Why does water spill out of our faces?

And where does the water come from?  I mean, obviously I know that tears come out of tear ducts, but where is the water before that?  Do we have little reservoirs of salty water that wait for the next moment where we feel sad enough to involuntarily open the dam for a while?  And when we do feel that way, why is it our bodies' natural response (but for some people more than others) to just... leak?

It makes sense that we should have a biological mechanism to wash particles out of our eyes when dust blows or small insects demonstrate their lack of intelligent flight patterns, and it also makes sense that babies need a nonverbal method of communicating their needs while developing the language processing parts of their brains.  The part that gets me, though, is why we continue to have the crying reflex as adults in those moments when we are physically hurt, or deeply sad, or angry, or even overjoyed.  By adulthood, we have full capability to express our thoughts, feelings, and needs verbally (or at least, theoretically we do -- some people seem to be severely lacking in effective communication skills, but I think that's a different issue... As my sister and I frequently quip each other in the most high-pitched, fakely sweet, condescending voice possible:  "Use your words...").

Anyway, the point is, why does my freaking face have to leak whenever I feel even remotely sad or frustrated or too happy?

During my first attempts to solve these mysteries, I thought, Let's Google "anatomy of a tear duct" and see what happens.  Maybe we'll find the hidden saltwater reservoirs.  

Well, the first image I clicked was this one:  

Thank you, Will, for that amusing but entirely uninformative diagram.  

Let's try this one instead:  

Now, I can study this image while murmuring some ahhhs and mmhmms of outstanding intellect and instantaneous understanding, but let's be honest.  This tells me nothing (other than that the picture suggests we do, indeed, have tear reservoirs).

Time for some further investigation...

Apparently, the lacrimal ducts and glands (a.k.a. the tear ducts and glands) "produce and distribute the watery component of the tear film.  Tears consist of a complex and usually clear fluid that is diffused between the eye and the eyelid.  Further components of the tear film include an inner mucous layer produced by specialized conjunctival cells and an outer lipid layer produced by meibomian glands along the eyelid margin" (Encyclopaedia Brittanica).

Some thoughts:  Tear film??  Usually clear??  Mucous??  Gross.

Well I'm glad that my tears are there to keep my eyeballs from drying out and stuff, but I still don't know why the water has to pour out in excesses at such vulnerable and inconvenient times.

More Googling...

Aha!  Google always knows the answers.  There are three types of tears:  basal (which are always there keeping your eyeballs appropriately moist), reflex (which are there to clean out the bad stuff), and emotional.  The elusive emotional tears are the ones I'm interested in.  HowStuffWorks tells me:

"It all starts in the cerebrum where sadness is registered. The endocrine system is then triggered to release hormones to the ocular area, which then causes tears to form. Emotional tears are common among people who see Bambi's mother die or who suffer personal losses."

But whyyy?

"Chemicals build up in the body during times of elevated stress.  [Some] researchers believe that emotional crying is the body's way of ridding itself of these toxins and waste products.  In fact, one study collected both reflex tears and emotional tears (after peeling an onion and watching a sad movie, respectively). When scientists analyzed the content of the tears, they found each type was very different. Reflex tears are generally found to be about 98 percent water, whereas several chemicals are commonly present in emotional tears [Source: The Daily Journal]. First is a protein called prolactin, which is also known to control breast milk production. Adrenocorticotropic hormones are also common and indicate high stress levels. The other chemical found in emotional tears is leucine-enkephalin, an endorphin that reduces pain and works to improve mood. Of course, many scientists point out that research in this area is very limited and should be further studied before any conclusion can be made."

Keep reading...

"After babyhood ends, researchers believe that girls and boys do equal amounts of crying until they reach the hormone-fraught adolescent years. As levels of testosterone skyrocket in boys, their amount of crying plummets. The opposite is true for girls, whose estrogen levels begin to rise substantially during the early teenage years. This is especially interesting, considering the relationship between the protein prolactin and breast milk production, which only happens in women. Perhaps this is why women cry roughly four times as much as men, according to biochemist and researcher William Frey and co-author Muriel Langseth, who wrote Crying: The Mystery of Tears.'  Frey estimates that women have about 60 percent more prolactin in their bodies at any given time than men [source: Women's Health]. He also believes that these elevated levels cause women to cry more because the protein revs up the endocrine system, which makes people more likely to cry."

Thank you, HowStuffWorks.  I now understand (however superficially) that there are biochemical processes involved and that crying actually serves a purpose.  For more details, click on the previous link.  Or Google it yourself.  I'm gonna go read the last Harry Potter book and cry my eyes out now.