Your nose and smell

The most important function our nose has is to help us breathe.  Have a look at the diagram or in a mirror and you will see that your nose has two holes at the end – the nostrils.  The nostrils lead to the nasal passages that are separated by a very thin wall of cartilage called the septum.  Cartilage is quite flexible but not as strong as bone, which is why you can wiggle the end of your nose! 

As the septum gets closer to your skull, the cartilage is replaced by very thin layers of bone that make up the bridge of your nose.  The bridge of your nose is much stronger than the tip and you cannot wiggle it around!  

The nasal cavity is behind your nose, right in the middle of your face but hidden.  It is connected with the back of your throat and separated from the inside of your mouth by your upper palate (that is, the roof of your mouth).  Behind the nasal cavity, the adenoids are small bundles of cells that fight microbes that you sometimes inhale and keep you healthy.

Inside your nose is quite moist most of the time.  This is due to a very thin layer of membrane called the mucous membrane.  The mucous membrane does two different jobs.  Firstly, it moistens and warms up the air so it isn’t too cold when it gets to the lungs!  More importantly, it also makes gooey, sticky mucus.  This helps to keep you healthy by working with your nasal hairs to trap dust, microbes and all kinds of small things like pollen that float in the air and can make us sick.  At the very back of your nose, tiny hairs called cilia move back and forth to move the mucus from the sinuses where it is produced and into the nose where it does its work. 

If something gets up your nose that doesn’t belong there it can make you sneeze!  The sneeze helps to keep you healthy by trying to shoot out anything that doesn’t belong at almost 100 miles an hour!!  This is why you need to cover your nose and mouth when you sneeze as the germs and microbes you get rid of should go into your hankie rather than the air your friends are breathing!

Your nose is the main olfactory organ – that is, the organ that allows you to smell.  To do this it needs help from other parts of the olfactory system. 

In the roof of the nasal cavity (the space is behind your nose, right in the middle of your face), the olfactory epithelium (that is, the area of skin that allows you smell) has tiny receptors that can recognize different smells that are in the air around us.  There are at least 10 million receptors in your nose!!  Between them, these receptors can recognise about 10,000 different types of smells – some of them good and some of them very bad!

When your smell receptors come into contact with a smell, they signal the olfactory bulb, which is near the nasal cavity.  Signals are sent to the brain and you can then tell what the smell is.  If the smell is good, like your favourite dinner, then you know you have something to look forward to!  If the smell is bad, it can keep you safe by making sure you don’t eat rotten food.  It may also signal danger, like a smell of burning, which gives you a warning that you may be in a dangerous area.

Did you know..?

Believe it or not, your sense of smell helps you to recognise tastes!  It works with the tongue to allow us to get the full flavour and taste of food and drinks.  Your sense of smell is over 10,000 times more sensitive than your sense of taste!

Smells help train your brain – when you smell something for the first time, your brain remembers it when you smell it again.  This memory is linked to the part of your brain that controls emotions.  So, if you are happy or sad when you eat or drink something, you may feel happy or sad when you eat or drink it again!

The same type of cilia that you have in your nose can also be found in your lungs!  These cilia move back and forth, like in your nose to help to keep your lungs clear of mucus.  Your lungs have mucus to catch any microbes that could make you sick!