What are smells?
What makes the smell of something, like, say, rotten eggs? While what's making the smell may
be invisible to the naked eye, it doesn't mean there's nothing there! The smell is just made of
things too small to see. You know they're there because you can smell them.
Odors are tiny molecules of chemicals from things like food, or flowers or poop that float
through the air. Many odors aren't single scents or single kinds of molecules but a whole mixture
of them.
How do we smell smells?
Through your nose. It's a mucus-covered, twisty cavern that's built to smell as well as warm,
moisten, and filter the air you breath. When you breath through your nose, air enters both of your
nostrils. Hairs, hanging from the walls of each opening, act as filters trapping dirt, dust, pollen
-- all sorts of things -- even bugs!
As the air moves further back inside your nose, the locale gets warmer and slimier. There's
wet mucus everywhere! And if you look carefully, you discover the mucus is actually moving.
Incredibly, small hair-like structures called cilia are sweeping or undulating back and forth,
moving the mucus (and anything trapped in it) further and further back. At the same time, the air
moving back is warmed by blood vessels just beneath the surface, filled with warm, pulsing blood.
As the air spirals around, bouncing off ridges and valleys, the passageway opens up to a big
cavern -- your nasal cavity. Rivulets of mucus stream back and down into our throat. You swallow a
lot of it!
The odor chemicals that you inhaled, on the other hand, begin to float upward, not downward.
They hit a ceiling area in your nasal cavity. About the size of a postage stamp, it's covered with
millions upon millions of microscopic nerve cells that can detect smell. Odor molecules sink
through a thick, mustard-colored mucus until they reach the sensitive hair-like tops of the nerve
cells and get trapped. Differently shaped nerve cells recognize different smells because each smell
molecule fits into a nerve cell like a lock and key. Then, these cells send signals along your
olfactory nerve to the smell center in your brain. It senses the odor or collection of odors. Does
it smell bad or good? Now that all depends on you and your sense of smell.
What's the connection between smell and taste?
Most of your sense of taste is really about your sense of smell. Do you think that the
spaghetti and meatballs you're eating taste delicious? Much of the reason is because you like their
smell. In fact, you're doing a lot of sniffing. Not only are you smelling before you take a bite,
but while you are chewing, odor molecules from the ground-up food inside your mouth float upwards
taking that remarkable smell journey.
Factoids
- If your sniffer is in peak performance you can tell the difference between 4000-10,000 smells.
Now that's heavy-duty sniffing!
- WARNING: As you grow older, your sense of smell gets worse. Children are likely to have much
more subtle senses of smell than parents or grandparents.
- MAYBE YOU WANT TO BE BLOODHOUND? They smell at least 1000 times better than humans.
- MAYBE YOU WANT TO BE A MALE MOTH? Just a dozen odor molecules from a lady moth a block away
can drive a male moth crazy!
- BE GLAD YOU'RE NOT A DOLPHIN OR WHALE -- Instead of two nostrils in the middle of your face,
you'd have one blowhole on the top of your head!
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