January 6, 2005 | David F. Coppedge

Why You Breathe Deep to Sniff a Flower

It may sound like a 747 when your uncle blows his nose, but scientists at Imperial College found nose airflow to be more complicated than the aerodynamics of a jumbo jet’s wing, according to a press release by the reporting the Biotechnology and Biological Sciences Research Council .  They made a 3D model of the nasal passages and studied colored liquid and beads as they flowed through.  The press release comments, “The fluid dynamics of the nose is one of the most complex in the body, even more so than the flow of blood through the heart, with anatomical structures that cause eddies, whirls and recirculation.”

Dr Denis Doorly, the other principal researcher [with Bob Schroter], said, “People are used to the flows around an aeroplane being complicated but that is in some ways simpler than understanding the flows inside the nose.  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.”   (Emphasis added in all quotes.)

This leads to the answer to the question posed by the title of this entry:

The research has mapped the flow of air around anatomical landmarks in the nose, such as the conchae and has discovered why we need to breathe deeply to smell a flower.  Our sense of smell relies on a sample of air reaching the olfactory bulb at the top of the nose and that requires a sharp breathe [sic] and a high velocity shot of air to reach it.  The Imperial scientists have found that the geometry of the nose causes the air to eddy around in the vicinity of the bulb so you can smell the flower.

One of the results of the study may be to design better ways to unblock a stuffy nose.  Come to think of it, the sneeze response is usually pretty effective, and pretty amazing, too.  It involves coordination between the lungs, the eyes, the brain, the nose and the diaphragm.

Sniffing must be true for all mammals.  Watch your dog sniff in puffs of air when trying to smell an object.  If the olfactory bulb were always exposed to every breath, it might overwhelm the brain with TMI (too much information).  This way, it allows the user to focus on a smell when it wants to.  So not only is the olfactory bulb offset from the breathing passage, it sits where the air forms an eddy, allowing it to get multiple readings for higher resolution.  Remember the 11/07/2001 headline, also, that reported you have a code in your nose.  Who designed the fluid dynamics of this system?  Charlie?  Eheu! (see 10/10/2002 headline).

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Categories: Human Body

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