Haematology - Red Blood Cells

Question 1

Haemopoiesis

Answer 1

Formation and development of RBCs, blood cells of all types originate in bone marrow, from pluripotent haemopoietic stem cells (HSCs) throughout life, HSCs -> lymphoid stem cells and myeloid stem cells -> erythrocytes, granulocytes, monocytes and platelets; regulated by genes, transcription factors, growth factors (erythropoietin) and micro environment

Question 2

Cell/intravascular lifespan/major function

Answer 2

Eythrocyte/120 days/O2 transport, neutrophil/7-10hrs/defence (phagocytosis and killing of microorganisms), monocyte/several days/defence (phagocytosis and killing of microorganisms), eosinophil/little less than neutrophil/defence against parasitic infection, lymphocyte/v variable/humoral and cellular immunity, platelet/10 days/haemostasis

Question 3

Numbers

Answer 3

500 billion/caused; HSCs self-renew (some daughter cells remain as HSCs so pool not depleted) and differentiate to mature progeny -> keep numbers and separate control of production of each blood cell

Question 4

Pathway 1 (common myeloid progenitor)

Answer 4

Multipotential hematopoietic stem cell (hemocytoblast) -> common myeloid progenitor -> megakaryocyte (-> platelets), erythrocyte, mast cell, myeloblast (-> neutrophil + basophil + eosinophil (granulocytes), monocyte (-> macrophage))

Question 5

Pathway 2 (common lymphoid progenitor)

Answer 5

Multipotential hematopoietic stem cell (hemocytoblast) -> common lymphoid progenitor -> small lymphocyte (-> T lymphocyte & B lymphocyte (-> plasma cell)) and natural killer cell (large granular lymphocyte)

Question 6

HSCs - Embryo

Answer 6

From mesoderm in yolk sac (primitive RBCs, platelet precursors, macrophages), liver takes over at 6-8 weeks of gestation until shortly before birth, bone marrow hemapoietic activity at 10 weeks, in adults -> bone marrow (esp. pelvis, femur and sternum, also vertebrae and proximal ends of long bones of thigh and arm, femur and humerus, in children all bones)

Question 7

Myeloproliferative disorder (polycythemia)

Answer 7

Increased hemopoietic drive = hemopoietic foci in adult liver and spleen (extramedullar hemopoiesis), expanded hemopoietic tissue (other marrow cavities)

Question 8

Hemopoietic progenitor cells

Answer 8

Alongside HSCs, distributed within bone marrow among mesenchymal cells (multi potent stem cells for making and repairing skeletal tissue), endothelial cells and vasculature with which HSCs interact, disruption of regulation can disturb balance between proliferation and differentiation, may lead to leukaemia/bone marrow failure

Question 9

Hemapoietic growth factors

Answer 9

Except EPO, all in bone marrow, bind to cell surface receptors, glycoprotein hormones, regulate proliferation and differentiation of HSCs, regulate mature blood cells; erythropoietin -> synthesized in kidney, regulates erythropoiesis, stimulated by reduced O2 supply to kidney; granulocyte and monocyte production (neutrophils, eosinophils, basophils) -> cytokines (ie interleukins), G-CSF (granulocyte colony stimulating factor) and G-MCSF (granulocyte macrophage colony stimulating factor); megakaryocytopoiesis and platelet production -> thrombopoietin