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Which one is your favorite smell? Is it the smell of flowers, eggs and bacon cooking or fresh coffee? Whichever it is, you can detect it thanks to your sense of smell. Learn more about this sense and the mechanisms our body uses to identify odors.

Experiencing sensations

Do you have a favorite ice-cream flavor? Which one is it? Does it smell sweet? What about that feeling when you burn your hand with the iron? Is it painful or what? Can you describe the different sensations that you get in these two situations?

Thanks to our five senses we are able to experience these sensations and many more. Our senses are designed for us to enjoy from everything that surrounds us but also to keep us alert and safe. We use them all the time without being fully aware of how important they are. 

Sniff, sniff

Here we will talk about olfaction, or the sense of smell.

Together with the sense of taste, it is classified as a chemical sense, because it relies on the detection of chemicals that detach from any object and dissolve into the air.

The sense of smell is quite complex. If you remember, our tongue, or more specifically our tastebuds, can detect up to four different tastes. It is not like that with the nose.  Just recently, scientists from the Rockefeller’s Laboratory of Neurogenetics and Behavior calculated that humans can detect around three trillion odor mixes. Can you imagine that?

Of course, this amazing yet complex job couldn’t be performed only by our nose and its structures. When we smell,  both our nose and brain work as a team to detect, process and send back messages, so that we know the difference between the smell of smoke coming from a fire from the smell of smoke from a cigar.

The process of smelling

When we inhale air into our lungs we are taking oxygen in, to keep us alive, but we also take small odor particles that come from everything that surrounds us.

When these particles reach the inside of the nose, they stick between a layer of mucus and another layer that is known as the olfactory epithelium.
The epithelium is formed by hair cells that actually got hairs on their surface, properly known as cilia. These hairs are in direct contact with the odor particles present in the air. From the other side of the epithelium cells, nerve fibers come out to connect this region of the nose with our brain.

When an odor molecule reaches the olfactory epithelium, it gets in contact with the cilia and switches on a signal that travels from the cilia to the other side of the hair cells, through the nerve fibers, until it reaches the olfactory bulb. The olfactory bulb has connections that send the odor signal to specific parts of the brain, mainly to the olfactory cortex, the hippocampus, the amygdala and the hypothalamus.

Is in these regions were the information is processed and codified to finally let us know what exactly we are smelling at that particular moment. 

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