Although we are not required to learn about the senses incluidng the sense of smell a for the ITEC Certificate in Anatomy, Physiology and Pathology, it is an interesting subject.
One of the commonly-known symptoms of the COVID-19 virus is the change or loss of taste and smell. It’s possible that we give these senses very little regard, (until we lose them, that is). As we know when we have a blocked up nose, taste relies on smell, so how powerful a sense is it?
We taste food and drink thanks to taste buds present on our tongues.
There are five modalities of taste: Sweet, Sour, Bitter, Salty and Umami (think the savoury flavour of soy sauce, mushrooms, seaweed, etc).
Many of us might consider our ability to taste things as being quite sophisticated, so what about our sense of smell?
Olfaction is the perception of odours; our sense of smell. We have two distinct modes of olfaction - orthonasal and retronasal.
Orthonasal olfaction is what happens when we sniff. Odour molecules are drawn into the nasal cavity as we breathe in air. The top of the nasal cavity is lined with olfactory epithelium, a mucus membrane, which traps and dissolves odour molecules. Olfactory receptors are stimulated by these molecules and their linked sensory neurons send messages directly to the brain.
Retronasal olfaction is what happens when we chew food or take a drink. The odour molecules travel up from the back of the mouth to the olfactory receptors. These, combined with messages from our taste buds, give us the perception of flavour.
With the exception of people who are anosmic, (having no sense of smell), it has been suggested in a 2014 study that we humans can smell up to one trillion different odours. One trillion. That is a million million. This, despite being considered less developed in olfaction than other animals.
By means of comparison, the human eye can distinguish up to 10 million different colours.
In everyday terms, this means that our sense of smell is an awesome asset.
That being said, we can’t necessarily identify one trillion different scents, but we have the potential to distinguish different odours.
Identifying odours takes training, as evidenced by the ‘Noses’ in the perfume industry. These individuals have a heightened sense of smell which they have developed through extensive olfactory training.
So how many smells can we actually identify? There is no one answer to this as identification relies on an individual’s experiences, olfaction and brain memory capacity. A popular number often quoted is that humans are able to remember 50,000 odours.
Even if that is a conservative figure, our olfaction must surely be considered a superpower
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