Granulopoiesis

This composite image shows the different stages of granulopoiesis for a neutrophil. Granulopoiesis begins when the myeloblast differentiates into a neutrophilic promyelocyte that is irreversibly committed to the neutrophilic cell line. Promyelocyte are large cells with purple-staining nonspecific azurophilic granules. Promyelocytes develop into myelocytes that are characterized by the presence of smaller specific or secondary granules. During this stage the number of specific granules per cell increases and the number of azurophilic granules per cell decreases, resulting in a loss of cytoplasmic basophilia. Granule production ceases at the end of the myelocyte stage and the remaining stages are characterized primarily by a reduction in cell size and a change in nuclear shape. When the nucleus becomes flattened and the chromatin further condensed, the cell is called a metamyelocyte. When the nucleus becomes horseshoe-shaped, it is called a band cell. The cell is considered a mature neutrophil when the nucleus becomes segmented into lobes.