| Περίληψη: | Hemopoiesis is a complex process which ensures the normal production of blood cells in roder to compensate for those lost during their function. Hemopoiesis is regulated through a large array of molecules which are secreted by the cellular microenvironment, other specific cells and, in some instances, by the hemopoietic cells. It is through these mechanisms that hemopoiesis may meet increased demands. At the end of fetal life the principal site of hemopoiesis is the bone marrow; the other sites are fading. Hemopoiesis starts from a small number of primitive cells, which lie in the marrow but cannot be recognized; these “stem”cells have the capacity to multiply and, at the same time, to secure their own reproduction. In a second phase, stem cells are committed for differentiation towards one of the main hematogical series (red cells, myeloid-monocytoid, megakaryocytic and lymphoid). Subsequently, the committed precursor cells (which can be identified morphologically) continue their proliferation and differentiate to the respective mature blood cells, which leave the marrow and enter in the circulation in order to carry out their multiple functions.
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