A happy ending to a story, a sad break-up, an onion chopped into pieces—they all can trigger your tears.
Tears serve many purposes, and your eyes produce them all the time. In fact, you make 15 to 30 gallons of tears each year.
Tears are essential to help you see clearly and maintain the health of your eyes. They can also help communicate your emotions. Your body makes three types of tears.
Basal tears are in your eyes all the time to lubricate, nourish and protect your cornea. Basal tears act as a constant shield between the eye and the rest of the world, keeping dirt and debris away.
Reflex tears are formed when your eyes need to wash away harmful irritants, such as smoke, foreign bodies or onion fumes. Your eyes release them in larger amounts than basal tears, and they may contain more antibodies to help fight bacteria.
Emotional tears are produced in response to joy, sadness, fear and other emotional states. Some scientists have proposed that emotional tears contain additional hormones and proteins not present in basal or reflex tears.
Tears are not just saline. They have a similar structure to saliva and contain enzymes, lipids, metabolites and electrolytes.
Each tear has three layers:
1. An inner mucus layer that keeps the whole tear fastened to the eye.
2. A watery middle layer (the thickest layer) to keep the eye hydrated, repel bacteria and protect the cornea.
3. An outer oily layer to keep the surface of the tear smooth for the eye to see through, and to prevent the other layers from evaporating.
Lacrimal glands above each eye produce your tears. As you blink, tears spread across the surface of the eye. Then the tears drain into puncta, tiny holes in the corners of your upper and lower eyelids. Your tears then travel through small canals in the lids and down a duct before emptying into your nose. There, tears will either evaporate or be reabsorbed.
Sometimes babies are born with a blocked tear duct, a condition that usually resolves on its own. An eye infection, swelling, injury or a tumor can cause a blocked tear duct in adults. When a lot of emotional or reflex tears are made, they overwhelm the lacrimal drainage system. That’s why these tears can spill out of your eyes, run down your cheeks and sometimes dribble out of your nose.
Basal tear production slows with age, and this can lead to the development of dry eye. Dry eye is a common problem for people undergoing hormonal changes, especially women during pregnancy and menopause. Contact lenses and certain medications can also cause dry eye. If you have dry eye, you may also be prone to blepharitis, a common cause of irritation or swelling of the eyelids. In addition to seeing an ophthalmologist, there are many simple things you can do at home to keep your eyes moist.
Why do we cry? Scientists have been trying to answer this question for centuries. In 1662, Danish scientist Niels Stensen discovered that tears originate in the lacrimal gland. We have three distinct types of tears: basal tears, reflex tears and emotional tears. Most researchers believe that emotional tears—triggered by strong feelings such as joy and sadness—are unique to humans. While there is a lot of crying research currently underway, we know that emotional tears are influenced by biological, psychological, and social factors.
Charles Darwin once declared emotional tears “purposeless,” but since then we have learned that tears facilitate social bonding and promote helpful behavior.
Psychologists believe that crying evolved from animal vocalizations. Infants and babies who do not have fully developed lacrimal glands can’t produce visible tears, but still cry audibly to solicit care and assistance. Through childhood and early adolescence, physical pain is also a common trigger for emotional tears, which tends to decrease with age.
As we age into adulthood, emotional tears are increasingly triggered by a broader range of feelings including: physical pain; attachment-related pain; empathic, compassionate pain; societal pain and sentimental or moral feelings.
“The value of crying may be more about the social response it prompts than its physiological effects,” says Lauren Bylsma, PhD, University of Pittsburgh. Dr. Bylsma has conducted multiple studies on crying and found that people were more likely to feel better after crying if they received social support during their tears. Tears that led to a resolution of the tear-inducing event or gave the cryer a new understanding of what was wrong helped the individual feel better. In contrast, people who tried to hold back their tears or cried in a non-supportive social setting (at work, for example) were less likely to feel better after crying.
While crying frequency varies significantly across individuals, Dr. Bylsma says it’s well established that women cry about three to four times more frequently than men, and when they do cry it tends to be more intense.
When your body makes emotional tears, your limbic system (the part of your brain associated with emotional arousal) signals your Pons (the brain’s “message station”), which then relays a signal to your lacrimal system to produce tears. More research is needed to understand the physiological and neural changes that come together with emotional tears.
While we know that all tears contain enzymes, lipids, metabolites and electrolytes, we have more to learn about the chemistry of emotional tears. Some scientists have proposed that these tears contain additional proteins and hormones not found in basal or reflex tears. Higher levels of prolactin, adrenocorticotropic hormone, Leu-enkephalin, potassium and manganese have all been located in emotional tears. Some researchers have hypothesized that the release of stress hormones like leu-enkephalin may help regulate the body or bring it back to a homeostatic level. However, these preliminary findings still need further scientific replication. Tears do much more than just moisten and protect our eyes from bacteria—just how much more we are still learning.
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