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PNAS:新型3D模型阐明人类鼻后嗅觉机制

来源:生物谷 2015-11-16 11:55

图片来源:medicalxpress.com

2015年11月16日 讯 /生物谷BIOON/ --薄荷糖的香味可以通过鼻腔仔细品味,这种香味可以进入鼻腔遍布于机体鼻腔中嗅觉感受器所存在的地方,但研究者目前并不清楚具体的分子机理,日前一项刊登在国际著名杂志PNAS上的研究论文中,来自耶鲁大学的科学家们就构建了一种新型3D模型来帮助解析这种现象发生的本质。

研究者Gordon Shepherd教授表示,本文研究证实,人们尤其会适应增强嗅觉的形式,同时也会增强香味在人类饮食中的中枢性角色;本文研究中来自工程学领域和成像技术的专家经过通力合作开发除了这种新型3D模型,工程学领域的科学家进行了相关的流体动力学研究,而成像领域的科学家则对机体的喉咙进行了全方位的扫描。

研究者表示,他们非常惊讶地发现这种动态流体模式,其或可帮助揭示,口腔背面的口咽或可被经过塑造以使得颗粒可以被收集到一个虚拟的腔体中,在虚拟的腔体中这些颗粒或将通过呼气流被有效地吸入,这个过程就被称之为鼻后嗅觉;相比较而言,机体鼻腔吸入过程中流线就可以正确通过腔体,从而尽可能减小颗粒物进入到肺部的可能性,甚至在我们吃东西正常呼吸的情况下在相对较低的流速情况下这种差异仍可发生。

研究者推测,鼻腔的这种机制或可帮助机体通过鼻后嗅觉快速感知气味,同时伴随触摸和品尝来确定是否我们的嘴里可以接受这种物质;此外挥发物通过吸入进入肺中的机会也被降至最低,因为挥发物会为机体提供一种警示告知机体不要接受这种食物。(生物谷Bioon.com)

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Optimal directional volatile transport in retronasal olfaction

Rui Nia,b,1, Mark H. Michalskic, Elliott Brownc, Ngoc Doand, Joseph Zinterd, Nicholas T. Ouellettea,e, and Gordon M. Shepherdf

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.

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