Metabolism and the Red Cell

Alterations of iron metabolism are intimately related to diseases of the hematopoietic system. Therefore, it is necessary to review some aspects of hematopoiesis before we discuss iron deficiency in detail. 

The hematopoietic system consists of several organs distributed throughout the body and mainly comprises bone marrow, lymph nodes and lymphoid centers, spleen, and thymus. Its most obvious role is to provide the organism with the cellular constituents of the blood. In comparison with liver parenchymal cells, the life span of the circulating blood cell is relatively short. To maintain the steady state of the blood, hematopoiesis needs to be active even throughout adult life [14, 15]. 

The hepatosplenic period starts 3 months after the beginning of pregnancy and is characterized by an intensive hematopoiesis in spleen, thymus, and liver, leading to the formation of white cells and red cells identical to those found in adult blood. Before this 

Five months after the onset of pregnancy, only the bone marrow retains hematopoietic properties under normal conditions. This stage is called the period of myeloid hematopoiesis. Thus, the bone marrow, which at first provided the cells of the white lineage primarily, soon becomes the main source of all the cellular elements in the blood. However, the lymph nodes and the spleen may reactivate their myelopoietic properties under specific physiological or pathological conditions. 

The hematopoietic organs contain a network of richly interconnected fibers. The chemical nature of the fiber is not established, but the fiber has the staining properties of reticulin. Cells resembling fibroblasts are found along the network, and a great number of different cells are in the meshes of these webs. All these cells are hematopoietic cells at one or another stage of maturation mature cells (lymphocytes, polymor-phonuclears) and transitional forms between the mother and the mature cells. In adult humans, only the bone marrow presents all hematopoietic potentialities. Under normal conditions, the lymph nodes, the spleen, and the thymus are responsible for only lymphopoiesis. 

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