noun, plural: myelocytes
(haematology) A precursor cell during granulopoiesis
In haematology, a myelocyte is one of the precursor cells in the granulocytic line. It is found in the bone marrow and develops into a metamyelocyte. The process of forming new blood cellular elements in vertebrates is called hematopoiesis. The hematopoiesis of granulocytes is called granulopoiesis. In the granulocytic series, the developmental stages are as follows: hemocytoblast → common myeloid progenitor (also called CFU-GEMM) → CFU-GM → CFU-G → myeloblast → promyelocyte → myelocyte → metamyelocyte → band cell → granulocyte. A myelocyte is slightly smaller than a promyelocyte. Its size ranges from 10 to 20 μ. The round to oval nucleus is flattened on one side and eccentrically located inside the cell. When viewed under a light microscope, the myelocyte appears to lack a nucleolus (although electron microscopy reveals smaller nucleoli). The chromatin is coarse. The azurophilic granules are relatively fewer than those in promyelocytes.
There are three types of myelocytes: neutrophilic, basophilic, and eosinophilic. When stained with conventional dyes, the neutrophilic myelocyte would have lilac granules, the eosinophic myelocyte, with orange to red granules, and the basophilic myelocytes, with purplish granules. The eosinophilic myelocytes may have purple granules but the granules have a different structure compared with those of the basophilic myelocytes. Both the neutrophilc and the eosinophilic myelocytes have granules positive for peroxidase.
Word origin: Ancient Greek muelós (“marrow”) + -cyte (“cell”)
- common myeloid progenitor cell (haematology)
- promyelocyte (haematology)
- metamyelocyte (haematology)
- hematopoiesis (haematology)
- myelocytic (adjective)