Why Do People Cry?

From stubbing toes to witnessing the superiority of Fight Club, people are prone to shed a tear every once in a while.

You've seen it all too often. Three seconds left in the big game. Your team is down and the play of the century is about to unfold, one to be used in epic boasts in bars for years to come. You were there, about to witness…and then boom! More quickly than Madden can deliver a blindingly obvious line, the wife pulls the plug and nags you to do chores.

A man weeps for times past of a bachelor's life.

Of all animals, humans display a very unique range of emotion. While animals have the ability to produce tears, some aspects of crying may be unique to humans. Though the scientific study of crying still leaves many things unanswered and is quite complex, there are some basics and cool things to know on the subject.

In Soviet Russia, Tears Cry You!

Imagine taking a nice, long yawn. The simple mention of the yawn, and the mental image of taking a nice gulp of air, may have triggered you to actually yawn along with anyone sitting around you.

Though scientists feel that yawning may have both physiological and evolutionary aspects, as we yawn even before birth, there is an enigmatic behavioral aspect to the process. A similar perspective is given to aspects of crying.

We are naturally equipped to cry and produce tears. Tears are produced by the lacrimal gland, which is located in the outer, upper portion of each of your eyes. Upon release tears flow down the ocular surface of your eye and on to your tear ducts and nasolacrimal ducts. If you are sitting at a Kevin Federline and Shaquille O'Neill singing hour, your emotional tears will overwhelm your ducts and tears will flow down your cheek.

What's The Point Of Tears?

The tears of villainy produced by a mocking Sean Connery cutting into the brigand Trebek about his mother are not the same, as say, the tears shed by a Susy Homemaker who is cutting into onions to place on her Garden Burger. Though the ethics of a villain and those who put vegetables on a veggie-burger may be similar, the tears produced in each case are distinctly different.

There are three types of tears produced by our eyes which are classified as basal, reflex and emotional (psychogenic) tears .

Basal tears, which are the primary tear, help keep the eye surface nice and moist. The chemical components of this tear class allow it to form an adherent, thin film over the eye to provide general protection and moisture.

Sometimes we may get things like dust or a pellet from a Red Ryder BB gun in the eye. We all make mistakes. Such irritants will induce the response of reflex tears. Reflex tears hold similarity to basal tears, but are distinct in having chemical components that more readily allow elimination of particles and irritants (like dust or onion vapors) and microorganisms.

The final class of tears, and the ones that produce many scientific questions, are emotional tears. Some studies and scientists indicate this class of tear, within humans, are different within males and females and also may have a distinct evolutionary origin and physiological purpose.

Certain chemicals may build-up when the body is under great stress. Studies have shown that proteins released in emotional tears are the same hormones associated with high stress. For instance, prolactin (protein associated with breastmilk production) and adrenocorticotropic hormone (ACTH) are both associated with emotional tears and also stress within the body.

Women tend to have higher prolactin levels, nearly double, than that of men and this may be why women cry a bit more easily when under stress. ACTH, often associated with the "sweating bullets" you see on a guy who has forgotten his anniversary or is pushing a deadline, is stress associated and released in emotional tears. Research shows that suppressing emotional tears may contribute to conditions such as hypertension and heart disease.

The most mysterious and enigmatic part of crying comes from the most recognized use of tears in today's society; communication. At a funeral or during a sad event, cultural norm shows expressing sadness in tears is comforting and common. This seems to be an emotional response that covers many cultures. The same way adults use crying to show an emotional bond, babies and young children use crying (with associated tears) as a symbol of communication to show pain, hunger or perhaps hurt. The evolutionary and physiological aspect of the communication of crying, in humans and perhaps some animals, still has many points of consideration to explore.

Fun Fact: Why Do Onions Make You Cry?

We all know that onions make us tear up. The next time you are around someone who is cutting up an onion, impress them with your scientific knowledge.

Onions contain amino acid sulfoxides, which are a type of organic molecule. When you cut into the onion skin, allinases, a class of enzymes, mix with the sulfoxides to make sulfenic acid. Once exposed to oxygen in the air, the sulfenic acid arranges into the strong chemicals syn-propanethial-S-oxide and thiosulfinates, which cause tears and cause the strong smell of cut onion, respectively. It's not the scent of the onion that makes you cry, but rather the syn-propanethial-S-oxide irritating the eye that makes you release reflex tears and cry. Since the chemical makes you cry it's also called a lachrymator.

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