Abstract

Nasal cavity is an anatomical region of the craniofacial skeleton that is the gate of the respiratory system. This cavity shows strong morphological variation, but the link between its shape and its function is not fully understood. Previous studies focusing on environmental factors (e.g. air temperature, humidity, altitude) demonstrated an influence of these factors on nasal morphology. However, it is difficult to disentangle this environmental influence from genetic, physiological and biomechanical forces that also affect craniofacial shape. Furthermore, nasal cavity is covered by a respiratory epithelium, which produces heat and moisture exchange by convection and evaporation, and thus plays a crucial role in respiratory energetics and air conditioning. This epithelium delimits a passage through which the inspired air travels: the nasal airway. To date, the quantification of modern morphological variation of the nasal airway remains scarce, and so does the test of potential mechanistic hypotheses. This study focuses on in vivo tomographic images of 200 adult individuals recruited in France, South Africa, Russia, Cambodia and Chile. We use diffeomorphism, a landmark-free 3D morphometric approach, to quantify and compare the variation of the nasal shape among and between these five populations. Preliminary results obtained on two samples (France and South Africa) show some inter-population morphological differences, localized mainly in the nasal opening, the upper and middle meati, and the choanae. Within the same population, neither the sex nor the age of the individuals seem to affect the morphology of the nasal airway. This study provides insights into nasal morphology and variation in relation with demographic data. Our results also allow us to question the part played by each force at work (genetic, physiological and environmental factors) in this morphological variation.