We did it the day we were born, but also the day we were sad for some reason. It happened to us when we felt the greatest joy of our life, but also the worst day of our life. I’m talking about crying. But what’s the use of crying? How do tears “work”?
What is crying and when and why does it occur?
By “crying” we commonly mean the act of producing and releasing tears in response to intense emotion or stress. However, situations of “crying without tears” and also “tears without crying” can occur. In infants, for example, given the immaturity of the tear duct, a typical crying without tears can occur. In adults, however, “tears without tears” can occur in at least between situations:
1) eye contact with foreign bodies (midges, dust) or various irritants (typical is the cry from contact with the organic sulphides contained in the onion) cause squeezing of the tear gland in the absence of a related emotion;
2)innervation of the lacrimal gland by secretagogue neurons directed primarily to the salivary glands (the ” crocodile cry “);
3) rice can make you water. Laughing intensely determines a strong muscle activation in the face and this can stimulate the tear glands up to ” cry with laughter “. you cry for happiness? Why do we cry for joy and pain?
When you feel a strong emotion, the limbic system of the brain stimulates the central nervous system, which in turn sets in motion a series of physiological reactions: the heartbeat increases, the rhythm of breathing changes and the tear glands, placed above the upper arch of the eye, produce tears. When you cry, the liquid “flows” into the corner of the eye and flows along the conjunctiva, the membrane that lines the inside of the eyelids, ending up in the nasal cavity. With each blink of the eye the eye lubricates. This avoids the dehydration of the bulb and facilitates the removal of the dust.
What are tears made of, what are they for and where are they produced?
What are tears produced from?
The tear (or tear film) is a liquid structure that physiologically covers the bulbar eyelid conjunctiva and the cornea and is produced by the tear apparatus. This apparatus, as you can guess from the photo, is made up of two parts:
1) secretory portion (lacrimal gland and secretory ducts) which secretes the tear,
2) excretory portion which has the task of draining the tear towards the nose (tear sac) , channels and ducts).
What are tears used for?
The main functions of the tear film are five:
1) Cleaning : through the tear film the impurities coming from the external environment flow towards the excretory component of the tear glands.
2) Lubrication : the mucotic component of the tear film performs a lubricating function, towards the corneal epithelium.
3) Nutrition : the aqueous component of the tear film acts as a vehicle for numerous substances dissolved in the tear; oxygen, ions, carbon dioxide, mucins, lipids; essential substances for the eutrophism of the ocular surface and its nutrition.
4) Optical transparency: the mucous layer of the tear film improves the optical transparency of the corneal surface. The microvilli of the corneal epithelium act as a basis for the mucin, which is absorbed by the corneal villosity, allowing a better surface uniformity.
5) Defense : the tear film represents the main defense against corneal and conjunctival bacterial infections, together with the eyelid. Spreading evenly over the corneal epithelium, it acts as a protective barrier to external bacterial agents and has a powerful disinfectant power.
What are tears made of?
Tears are made up of 98% water, the remaining 2% is mainly composed of electrolytes, numerous proteins (albumin, lactoferrin, immunoglobulins …) and glucose. The disinfectant power mentioned above is due to various tear components: sodium chloride, urea and a bactericidal enzyme, lysozyme . Not all tears are the same: those produced during emotional crying (from joy or sadness) have a different chemical composition from other types of tears: in fact they contain a significantly higher amount of prolactin hormones, adrenocorticotropic hormones, leu-encephalin (an endogenous opioid and powerful anesthetic), potassium and manganese.
Do animals cry?
It is believed that no other living being besides man can produce tears in response to different emotional states, although this is not entirely correct for different scientists.
Female tears lower testosterone
Before closing, a curiosity: female tears contain substances capable of reducing male sexual arousal and the production of testosterone, the hormone responsible for desire and aggression. Female tears contain substances capable of reducing male sexual arousal and the production of testosterone, the hormone responsible for desire and aggression. This was demonstrated by an experiment by the Weizman Institute in Rehovot (Israel), in which some male volunteers were asked to distinguish with a sense of smell a handkerchief soaked in tears and one soaked in saline. They did not succeed, but after sniffing the tears they were less attracted to photographs and videos of women, and in their saliva testosterone levels were reduced. Functional magnetic resonance imaging then showed less activity in the brain area associated with sexual desire. From an evolutionary point of view, therefore, women would resort to crying to keep male desire under control and, in particular,