The smell is the first sense we use when we are born. All throughout our lives, we learn to distinguish all kinds of smells, up to 10,000 different ones, the specialists say. How do we do that? We’ve got help from our 12 million olfactory receptor cells. Nevertheless, our 12 million is nothing compared to a dog’s 100-200 million olfactory receptor cells which enable them to distinguish as much as 40,000 different odors. But you don’t need to feel bad about that. Our noses are already incredible and we had known almost nothing about it, until 2004 when some awesome Nobel Prize winners took a chance at unscrambling our sense of smell. So, what do we know now of how smell works?
How does smell work?
Smell works with our noses sniffing different molecules from the air and letting them find their way around our nostrils. Our nostrils filter and analyze the air and molecules and then let them get to our lungs. Nevertheless, at the back of our noses, there is a little wizard called the olfactory epithelium. Basically, it’s just a patch of skin, but it’s got “special powers” called olfactory receptor cells which can sense smells much like our taste buds sense taste. The molecules we inspire get stuck on the mucus which covers our olfactory receptor cells. They cannot escape it and start to dissolve until they can be carried away by the olfactory receptor cells to the olfactory tract and then to our brain.
This olfactory epithelium is the “big boss” here, like the brain of the smell and its size can determine how good an animal’s sense of smell is. For example, dogs have olfactory epitheliums that are 20 times bigger than ours. How about that? I guess it doesn’t come as a surprise since it’s a general-known fact that dogs can recognize so many odors, much more than us humans.
How does smell travel?
Smells travel through the air through a process called diffusion. Air particles, and the odor particles within the air, move freely in all directions. It follows a random movement in the direction of the concentration gradient (from most concentrated to least concentrated areas).
There are still a lot of “smelly” things to be researched.
It was the year 1991 when a team of researchers from Howard Hughes Medical Institute and Fred Hutchinson Cancer Research Center discovered that there are about 1,000 genes responsible for our olfactory receptors. They also noticed that a single receptor is responsible for certain kinds of smells. So, it’s like a team of receptors there, each specialized on a limited number of smells. The smell is a team effort? Might be, why not? Still, there are a lot of other things about the smell that we do not know yet. For instance, our olfactory epithelium is pigmented and we don’t know why, yet.
Let’s talk about our brain’s 40 million different olfactory neurons now!
Okay, so we know how our nose works, how the air and molecules in the year get turned into smell. Still, how does our brain differentiate between the tons of different smells out there? It seems this 40 million different olfactory neurons help. They are always on guard to read different kinds of smells and one or more of them are triggered by a certain kind of odor. They combine and share their “workload” and thus you distinguish an extensive bunch of smells.
Nevertheless, there is a reason why they’re always so active. They are the only neurons in our body that get changed every four to eight weeks.
Our sense of smell is quite important to us. Since it was the first sense we’ve ever developed, it’s got a direct link to our brain, while sight or sound first go to a relay center in our cerebral hemisphere, where they are filtered and then transported to different corners of the brain. So, maybe next time you trust your smell more!
List of Smells
There are 10 basic smells that are well researched and documented:
- Fragrant (e.g. florals and perfumes)
- Fruity (all non-citrus fruits)
- Citrus (e.g. lemon, lime, orange)
- Woody and resinous (e.g. pine or fresh cut grass)
- Chemical (e.g. ammonia, bleach)
- Sweet (e.g. chocolate, vanilla, caramel)
- Minty and peppermint (e.g. eucalyptus and camphor)
- Toasted and nutty (e.g popcorn, peanut butter, almonds)
- Pungent (e.g. blue cheese, cigar smoke)
- Decayed (e.g. rotting meat, sour milk)
We don’t smell the same things.
The truth is, we don’t smell the same things. There is a famous example with asparagus. The researches have shown that only a quarter of the population can record the specific odor that urine has after eating asparagus. The other 75% of people do not feel it. So, yes, we’re different when it comes to smell as we’re different in a lot of other aspects in life. The important thing is to learn to trust your smell because sometimes it can tell you more than you’ve expected. And now that you’ve learned how smell works, it will be much easier to trust it, right?