Structure of Masera's Septal Olfactory Organ in Cat (Felis silvestris f. catus) - Light Microscopy in Selected Stages of Ontogeny

The septal organ /SO/ (Masera's organ /MO/) is a chemoreceptor presently considered one of three types of olfactory organs (along with the principal olfactory region and vomeronasal organ). Notwithstanding the septal organ having been first described by Rodolfo Masera in 1943, little is known of the properties of sensory neurons or of its functional significance in chemoreception. Until now the septal organ has been described only in laboratory rodents and some marsupials. This work refers to its existence in the domestic cat (Felis silvestris f. catus). The septal organ can be identified at the end of embryonic period - 27 or 28 days of ontogenesis in cats (the 6th developmental stage of Štěrba) - coincident with formation of the principal olfactory region in nasal cavity. At 45 days of ontogenesis (the 9th developmental stage of Štěrba), this septal olfactory organ is of circular or oval shape, 120 μm in diameter, in ventral part of septum nasi, lying caudally to the opening of ductus incisivus. The structure of the epithelium of septal olfactory organ is clearly distinct from the respiratory epithelium of the nasal cavity. It varies in thickness, cellular composition, as well as free surface appearance, and even lack the typical structure of sensory epithelium, in this developmental period. Nerve bundles and glandular acini are lacking in the lamina propria mucosae of the septal organ and in the adjacent tissues. Glands appear as the single non-luminized cords of epithelia extending from the surface. The adjacent respiratory epithelium contains numerous goblet cells