Bone marrow is a major site of lymphocyte formation. It is also the production site for blood platelets.

The purpose of these black and white drawings is to present the main criteria used to identify the steps in the formation of erythrocytes and leukocytes in bone marrow and to present the terminology used in this chapter.

(A similar image is shown in colour in Figure 7.12 to help identify hemopoietic cells in bone marrow smears, as illustrated in figures 7.13 to 7.21.)

(Top left) The first is labelled a stem cell (hemocytoblast). Although it is generally accepted that all blood cells originate from stem cells, the morphological characteristics of these cells are still undetermined and the present drawing is hypothetical.