ABSTRACT
This chapter reviews the development of the hematopoietic system, hematopoietic processes, structure, function, gross and microscopic appearance of the hematopoietic system and alterations in hematopoiesis as an understanding of these areas is essential in the evaluation of hematotoxicity. While granulocyte progenitors appear in the yolk sac in the mouse, there is little known regarding the ontogeny or embryonic function of the neutrophil lineage derived from yolk sac hematopoiesis. Hematopoietic stem cells' arise at intraembryonic sites during the third wave of prenatal hematopoiesis, and ultimately home to the bone marrow to initiate adult hematopoiesis. Flow cytometric analysis of bone marrow may be used to provide cellular differentials in place of bone marrow smear examination and has the advantage of evaluating many more cells. Hematopoietic cells also appear in the major umbilical and vitelline vessels and placenta. Hematopoiesis is the process by which the cellular components of blood are produced.
