Paranasal sinus drainage is mediated by mucociliary transport and gravity.However, human orthograde posture, along with the superior positioning of the maxillary sinus (MS) ostium, increases reliance on the mucociliary system.Previous research has thus suggested that differences in MS size and shape may impede mucociliary clearance, potentially contributing to disparities in sinusitis susceptibility. To further investigate this hypothesis, this study collected 29 three-dimensional (3D) coordinate landmarks and seven linear measurements of MS morphology from 167 computed tomography (CT) scans of crania of European, East Asian, or Equatorial African ancestry. MANOVA results reveal the Asian-derived individuals are characterized by both a significantly taller MS (F = 14.15, p < 0.0001) and a significantly greater distance from the MS floor to the ostium (F = 17.22, p < 0.0001) compared to those of European and African ancestry. A canonical variate (CV) analysis conducted on 3D landmark data provides corroborative results, distinguishing Asianderived individuals predominantly on the basis of a relatively lower MS floor.As a greater distance between the MS floor and ostium may impede mucociliary clearance, our results suggest MS anatomy may be a more prominent factor in chronic sinusitis among individuals of Asian ancestry compared to those of European and African ancestries. This provides tentative evidence of an anatomical etiology for chronic sinusitis even in the absence of anatomical variants/abnormalities (e.g., nasal polyps, concha bullosa, Haller's cells, and Agger nasi cells). Further research into the relationship between MS anatomy and sinusitis, in addition to socioeconomic inequalities of healthcare, is warranted to continue evaluating possible contributions to health disparities.

Objectives: Although research into human maxillary sinus (MS) morphology has overwhelmingly focused on sinus volume, other aspects of morphology (e.g., overall shape, mucosal surface area) factor prominently in hypotheses regarding MS form and function. Here, we investigate MS volume in conjunction with measures of MS shape and surface area in a large, diverse sample of modern humans. We test whether variation in MS volume is associated with predictable changes in MS shape (i.e., allometry) and investigate the influence of MS size-shape scaling on mucosal surface area dynamics.Materials and Methods: Measures of MS volume and surface area were obtained from computed tomographic (CT) scans of 162 modern human crania from three ancestral backgrounds-Equatorial Africa, Europe, and East Asia. 3D coordinate landmarks and linear measurements were also collected. Multivariate analyses were employed to test for associations between MS volume and other morphological variables.Results: Significant associations between MS volume and 3D shape were identified both across and within the subsamples. Variation in MS volume was found to predominantly relate to differences in MS height and width dimensions relative to MS length. This pattern of allometric scaling was found to differentially influence total mucosal surface area and the SAV ratio. Conclusion:This study suggests that variation in MS volume is disproportionately mediated by MS width and height dimensions. This finding has implications for hypotheses which structurally link MS morphology to craniofacial ontogeny and those which suggest that MS morphology may perform adaptive physiological functions.

Anthropologists have long posited that geographic‐mediated associations between human nasal morphology and climate evince climatic adaptation. These arguments overwhelmingly focus on the prominent role of the nose in respiratory air‐conditioning, as intranasal heat and moisture exchange in different climates is governed anatomically via the amount of nasal mucosa surface area relative to the volume of air passing through each nasal passage. Yet, the inability to quantitatively account for the nasal cycle (a physiological process in which the left and right nasal passages reciprocally alternate in their mucosal congestion levels) has limited investigation into the adaptive influence of nasal soft‐tissues. Accordingly, the goals of this study were to 1) develop protocols for accurately modeling the three‐dimensional (3D) anatomy of nasal airways with in silico controlled variation in mucosal congestion, and 2) test the hypothesis that mucosal surface area‐to‐volume ratios (SA/V) remain constant throughout the nasal cycle. A computed tomography (CT) scan of one male human head was selected for use in the development of protocols for controlling congestion levels via digital expansion/contraction of the nasal mucosa in Amira‐Avizo. These protocols were then used to generate a fully decongested (left/right = 0/0%) nasal airway model for use as an anatomical baseline comparator. Models were then generated for two different phases of the nasal cycle: asymmetrical (left/right = 90/10%) and mid‐cycle (left/right = 50/50%). Nasal passage surface areas and volumes were collected for each model to permit comparisons of SA/V ratios across different mucosal congestion levels. Following theoretical expectations, the decongested model exhibited a substantially lower SA/V (0.57) than the mid‐cycle (0.72) and asymmetrical (0.74) models. Unilateral analyses also met anatomical expectations, with the highly congested left nasal passage of the asymmetrical model demonstrating a higher SA/V (1.06) compared to the same left passage in the mid‐cycle (0.84) and decongested (0.60) models. Cumulatively, these results suggest that the developed 3D digital methods permit reliable in silico modeling of nasal soft‐tissues, allowing future studies to control for mucosal congestion while investigating the role of nasal morphology on respiratory airflow (using computational fluid dynamics analysis, etc.). Moreover, the similar overall SA/V ratios of the two nasal cycle models appear consistent with the hypothesis that, despite morphological asymmetry, the nose’s overall SA/V and air‐conditioning capacity likely remains relatively stable throughout the nasal cycle. Thus, our study suggests that, rather than morphological variability within the nasal cycle, it is the distinction between the semi‐congested nasal cycle versus complete mucosal decongestion (as seen during strenuous exercise) that may confound functional interpretations of ecogeographic variation in nasal morphology. Consequently, further research is needed to determine how these disti...