Haemopoiesis Flashcards
What is haemopoiesis?
Production of blood cells
Where does the fetus get blood cells from?
Liver and spleen in vascular sinuses, bone marrow
Where does a child get blood cells from?
Bone marrow (progressive loss from limb bones)
Where does an adult get blood cells from?
Bone marrow (mainly in the axial skeleton - vertebrae, ribs, skull, sternum, pelvis)
Name the different types of stem cells.
Totipotent stem cells
Pluripotent stem cells
Adult stem cells
Committed stem cells
Describe totipotent stem cells.
Embryonic development, can form any tissue
Describe pluripotent stem cells.
Increasing specialization to produce a limited range of cell types (e.g. cannot form placenta cells)
Define adult stem cells and where they are found.
Progenitor cells (e.g. haemopoietic progenitor/stem cell). Present in marrow, low numbers in blood. May be able to enter other tissues and participate in healing.
What are committed stem cells?
Myeloid, lymphoid cell lineages
What are the stages of erythroblast formation?
Proliferation
Iron uptake
Hb production
Removal of mitochondria, ER, ribosomes, golgi and loss of nucleus.
Name the regulators of haemopoiesis.
Cytokine/growth factors (induce growth and differentiation of stem cells into mature cells)
Marrow stromal cells (cell surface signals)
Describe how haemopoiesis is an integrated process.
Results in the renewal of pluripotent stem cells. Differentiation of some pluripotent stem cells into specific cell lineages - irreversible. Feedback signals (cytokines/growth factors) from peripheral tissues provide important regulatory control
What provides regulatory control for the integrated process of haemopoiesis?
Cytokines and growth factors from peripheral tissues
What regulatory signals act on stromal cells?
IL-1
TNF
What regulatory signals act on pluripotent stem cells?
Stem cell factor (SCF)
Flt ligand
What regulatory signals act on multipotential progenitor cells?
IL-3, GM-CSF, G-CSF, IL-6, TPO
What regulatory signals act on committed progenitor cells?
G-CSF, M-CSF, IL-5, Erythropoietin, thrombopoietin
Name the committed cells involved in erythropoiesis - the order of formation of an erythrocyte.
Proerythroblast (1-2 days)
Basophilic erythroblast (1-2 days)
Polychromatic erythroblast (3-4 days) - buds off nucleus to become…
Reticulocyte (3-4 days)
Marrow stages 8-9 days
Reticulocyte then buds off into blood to become an erythrocyte.
What is the difference between erythroblast and erythrocyte?
Erythroblast = has nucleus Erythrocyte = nucleus has been discarded
Define viscosity
Cells suspended in plasma
Describe the flow characteristics in microvasculature.
Axial streaming of red cells
Platelet rich plasma zone at periphery
