We all cry. Whether we feel extreme sadness or intense joy, tears seem to come and sometimes we just cannot stop. Evolutionary biologists over the years have puzzled over the mystery of tears. What is the science behind crying? Three Types of Tears:
Basal tears: these are your normal tears. They lubricate and provide nourishment (water and nutrients) to your eyes, while also protecting it as a shield. They can also improve your vision and sharpen your focus. They contain oil, mucus, water, salt and some antibodies that help fight infection.
Reflex (aka irritant) tears: these tears help to flush away foreign irritants. They also contain more antibodies to fight bacteria.
Emotional (aka psychic) tears: they occur in response to biological, psychological, and sociological factors that cause strong emotions. Compared to other tears, they contain more stress hormones and painkillers. Research has shown that emotional tears have higher concentrations of protein-based hormones such as prolactin (promotes crying), adrenocorticotropic hormones (indicate high stress levels), and leucine-enkephalin (an endorphin that reduces pain and improves mood).
Three Layers of Tears:
Inner mucus layer: keeps the tear attached to the eye.
Watery middle layer: the thickest layer. It provides hydration, a barrier against bacteria, and protection for the cornea.
Outer oily layer: keeps the surface of the tear smooth so that the eye can see through and prevents evaporation.
How Do We Cry?
Lacrimal glands above each eye produce tears. Blinking causes tears to spread out across the surface of your eye, and they eventually drain out into puncta (tiny holes in the corners of your upper and lower eyelids). The tears sequentially travel through small canals and down a duct into your nose.
Gender and Crying
Although prolactin promotes crying, testosterone inhibits it. As a result, as children become adolescents, the amount of crying in boys declines considerably, while the opposite occurs in girls. Also, men have smaller tear ducts than women. Men cannot produce tears in the same volume and frequency as women can.
Abnormal Tearing
When tear ducts get blocked, the tears can’t drain and as a result the eyes overflow. Long-term abnormal tearing can lead to swollen, infected, or inflamed eyes. Abnormal tearing can be caused by dry eyes, aging, seasonal allergies, conjunctivitis, longtime use of eye drops, nasal or sinus conditions, structural blockage, tumors in the nose, and chemotherapy. Symptoms include watery eyes, blurred vision, eye discharge (eye drainage collects on the eyelids and eyelashes), and inflammation. Treatment options include eye drops, medications, flushing the tear duct, balloon catheter dilation, stenting, or dacryocystorhinostomy (surgery).
References
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Hoyt, Alia. "How Crying Works." HowStuffWorks, 9 June 2023,
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Mukamal, Reena. "Facts about Tears." Edited by David Turbert. American Academy of Ophthalmology, EyeSmart, 18 Apr. 2023, www.aao.org/eye-health/tips-prevention/facts-about-tears. Accessed 4 Nov. 2023.
"The Science Behind Why We Cry." Southwestern Eye Center, 26 Apr. 2019
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Stiles, Katie. "The Science of Tears." PsychCentral, psychcentral.com/blog/the-science-of-tears#what-are-tears. Accessed 4 Nov. 2023.
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