Blaire Van Valkenburgh and Nancy Rawson University of California-Los Angeles and Monell Chemical Senses Center
The snout of a mammal houses a complex skeleton made up of three paper-thin scrolls of bone known as the turbinates. The largest and most intricate are the maxilloturbinates, which play a critical role in conditioning respired air and minimizing water loss. Above and/or behind them lie the ethmoturbinates, which function in the sense of smell. The smallest are the relatively simple nasoturbinates that lie above the maxilloturbinates and are of uncertain function. Collectively, the turbinates and their chambers make up a third to a half of the volume of the head in most mammals, and yet we know very little about their anatomy and how they vary in size and arrangement among species. Given that complex turbinates appear to be present in the earliest known mammals and are associated with two fundamental features of mammals, olfaction and endothermy (warm-bloodedness), it is remarkable that so little is known about them. This is because their hidden, internal location and delicate structure make them difficult to study. However, recent advances in high-resolution CT scanning (HRCT) opened the door to discovery of mammalian turbinate structure. Preliminary studies on dogs and cats show that turbinates can be visualized with HRCT, revealing these structures in their entirety for the first time. The proposed research will expand and improve upon this previous work, including study of a wider array of mammal species, development of sophisticated image analysis software to quantify turbinate structure, and a histological analysis of tissues covering the turbinates that will distinguish olfactory versus respiratory regions. This study brings together anatomists, histologists, and computer scientists to produce the first quantitative overview of the nose that integrates both histological and skeletal data in any group of mammals. It will establish the groundwork for much future research on turbinate function. Undoubtedly, some of the most interesting questions about turbinate function (both olfactory and respiratory) concern aspects of flow through the nose. How is air directed to or away from olfactory areas? Is it possible to direct air to maximize flow during aerobic exercise, or to minimize flow to enhance water and heat conservation? This study will document the basic anatomical framework of mammalian turbinates for the first time, and provide fundamental information necessary for understanding nasal function and disorders involving smell and respiration in mammals, including humans. Graduate and undergraduate students will be trained through this project. The CT scans will be entered into the Digimorph library, and will therefore be accessible to the public and broader scientific community. The PI has plans to develop aspects of this research for use by teachers in disadvantaged L.A. school science curricula.
