Object lesson No 75

5th October 2001 at 01:00
Is yours aquiline or hooked? Retrousse or Roman or just plain ridiculous? Cyrano de Bergerac, hero of the play by Edmond Rostand, knew the importance of the shape of one's breathing apparatus. Today, the 17th-century cavalier would set aside his poetry and get a nose job.

Such nasal reshaping is formally known as rhinoplasty, and the term "rhino" comes from the Greek. A rhinoceros is a nose with horn. (OK, it's also a bloody big animal.) A rhinologist studies people's conks and her favourite tool is a rhinoscope.

So let's pick up our rhinoscopes and take a trip up a nostril. Push past the hairs that guard the entrance and filter out the biggest dirt particles. It's really not that revolting. In fact, if you put aside squeamishness, you'll realise that the nose is an impressive device - one that can teach office air-conditioning systems a thing or two. It cleans, warms and moistens the air we breathe and houses the olfactory organ which sniffs out roast dinners and the proximity of municipal loos.

Once through the hair, the complex nasal cavity is revealed. Its roof is formed by the bones of the skull, the walls by the upper jaw, and the floor by the hard palate that separates the nose from the mouth. Further back, the soft palate closes off the throat to prevent food going into the nose instead of the stomach.

Along each nostril's outer walls run three "conchae". These are thin plates of bone covered with a mucous membrane and they massively increase the nasal work surface. Equipped with fine hairs called cilia, the membrane collects the daily grime of bacteria, dust, carbon and soot.

What looks like the cross-section of a rope hangs down at the back of the nose. This bundle of fibres connects to the olfactory nerve, which sends smell signals to the brain. Tiny particles dissolve in the liquid coating the fibres, a process that stimulates the nerve. Quite how it works is uncertain, but it seems that a molecule of smelly stuff "fits" with a dedicated receptor cell on the fibres. For example, one receptor will warm to an unpasturised Brie, while another may thrill to a delicate Wensleydale.

But the next time you slice yourself some Stinking Bishop cheese, remember that a mere four molecules can trigger a reaction. Pooh!

Stephanie Northen

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