A computer-generated graphic shows how far back one nasal cavity can go. Scientists say the cavity has a complex shape that affects how we detect scents.
英國倫敦的帝國學(xué)院科學(xué)家丹尼斯·多爾利和羅伯特·施羅特爾最近在“英國生物技術(shù)生物科學(xué)研究協(xié)會”的刊物《使命》上發(fā)表文章披露,，在鼻子里面的小小的鼻腔里,，被吸入的空氣的流動并不平靜和簡單，而是會形成渦流,，而且流動狀況非常復(fù)雜,。
研究小組首先根據(jù)對一系列受試者的鼻子的CT掃描結(jié)果，用透明的物質(zhì)制作了比例放大一倍的鼻子模型,，這個模型準(zhǔn)確地模擬了人的鼻腔結(jié)構(gòu),。然后他們讓水流過該鼻子模型，并用數(shù)碼相機對流動狀況進行拍攝,。為了便于觀察,，他們還在水中加入微細的塑料顆粒,，便于拍攝。由于空氣在鼻腔中的流動速度很慢,，從流體力學(xué)觀點上看,，用水代替空氣是可以的。
通過調(diào)節(jié)水進入鼻腔模型的狀況,，科學(xué)家可以模擬從平靜呼吸到打噴嚏等所有的呼吸情況,，都發(fā)現(xiàn)水流在前進的同時還“打旋”，形成渦流,。多爾利指出,，鼻腔通道沒有筆直的，它們的曲線也不是流線型的,，這樣就使氣流非常復(fù)雜,。他說，“大家都以為,，空氣繞飛機機翼的流動很復(fù)雜,，其實，這一運動比空氣在鼻腔中的流動還容易被人理解,，而且即使在心臟中血液的流動,，也比鼻腔中空氣的流動來得簡單。”
科學(xué)家認為,，正是因為鼻腔具有復(fù)雜的結(jié)構(gòu),，才使空氣在鼻腔中的流動如此復(fù)雜，從而使那些吸進鼻腔的能引起嗅覺器官反應(yīng)的物質(zhì),，最佳地分配到所有嗅覺細胞上,，保證嗅覺的靈敏。人感冒后會引起鼻黏膜腫大,，這個時候嗅覺就不靈,，其原因也在于這些引起嗅覺器官反應(yīng)的物質(zhì)，不能很好地分配到所有嗅覺細胞上,。
How your nose is more complex than a 747
Study shows why you have to sniff deeply for subtle scents
Your nose may not be as big as a jumbo jet, or maybe it is — but whatever its size, your nose is more complex in one sense.
A new study of how air flows through your schnoz reveals the process to be more complicated than air coursing over a jet's wing.
The scientists figured this out by running water laced with colored beads through a model honker. Not a model's nose, but a 3-D nose model, one twice as big as lifesize. Anyway, these guys really nosed around.
This graphic traces air flow through a 3-D model of the nose, with the flow entering the nostril from the right.
"From quiet breathing to rapid sniffing, we want to know exactly what is happening," said Bob Schroter of the Imperial College London. The results clear some things up and could lead to new ways to clear up blocked nasal passages, the researchers say.
"The geometry of the nose is highly complex, with no straight lines or simple curves like an aircraft wing, and the regime of airflow is not simply laminar or turbulent," said Professor Denis Doorly, assuming laminar and turbulent are simple. (Laminar means smooth, and turbulent is, well, anything but.)
The study revealed why we have to inhale deeply sometimes to capture a subtle scent, perhaps that of a flower.
Smelling relies on getting air to the olfactory bulb, which sits somewhat inconveniently at the top of the nose, thought conveniently on the inside. The way the nose is built, you have to take in a sharp breath at high velocity to shoot faint smells up there. Something like a strong gust of wind instead of a gentle breeze. Then the nose takes over, the model showed: Its structure causes air to eddy around the bulb, lingering a bit so you can enjoy the scent, or not.
The model nose was built from transparent silicone, based on computerized scans "of anonymous patients found to be nasally healthy." The research beats examining cadavers, the scientist said. The findings could help surgeons plan nose jobs and allow drug companies to figure out better ways to get drugs straight into your bloodstream.
The research was announced Thursday and is detailed in the January issue of Business, a magazine put out by the Biotechnology and Biological Sciences Research Council.
