Appliance of Science: Why do we sneeze?

WE SPENT the bank holiday weekend catching up with family which was lovely. Of course, when you put a load of kids together, the questions really ratchet up; we were bombarded with them the entire weekend. My favourite one was…

DO ELEPHANTS SNEEZE?

The answer is, yes they do, through their trunks.

Elephants use their trunks in lots of different ways… they breathe through them, suck water up with them, smell with them and touch and grip with them; despite all these abilities, an elephant’s trunk is still it’s nose so sometimes it does indeed… sneeze through it.

An elephant’s trunk can grow to well over 1m in length and is a very strong yet dexterous organ. They have two nostrils running the length of their trunks with more than 150,000 muscle units.

An elephant can use its trunk to suck up as much as seven litres of water in one go. They also use their trunks to smell, in fact they have a better sense of smell than dogs do. Equipped with millions of olfactory receptor cells, elephants are thought to be able to smell water from many kilometres away.

What is most amazing about elephants’ trunks is that they can use them to hear, in a sense; they are sensitive to all kinds of vibrations, including sound vibrations and can detect rumblings travelling through the ground, from far off herds.

Appliance of Science: Why do we sneeze?

WHY DO WE SNEEZE?

Usually, we sneeze in response to an irritant detected in the lining of the nose or respiratory tract.

We are constantly breathing in foreign particles that the body can clear itself. There are tiny hairs, called cilia that line the nose and respiratory passages. The particles can irritate these linings, triggering a nerve response that makes the cilia move in a wave-like fashion to clear the particle.

Sometimes this movement of the cilia is not enough to remove the irritant and we need to up the response. We move on to the sneeze reflex, that expels the irritant and relieves the symptoms and potential threat. The irritant stimulates a nerve response that travels to the brain and triggers a reflex response.

The high velocity of expelled air achieved in a sneeze is due to a build-up of pressure inside the chest, while the vocal chords are closed. Once the pressure is sufficient the vocal chords open suddenly, allowing the pressurised air to flow through the respiratory tract, removing the irritant as it is expelled.

Studies also suggest that sneezing causes cilia to move at a much faster rate, for a minute or so after the sneeze. Elephants have less cilia in their nasal passages than we do, and are less sensitive, in general to minor foreign particles. So they tend to sneeze less often than us humans.

DO ALL ANIMALS SNEEZE?

No, it seems not all animals do, at least not in a traditional sense. Sneezing can really only occur in animals that have lungs and a respiratory tract. That rules out fish and insects for a start. Fish get their oxygen through their gills, insects breathe through holes in their abdomens, called spiracles.

They may have their own methods of clearing obstructions from their bodies but it would not be classified as a sneeze.

Naomi is a science communicator and mother to three inquisitive children. She can be found at sciencewows.ie

Feel free to email your questions to drhowsciencewows@gmail.com


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