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Optimal directional volatile transport in retronasal olfaction
- Source :
- Proceedings of the National Academy of Sciences of the United States of America. 112(47)
- Publication Year :
- 2015
-
Abstract
- The ability of humans to distinguish the delicate differences in food flavors depends mostly on retronasal smell, in which food volatiles entrained into the airway at the back of the oral cavity are transported by exhaled air through the nasal cavity to stimulate the olfactory receptor neurons. Little is known whether food volatiles are preferentially carried by retronasal flow toward the nasal cavity rather than by orthonasal flow into the lung. To study the differences between retronasal and orthonasal flow, we obtained computed tomography (CT) images of the orthonasal airway from a healthy human subject, printed an experimental model using a 3D printer, and analyzed the flow field inside the airway. The results show that, during inhalation, the anatomical structure of the oropharynx creates an air curtain outside a virtual cavity connecting the oropharynx and the back of the mouth, which prevents food volatiles from being transported into the main stream toward the lung. In contrast, during exhalation, the flow preferentially sweeps through this virtual cavity and effectively enhances the entrainment of food volatiles into the main retronasal flow. This asymmetrical transport efficiency is also found to have a nonmonotonic Reynolds number dependence: The asymmetry peaks at a range of an intermediate Reynolds number close to 800, because the air curtain effect during inhalation becomes strongest in this range. This study provides the first experimental evidence, to our knowledge, for adaptations of the geometry of the human oropharynx for efficient transport of food volatiles toward the olfactory receptors in the nasal cavity.
- Subjects :
- Nasal cavity
Models, Anatomic
Multidisciplinary
Time Factors
Experimental model
Chemistry
Exhalation
Anatomy
Olfaction
Mechanics
respiratory system
Middle Aged
Nose
Biological Sciences
Oral cavity
Flow field
3d printer
Smell
medicine.anatomical_structure
medicine
Humans
Female
Volatilization
Entrainment (chronobiology)
Subjects
Details
- ISSN :
- 10916490
- Volume :
- 112
- Issue :
- 47
- Database :
- OpenAIRE
- Journal :
- Proceedings of the National Academy of Sciences of the United States of America
- Accession number :
- edsair.doi.dedup.....e726a66fad57470f59b20d262fa93826