ROWE, T. B.; MACRINI, T. E. ; EITING, T. P.; KETCHAM, R. A.; Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78712: The Olfactory and Respiratory Skeleton in the Nose of the Opossum Monodelphis domestica

The internal nasal skeleton in Monodelphis (www.DigiMorph.org) supports olfactory and respiratory epithelia, the vomeronasal organ, and the nasal gland. It is built by the median mesethmoid, which forms the osseous nasal septum, and the paired vomer and ethmoid bones. The ethmoid segregates respiratory and olfactory regions. Its geometry offers insight into the functional, developmental, and genomic organization of the nose. It forms through coalescence of separate turbinals, which in Monodelphis comprise the maxilloturbinal, nasoturbinal, five endoturbinals, and two ectoturbinals. Ethmoidal growth into the lumen of the nasal cavity increases respiratory surface area by a factor of six and olfactory surface by nearly an order of magnitude. Respiratory epithelium warms and humidifies inspired air, recovers exhaled moisture, and mediates brain temperature. The ethmoid olfactory skeleton forms a series of funnels that support growth of new olfactory neurons throughout life. Olfactory mucosa lines the mouth of each funnel, forming blind olfactory recesses known as the ethmoid cells, and neuronal axons are funneled from the epithelium through olfactory foramina in the cribriform plate, into proximity with target glomeruli in the olfactory bulb, where each axon makes its first synapse. The skeleton thus mediates topological correspondence between odorant receptor areas in the nose with particular glomeruli in the olfactory bulb, enabling growth throughout life of new olfactory neurons and proper targeting by their axons. The geometry of odorant receptors suggests that volatility may be a component in the peripheral olfactory code, and that corresponding glomeruli may function in temporal signal processing.