Science Focus - the home of BBC Science Focus Magazine
If we only have one trachea, why do we have two nostrils? © Getty Images

If we only have one trachea, why do we have two nostrils?

Subscribe to BBC Science Focus Magazine and get 6 issues for just £9.99

Two eyes, two ears, two nostrils - makes sense, right?!

Asked by: Steve Purves, Preston

Advertisement

Two eyes, two ears, two nostrils. We need our doubles for stereoscopic vision, stereo sound, and super smelling. Our nostrils are separated by a septum, in effect giving us two noses. Most of the time, one nostril allows less air to pass through than the other, with the nasal flow switching every few hours. The slower airflow is caused by the tissue inside swelling with increased blood flow.

We smell using sensory cells high up in the nose, and some odour chemicals need more time than others to bind to these receptors. So a low-airflow nostril gives slow-acting odours more time to be detected, giving us a greater range of smell.


Advertisement

Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun facts.

Authors

Dr Emma Davies is a science writer and editor with a PhD in food chemistry from the University of Leeds. She writes about all aspects of chemistry, from food and the environment to toxicology and regulatory science.

Advertisement
Advertisement
Advertisement

Sponsored content