Applied Research Laboratory, The Pennsylvania State University, University Park, PA 16802, USA.
J R Soc Interface. 2010 Jun 6;7(47):933-43. doi: 10.1098/rsif.2009.0490. Epub 2009 Dec 9.
The canine nasal cavity contains hundreds of millions of sensory neurons, located in the olfactory epithelium that lines convoluted nasal turbinates recessed in the rear of the nose. Traditional explanations for canine olfactory acuity, which include large sensory organ size and receptor gene repertoire, overlook the fluid dynamics of odorant transport during sniffing. But odorant transport to the sensory part of the nose is the first critical step in olfaction. Here we report new experimental data on canine sniffing and demonstrate allometric scaling of sniff frequency, inspiratory airflow rate and tidal volume with body mass. Next, a computational fluid dynamics simulation of airflow in an anatomically accurate three-dimensional model of the canine nasal cavity, reconstructed from high-resolution magnetic resonance imaging scans, reveals that, during sniffing, spatially separate odour samples are acquired by each nostril that may be used for bilateral stimulus intensity comparison and odour source localization. Inside the nose, the computation shows that a unique nasal airflow pattern develops during sniffing, which is optimized for odorant transport to the olfactory part of the nose. These results contrast sharply with nasal airflow in the human. We propose that mammalian olfactory function and acuity may largely depend on odorant transport by nasal airflow patterns resulting from either the presence of a highly developed olfactory recess (in macrosmats such as the canine) or the lack of one (in microsmats including humans).
犬类鼻腔内有数亿个感觉神经元，位于鼻腔卷曲鼻甲的嗅上皮中，这些鼻甲位于鼻子后部的凹陷处。传统上对犬类嗅觉敏锐度的解释包括感觉器官的大小和受体基因库大，但忽略了嗅探过程中气味传输的流体动力学。但是，气味向鼻子的感觉部分的传输是嗅觉的第一个关键步骤。在这里，我们报告了犬类嗅探的新实验数据，并证明了嗅探频率、吸气气流率和潮气量与体重的比例关系。接下来，我们对犬类鼻腔的一个解剖学上精确的三维模型进行了计算流体动力学模拟，该模型是根据高分辨率磁共振成像扫描重建的，结果表明，在嗅探过程中，每个鼻孔都可以采集到空间上分离的气味样本，这些样本可用于双侧刺激强度比较和气味源定位。在鼻子内部，计算结果表明，嗅探时会出现一种独特的鼻腔气流模式，这种模式优化了气味向鼻子的嗅觉部分的传输。这些结果与人类的鼻腔气流形成鲜明对比。我们提出，哺乳动物的嗅觉功能和敏锐度可能在很大程度上取决于由鼻腔气流模式引起的气味传输，而鼻腔气流模式是由高度发达的嗅觉隐窝（如犬类中的嗅隐窝）或缺乏嗅隐窝（包括人类在内的微嗅体）所导致的。
