Physical and geometric constraints shape the labyrinth-like nasal cavity

Zwicker, David; Ostilla–Mónico, Rodolfo; Lieberman, Daniel E.; Brenner, Michael P.

doi:10.1073/pnas.1714795115

Cited by 23 publications

(23 citation statements)

References 32 publications

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“…In our model, L does not depend on the sniff wave form, and the velocity is proportional to the measured pressure: u|t∼P|t (Zwicker et al, 2018). The pressure changes due to the air flow have two main terms, the first one is due to the viscosity of the air is a narrow tube, i.e., it is a drag term which is proportional to the air velocity.…”

Section: Resultsmentioning

confidence: 99%

“…We propose a very simple FD model for odor propagation in the nose. Although nasal cavities have complex geometries, the airflow within them is predominantly laminar and thus can be approximated using simple models (Zwicker et al, 2018). Obviously, our simple model does not capture all the subtleties of odor propagation, however, it does provide a reasonable explanation for the observed variability in sniff waveforms which contribute to variability in MT cell odor responses.…”

Section: Discussionmentioning

confidence: 99%

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Sniff Invariant Odor Coding

Shusterman

Sirotin

Smear³

et al. 2018

eNeuro

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Sampling regulates stimulus intensity and temporal dynamics at the sense organ. Despite variations in sampling behavior, animals must make veridical perceptual judgments about external stimuli. In olfaction, odor sampling varies with respiration, which influences neural responses at the olfactory periphery. Nevertheless, rats were able to perform fine odor intensity judgments despite variations in sniff kinetics. To identify the features of neural activity supporting stable intensity perception, in awake mice we measured responses of mitral/tufted (MT) cells to different odors and concentrations across a range of sniff frequencies. Amplitude and latency of the MT cells’ responses vary with sniff duration. A fluid dynamics (FD) model based on odor concentration kinetics in the intranasal cavity can account for this variability. Eliminating sniff waveform dependence of MT cell responses using the FD model allows for significantly better decoding of concentration. This suggests potential schemes for sniff waveform invariant odor concentration coding.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Sniff Invariant Odor Coding

Shusterman

Sirotin

Smear³

et al. 2018

eNeuro

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“…Given that there has been considerable discussion and conflicting views regarding the presence of laminar or turbulent flow within the nose with studies involving physical models, mathematical models and numerical methods (29,30,(47)(48)(49)(50) , this study has provided a unique alternative method of analysis. In particular, the estimate of the critical Reynold number can be obtained from rhinomanometric data and therefore has the potential for clinical use where abnormal flow is suspected such as in those cases listed at the beginning of the introduction.…”

Section: Discussionmentioning

confidence: 99%

Modelling nasal airflow coefficients: an insight into the nature of airflow

Neill¹,

Tolley²

2020

Rhin

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Background: There has been considerable discussion and conflicting views regarding the presence of laminar or turbulent flow within the nose. The aim of this study was to investigate how the modelling of variable flow coefficients can assist in the evaluation of the characteristics of flow in the resistive segments of the nose. Methodology: A comparison was made between the flow coefficient for the nasal valve, obtained from a mathematical model, and resistive flow components such as a Venturi meter and orifice tube. Also, a variable loss coefficient was formulated for the whole (unilateral) nose which, by utilising the intersection of the laminar and turbulent asymptotes, provided an estimation for the critical Reynolds number (R crit). Results: The results show that the flow resistance of the nasal valve is considerably greater than that for both a Venturi meter and an orifice tube implying turbulent or turbulent-like flow for much of nasal inspiration. Regarding the loss coefficient for the whole (unilateral) nose, normal respiration flowrates are displaced well away from the laminar asymptote. The critical Reynolds number was estimated to be 450. Conclusions: A novel method of determining the flow characteristics of the nose, particularly the critical Reynolds number, is presented. The analysis indicates a higher degree of turbulence than is assumed from a simple traditional calculation using a hydraulic diameter and flow through straight tubes. There are implications for computational fluid dynamics (CFD) modelling where either the entire nasal airflow is assumed to be laminar or a low turbulence model implemented.

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“…Clearly, the human ability to orient to odors is not as highly developed as that of olfactory specialists, such as the domestic dog. First, the human internal nasal chamber is smaller than expected for a mammal of its body size (Zwicker et al, 2018). Its chamber lacks an olfactory recess, a feature found in the domestic dog that separates the olfactory air stream from the respiratory air stream.…”

Section: Human Olfactory Navigationmentioning

confidence: 98%

“…A new computational study of air flow in the mammalian nasal skeleton called even the assumption of turbulence into question. This model of the role of passage geometry in fluid mechanics concluded that the nasal passage is optimized to produce a laminar, not turbulent, airflow (Zwicker et al, 2018). This does not mean that the human nose does not condition air.…”

Section: Introductionmentioning

confidence: 99%

The navigational nose: a new hypothesis for the function of the human external pyramid

Jacobs

2019

Journal of Experimental Biology

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One of the outstanding questions in evolution is why Homo erectus became the first primate species to evolve the external pyramid, i.e. an external nose. The accepted hypothesis for this trait has been its role in respiration, to warm and humidify air as it is inspired. However, new studies testing the key assumptions of the conditioning hypothesis, such as the importance of turbulence to enhance heat and moisture exchange, have called this hypothesis into question. The human nose has two functions, however, respiration and olfaction. It is thus also possible that the external nose evolved in response to selection for olfaction. The genus Homo had many adaptations for long-distance locomotion, which allowed Homo erectus to greatly expand its species range, from Africa to Asia. Long-distance navigation in birds and other species is often accomplished by orientation to environmental odors. Such olfactory navigation, in turn, is enhanced by stereo olfaction, made possible by the separation of the olfactory sensors. By these principles, the human external nose could have evolved to separate olfactory inputs to enhance stereo olfaction. This could also explain why nose shape later became so variable: as humans became more sedentary in the Neolithic, a decreasing need for long-distance movements could have been replaced by selection for other olfactory functions, such as detecting disease, that would have been critical to survival in newly dense human settlements.

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Physical and geometric constraints shape the labyrinth-like nasal cavity

Cited by 23 publications

References 32 publications

Sniff Invariant Odor Coding

Sniff Invariant Odor Coding

Modelling nasal airflow coefficients: an insight into the nature of airflow

The navigational nose: a new hypothesis for the function of the human external pyramid

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