n. the process of red blood cell (*erythrocyte) production, which normally occurs in the blood-forming tissue of the *bone marrow. The ultimate precursor of the red cell is the *haemopoietic stem cell, but the earliest precursor that can be identified microscopically is the *proerythroblast. This divides and passes through a series of stages of maturation termed respectively early, intermediate, and late *normoblasts, the latter finally losing its nucleus to become a mature red cell. See also haemopoiesis.
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 (*erythrocytes). 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.... erythroblast
(red blood cell) n. a *blood cell containing the red pigment *haemoglobin, the principal function of which is the transport of oxygen. A mature erythrocyte has no nucleus and its shape is that of a biconcave disc, approximately 7 ?m in diameter. There are normally about 5 ×1012 erythrocytes per litre of blood. See also erythropoiesis.... erythrocyte
(haematopoiesis) n. the process of production of blood cells and platelets which continues throughout life, replacing aged cells (which are removed from the circulation). In healthy adults, haemopoiesis is confined to the *bone marrow, but in embryonic life and in early infancy, as well as in certain diseases, it may occur in other sites (extramedullary haemopoiesis). See also erythropoiesis; leucopoiesis; thrombopoiesis. —haemopoietic adj.... haemopoiesis
n. a nucleated cell that forms part of the series giving rise to the red blood cells and is normally found in the blood-forming tissue of the bone marrow. Normoblasts pass through three stages of maturation: early (or basophilic), intermediate (or polychromatic), and late (or orthochromatic) forms. See also erythroblast; erythropoiesis.... normoblast
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