During maturation, blood cells become smaller, nucleocytoplasmic proportion decreases, the chromatin is condensed and the staining intensifies. The nucleolus disappears, the cytoplasm loses basophilic features, and the cell, by its appearance and content, gets the characteristics of a mature cell. The maturation of the nucleus and cytoplasm in normal blood cells occurs synchronously. Asynchronism in the maturation of the nucleus and cytoplasm is a sign of abnormality. In peripheral blood of healthy people only mature cells of some bloodlines can be found:
- The erythrocytic lineage: erythrocytes and rare reticulocytes;
- The leukocytic lineage: mature granulocytes (segmented granulocytes and few non-segmented neutrophilic granulocytes), mature lymphocytes and monocytes; and
- The thrombocytic lineage: blood platelets - thrombocytes.
All these mature cells have a characteristic appearance. They are unlike each other and can easily be recognized.
In various diseases, cells of an earlier stage can appear in the peripheral blood, as well as the earliest precursors of some lines. On the other hand, mature cells of some lines have a changeable appearance in various diseases Therefore, it is necessary to recognize the cells of the same blood line, differentiate less mature from the immature cells of same blood lines in order to establish the cause of the disease and check the treatment success. All blood cells, from the stem cells to mature cells, pass through different stages of development. During this process, they change in sizes and form of the cell and in traits of the nucleus and cytoplasm. This provides the basis for the differentiation of both the cells of the same bloodline and cells from different cell lines. The cells of the erythrocytic line are the best example for this.
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