Main events of erythropoiesis
During the formation of erythrocytes, the stem cells called proerythroblasts decrease considerably in size, the chromatin of the nuclei becomes increasingly dense, dark and granular. The cytoplasm stains in blue due to the large amount of RNA present in it. This cell is called basophilic erythroblast.
As these cells continue their differentiation, they begin to synthesise hemoglobin. The cytoplasm begins to stain with a mixture of basophilic and acidophilic dyes due to the coexistence of RNA and hemoglobin – this cell is the .polychromatophilic erythroblast.
With the gradual loss of cytoplasmic RNA, the cells take on the color of a red blood cell – this is the orthochromatic erythroblast.
Nas últimas etapas deste processo o núcleo é expulso da célula originando um eritrócito ou hemácia.
As these cells differentiate, they begin the synthesis of hemoglobin. Because of this, the cytoplasm begins to stain with a mixture of basophilic and acidophilic dyes due to the coexistence of RNA and hemoglobin – this cell is the polychromatophilic erythroblast
In the final stages of this process, the nucleus is expelled from the cell, giving rise to an erythrocyte or red blood cell.
Main events of granulocytopoiesis
The granulocytic lineage stem cells are large and have a voluminous nucleus of loose and delicate chromatin. Its cytoplasm stains in blue but less so than the cytoplasm of the proerythroblast. This cell is called a myeloblast.
During the following stages of differentiation, the cells decreasess in size, the chromatin of the nucleus gradually becomes denser, more stained, and there is a progressive accumulation of specific granules, characteristic of each adult granulocyte lineage.
Myeloblasts give rise to promyelocytes, different for each sublineage: neutrophilic, eosinophilic, and basophilic promyelocyte.
In the next stage, the myelocytes exhibit a notch in the nuclei, that is, an indentation.
In the next stage, the metamyelocyte stage, the cells are considerably smaller, approximately the size of a red blood cell or a neutrophil. Their nucleus is elongated like a sausage, in the shape of a letter U or C, sometimes slightly twisted.
A few cells of the next stage are already found in small quantities in the circulating blood: cells with a rod-shaped nucleus called band cells. Neutrophil band cells exist in a small percentage in normal blood, which is not the case with eosinophil and basophil band cells.
The last stage is the one that corresponds to the mature cells normally found in the circulating blood: segmented neutrophil, segmented eosinophil, and segmented basophil.