A big batch of cookies coming out of the oven. Your gym bag full of dirty
clothes. How do you smell these smells and thousands more? It's your nose, of
course.
Your nose lets you smell and it's a big part of why you are able to taste
things. The nose is also the main gate to the respiratory system, your body's
system for breathing. Let's be nosey and find out some more about the nose.
Nose Parts
The nose has two holes called
nostrils. The nostrils and the nasal passages are separated by a wall
called the septum (say: sep-tum). Deep inside your nose, close to
your skull, your septum is made of very thin pieces of bone.
Closer to the tip of your nose, the septum is made of cartilage (say:
kar-tul-ij), which is flexible material that's firmer than skin or
muscle. It's not as hard as bone, and if you push on the tip of your nose, you
can feel how wiggly it is.
Behind your nose, in the middle of your face, is a space called the nasal cavity. It
connects with the back of the throat. The nasal cavity is separated from the
inside of your mouth by the palate (roof of your mouth).
Getting the Air in There
When you inhale air
through your nostrils, the air enters the nasal passages and travels into your
nasal cavity. The air then passes down the back of your throat into the trachea
(or windpipe) on its way to the lungs.
Your
nose is also a two-way street. When you exhale the old air from your lungs, the
nose is the main way for the air to leave your body. But your nose is more than
a passageway for air. The nose also warms, moistens, and filters the air before
it goes to the lungs.
The inside of your nose is lined with a moist, thin layer of tissue called a
mucous membrane (say: myoo-kus mem-brayne). This membrane
warms up the air and moistens it. The mucous membrane makes mucus, that sticky
stuff in your nose you might call snot. Mucus captures dust, germs, and other
small particles that could irritate your lungs. If you look inside your nose,
you will also see hairs that can trap large particles, like dirt or pollen.
Further back in your nose are even smaller hairs called cilia that you can
see only with a microscope. The cilia move back and forth to move the mucus out
of the sinuses and back of the nose. Cilia can also be found lining the air
passages, where they help move mucus out of the lungs.
Sniff, Sniff, Take a Whiff
The nose allows you
to make scents of what's going on in the world around you. Just as your
eyes give you information by seeing
and your ears help you out by hearing, the
nose lets you figure out what's happening by smelling. It does this with help
from many parts hidden deep inside your nasal cavity and head.
Up on the roof of the nasal cavity (the space behind your nose) is the
olfactory epithelium (say: al-fak-tuh-ree
eh-puh-thee-lee-um). Olfactory is a fancy word that has to do with
smelling. The olfactory epithelium contains special receptors that are sensitive
to odor molecules that travel through the air.
These receptors are very small - there are at least 10 million of them in
your nose! There are hundreds of different odor receptors, each with the ability
to sense certain odor molecules. Research has shown that an odor can stimulate
several different kinds of receptors. The brain interprets the combination of
receptors to recognize any one of about 10,000 different smells.
When the smell receptors are stimulated, signals travel along the
olfactory nerve to the olfactory bulb. The olfactory bulb is
underneath the front of your brain just above the
nasal cavity. Signals are sent from the olfactory bulb to other parts of the
brain to be interpreted as a smell you may recognize, like apple pie fresh from
the oven. Yum!
Identifying smells is your brain's way of telling you about your environment.
Have you ever smelled your toast burning? In an instant, your brain interpreted
the smell and a problem and you knew to check on your toast.
You learned to associate a certain smell with burning and now your brain
remembers that smell so you recognize it. Your sense of smell also can help you
keep safe. For example, it can be warn you not to eat something that smells
rotten or help you detect smoke before you see a fire.
Tastes Great!
Most people just think of the tongue when they think about
taste. But you couldn't taste anything without some help from the nose! The
ability to smell and taste go together because odors from foods allow us to
taste more fully.
Take a bite of food and think about how it tastes. Then, pinch your nose and
take another bite. Notice the difference? It's just another reason to appreciate
your knockout of a nose!
Updated and reviewed by: Mary L. Gavin,
MD
Date reviewed: July 2004
Originally reviewed by: Steven P. Cook,
MD