In this article, we take a journey through the human body with a magnifying glass, discovering the hidden world. Tears. What are those tiny droplets for? Why are they salty? How many litres do we produce in a year? Let's find out together!
The eye, also known as the eyeball, is a jellyball made up of 98% water.
It is one of the most fragile organs of the human body and therefore needs constant protection and hydration. But don't worry, tears will come to the rescue!
What are tears made of?
Contrary to what it may seem, they are not just made up of water, but also of other very important substances, including proteins, lipids (fats), mineral salts and bactericidal substances that can protect the eye from infections.
Their path: from the eyes to the nose
Tears are produced by the lacrimal glands, structures hidden behind the eyelids, in the upper part of the eye sockets (the hollows of the skull bones where the eyes are located).
Once developed, they are distributed over the entire surface of the eye while constantly opening and closing the eyelids.
They are then gradually expelled through the lacrimal duct, a small tube located in the inner corner of the eye, which ends in a structure called the lacrimal sac, from where the tears enter the nasal cavity.
That's why we have to blow our nose and use thousands of tissues when we cry: because of that connection between our eyes and nose!
Are all tears the same?
Scientists divide them into three types: basal, reflexive and emotional.
Basal tears are those that normally cover the surface of the eye, creating a tear film (a thin protective layer that separates the eye from the outside environment).
Reflex tears are tears that are secreted in large quantities when threatened, such as irritation from dust, pollen or sand blown in by the wind.
Emotional tears are an expression of our emotions, whether it is joy at receiving good news, excitement at watching a movie with a happy ending or sadness.
What are the benefits of tears?
They are indispensable for the good health of our eyes and our vision. They lubricate our eyes, protect them from external threats and keep our vision clear.
In fact, like car windscreen wipers, the constant opening and closing of the eyelids allows tears to spread throughout the ocular surface and sweep away dust, germs and debris, preserving visual acuity.
Without this mechanism, layers of dust would build up on your eyes and your vision would deteriorate!
What's more, we would be constantly exposed to infections!
In fact, as mentioned earlier, tears have antimicrobial enzymes, i.e. special proteins that can defeat external germs such as viruses, fungi and bacteria that threaten the health of our eyes. This defence system is called lysozyme.
Why are the tears salty?
Everyone has, at least once, had to taste the tears that came to their mouths after crying heavily.
You've probably noticed that, although they consist mainly of water, they're not tasteless, but salty.
This is because they contain a special mineral salt, sodium chloride, simply called salt!
How many tears do we produce in a year?
Now that we understand what it is, let's get to the numbers! How many tears do we produce in a year? And in a lifetime? It's not easy to calculate, it certainly depends on how tearful a person is... but an American study estimates that the average person produces between 60 and 110 litres of tears a year (almost as many as a bathtub). So we produce between 5,000 and 9,000 litres in a lifetime!
Why do we cry when we feel anger and frustration?
To answer this question, it is first important to know what happens in our bodies during anger. When a person gets angry, the central nervous system immediately puts our body on alert, triggering a series of physical reactions. Our pupils dilate, cortisol - the stress hormone - is released, our heartbeat and breathing speeds up and blood flow rushes to our muscles, leaving them tense.
This mechanism is instinctive. It comes from prehistoric times, when every sign of threat was followed by a reaction that forced us to be ready to fight for survival.
In many cases, the level of stress caused by anger is so great that we are unable to return to a rational state and explain in words how we feel. That is why we cry. Crying in situations of anger serves, among other things, to reduce tension.
According to cognitive behavioural therapy psychologists, tears - those evoked by a wide range of emotions, including anger - arise in response to an intense experience, but may also have a more complex purpose. They suggest that crying is a form of non-verbal communication that serves to let the other person know that they have gone too far: thus, it serves to elicit empathy or gain support.
Tears also contain enkephalin-leucine, a natural analgesic that is secreted during crying. This is why we feel better after we cry.
And finally... is it true that onions make you cry?
Yes! Cutting onions is one of the most effective ways to cry more tears and break the record of 9,000 litres!
This is because onions contain special irritants, including sulphuric acids, which evaporate as tear gas and irritate our eyes, stimulating reflexive lacrimation.