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Getting the Air in There
The nose is
necessary: it's the main airway to your respiratory system. When you
inhale air through your nostrils, the air enters your nasal cavity and
travels along the top of your palate (say: pal-it). (Your
palate is the wall that separates your nose from your mouth, sometimes
called the roof of your mouth. You can check out its surface by lifting up
your tongue and using it to feel around.) The air then passes through your
mouth and throat and soon ends up in the lungs. When your lungs are ready
to exhale the old air, the nose is the main way for the air to leave your
body. 
But your nose doesn't just take air in and send it along to the lungs -
it warms, humidifies, and filters it first (humidifying means adding
moisture). The inside of your nose is lined with a mucous membrane
(say: myoo-kuss mem-brane), which is a wet, thin layer of
tissue. This membrane warms up the air on its way in and moistens it a lot
- in fact, air that's come in through the nose reaches almost 75%
humidity!
The nose knows how to filter things out of the air before they make
their way into your throat. On the inside front surface of the nose are
tiny protective hairs that catch dust and other irritants that would be
harmful if they were inhaled. And some irritants that do get caught
in there are so irritating that your nose wants to get rid of them right
away - by sneezing! Sneezing is an involuntary
way of removing an irritation from your nose. Your brain, muscles, and
nose all work together to send those particles flying out of your nose,
sometimes at speeds of up to 100 miles an hour. Now that's a speedy
sneeze! And on each side of the upper part of the throat, behind the nasal
cavity, are adenoids (say: ad-eh-noyds). These are bunches
of tissue that contain cells that help fight off any germs that you may
have inhaled.
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