Neutrophilic metamyelocyte

Scheme electron microscopy. From CFU-S (colony forming units-spleen) stem cells arise CFU-GM (colony forming unit-granulocyte/monocyte) stem cells. The latter divide by mitoses and differentiate via promyeloblasts and myeloblasts into neutrophilic myelocytes (the last proliferative stage). The next stages are postmitotic cells, termed neutrophilic metamyelocytes and subsequently the young and mature forms of neutrophilic granulocytes. Soon nuclear indentations in neutrophilic myelocytes appear and they become more distinct in later stages (metamyelocytes). Metamyelocytes (12-15 μm) show a kidney-shaped nucleus with a scanty cytoplasm but granules of varying sizes and densities are distinct present. The primary ('non-specific' or azurophilic) granules are electron-grey (2) and contain among others acid phosphatase and arylsulfatase. The secondary (specific) electron-dense granules (1) contain lysozyme and phagocytin