Question

Explain the formation and maturation of blood cells from stem cells

Answer 1

• Hematopoiesis is the process of formation of blood cells from pluripotent stem cell.
• Red Blood cells and ~70% white blood cells and platelets are originated from bone marrow.
• Remaining portion of population of white blood cells is formed by lymphoid organs i.e. thymus and spleen.
• Hematopoietic stem cells are present in bone marrow which differentiate to form cells of myeloid lineage( RBC, Platelets, WBC'S) and lymphoid lineage ( B cells and T cells).
• Erythropoiesis : formation of RBC's ( myeloid lineage) from hematopoietic stem cells.
• Myelopoiesis : formation of granulocytes(eosinophils, neutrophils, basophils), megakaryocytes (Platelets) and macrophages from hematopoietic stem cell.
• Lymphoiesis : formation of Natural killer cells(NK cells)T, and B cells(lymphoid lineage) from hematopoietic stem cells.
• As a result of alterations in gene expression, potency of stem cells become restricted, therefore limiting the type of cells which can be formed.
• Cell fate determination of hematopoietic stem cells is given by two theories:
• Determinism theory: according to determinism theory colony stimulating factors and other developmental factors laying the path for development which cell will follow to differentiate into a particular cell type.
• Stochastic theory : according to this theory, cells are randomly differentiated into specific cell types.
• Hematopoiesis occurs in yolk sac during embryo development, but along with developmental process it begins to continue in spleen liver and thymus followed by bone marrow.