U01.10.004 Hematopoiesis

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Learning Objective

Describe the hierarchy of hematopoietic stem cells, the differentiation pathways into myeloid and lymphoid lineages, and the major cell types produced in blood and bone marrow.

Stem Cells

  • Multipotent hematopoietic stem cell → gives rise to:
    • Myeloid stem cell
    • Lymphoid stem cell

Myeloid Lineage (Bone Marrow / Blood)

Progenitor Intermediate / Precursor Mature Cell Notes
Myeloid stem cell Erythroblast → Reticulocyte → Erythrocyte RBC Oxygen transport
Myeloid stem cell Megakaryoblast → Megakaryocyte → Platelets Platelets Hemostasis
Myeloid stem cell Myeloblast → Band cell → Granulocytes Neutrophil, Basophil, Eosinophil Innate immunity
Myeloid stem cell Monoblast → Monocyte → Macrophage Macrophage Phagocytosis, antigen presentation

Lymphoid Lineage (Bone Marrow / Thymus / Blood)

Progenitor Precursor Mature Cell Notes
Lymphoid stem cell Lymphoblast B cell → Plasma cell Antibody production
Lymphoid stem cell Lymphoblast T cell → T-helper / T-cytotoxic cell Cell-mediated immunity
Lymphoid stem cell Lymphoblast NK cell Innate cytotoxicity

Key Points

  • Erythropoiesis → RBC formation; reticulocyte is the immediate precursor.
  • Thrombopoiesis → Platelets from megakaryocytes.
  • Granulocytopoiesis → Neutrophils, eosinophils, basophils.
  • Monocytopoiesis → Monocytes → tissue macrophages.
  • Lymphopoiesis → B cells, T cells, NK cells; T cells mature in the thymus.

Activity

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