor (G-CSF)
What does thrombopoietin regulate growth and development of?
Megakaryocytes from their precursors
What does erythroid maturation occur around in the form of islands?
Nurse macrophages
What are the clinical implications of the haemopoietic niche for the haemopoietic stem cell (HSC)?
Niche can shift in states of marrow stress
Drug therapy can be used to mobilise HSC from niche for collection and transportation
How do we assess haemopoiesis?
Routine- blood count, cell indices, morphology
Less common- bone marrow examination
What is the study of antigen expression using specific antibodies?
Immunophenotyping
What are specialist tests for haemopoiesis on rare populations of cells/morphologically indistinguishable cells?
Immunophenotyping
Cytochemistry
Clonogenic assays
Animal models
What does immunophenotyping sense on the antibody-antigen complex?
Fluorochrome
