 Axonal growth is guided by the glial composition and cytoarchitecture of the olfactory bulb in addition to the presence of olfactory ensheathing cells (OECs).It is postulated that OECs originate in the olfactory placode, suggesting a different developmental origin than other similar nervous system microglia.Another interesting concept is that OECs are found in both the peripheral and central nervous system portions of the primary olfactory system, that is, the olfactory epithelium and bulb.