- Originally, a term denoting all forms of human red blood cells containing a nucleus, both pathologic ( i.e., megaloblastic) and normal ( e.g., normoblastic). The pathologic or megaloblastic series is observed in pernicious anemia in relapse. The term megaloblast is also used to indicate the first generation of cells in the red blood cell series that can be distinguished from precursor endothelial cells; hence with this usage, megaloblast denotes both a normal and an abnormal cell. In the erythrobastic series of maturation four stages of development can be recognized: 1) proerythroblast, 2) basophilic e., 3) polychromatic e., and 4) orthochromatic e.. In the megaloblastic series of maturation, stages similar to those found in the normoblastic series are seen: 1) promegaloblast, 2) basophilic megaloblast, 3) polychromatic megaloblast, and 4) orthochromatic megaloblast. In the normal series of maturation, after loss of the nucleus, young erythrocytes are called reticulocytes; these cells may be recognized with supravital stains such as brilliant cresyl blue; ultimately the reticulocytes become erythrocytes, or mature red blood cells. SYN: erythrocytoblast. [erythro- + G. blastos, germ]
* * *eryth·ro·blast i-'rith-rə-.blast n a polychromatic nucleated cell of red marrow that synthesizes hemoglobin and that is an intermediate in the initial stage of red blood cell formation broadly a cell ancestral to red blood cells compare NORMOBLASTeryth·ro·blas·tic -.rith-rə-'blas-tik adj
* * *n.any of a series of nucleated cells (see normoblast, proerythroblast) that pass through a succession of stages of maturation to form red blood cells (erythrocyte). Erythroblasts are normally present in the blood-forming tissue of the bone marrow, but they may appear in the circulation in a variety of diseases, (see erythroblastosis). See also erythropoiesis.
* * *eryth·ro·blast (ə-rithґro-blast) [erythro- + -blast] a term originally used to indicate any type of nucleated erythrocyte, but now usually limited to one of the nucleated precursors of an erythrocyte, i.e. one of the developmental stages in the erythrocytic series (q.v.), in contrast to a megaloblast. In this usage, it is called also normoblast. erythroblastic adj
Medical dictionary. 2011.