That dangly, speed-bag-looking thing at the rear of your mouth is called your palatine uvula, or just uvula for short. What's it for? That's a good question. People have been asking this for hundreds of years (seriously), and their answers are... mysterious.
Consider the abstract to "The riddle of the uvula," a study published by otolaryngologist Yehuda Finkelstein and colleagues in a 1992 issue of Otolaryngology – Head and Neck Surgery:
Investigators have been interested in the structure and function of the uvula for centuries. Some of them emphasized its influence on the tone of voice, others its immunological role. Since the times of Hippocrates, people have been afraid of the uvula oedema, as it could lead to apnea and death. It was also suspected that upper airway diseases originated from the uvula.
To this day, the uvula remains poorly understood. For instance, when I read the abstract above, my curiosity was piqued by the claim that it might have some influence on the tone of one's voice. Intrigued, I put the question to my friend Katie Plattner, a speech-language pathologist and all around smart lady: Why do we have uvulas?
"I think one theory is to increase surface area where a gag reflex can be triggered so nothing too big gets down there without you knowing," she replied. She then added: "I also might have made that up, but [it] seems right."
When I asked Plattner if I could quote her, she said "If you include that I don't really know, sure!" Why would I quote her if she's not really sure? Because it turns out the theory she floats actually stands up. More importantly, though, her qualification of that theory captures a lot of the uncertainty that surrounds the uvula and its function.
Plattner is right, for example, that the uvula's raison d'être may have something to do with its facilitation of the gag reflex. I would tell you to test this hypothesis for yourself, as I did (when I carefully prodded at my uvula with the head of a toothbrush, I did, in fact, gag), but why would you put yourself through that when you could just as easily reference "The etiology and management of gagging: A review of the literature"? The study clearly identifies the uvula as one of five* major "trigger zones" capable of eliciting the gag reflex through tactile stimulation. (Speaking of gagging, some people get their uvulas pierced. Maybe some uvulas are more sensitive than others?)
But the idea that the uvula exists to make you gag is just one of many theories pertaining to its function. In a literature review published in a 2004 issue of Clinical Otolaryngology, Andrew Coatesworth and his colleagues at the Department of Otolaryngology at England's York District Hospital run through a list of myths and theories that have been attributed to uvulas throughout the ages. One of the most enduring theories, dating all the way back to the 2nd Century, has to do with the uvula's role in speech:
Galan (122–199 AD) believed that the uvula was important in speech and contributed to the beauty of the voice. In modern times, many theories have also been put forward with regards to the role of the uvula in speech: the uvula prevents excessive nasality of the voice by controlling resonance of the air column over the larynx; the uvula is important in the production of uvular sounds present in French, Arabic and some West African languages and palatal trill found in some parts of Yorkshire in the United Kingdom.
By observing patients who have had their uvulas removed through a procedure known as a uvulectomy, researchers have been able to test some of these theories. In one study, patients who had undergone radical uvulectomy lost the ability to produce uvular sounds, whereas partial uvulectomy resulted only in changes to the voice's quality. Another investigation found that uvulectomy had deleterious effects on neither speech nor swallowing. Another, still, found that uvulectomy could actually facilitate speech. As for its ability to prevent nasally speech, it seems the muscularis uvula (the muscle that elevates and retracts the uvula), and not the uvula itself, is required to prevent hypernasality during speech.
There are many other theories, most of which have not been thoroughly tested. One states that the uvula exists to block off the nasopharynx (the upper portion of the cavity connecting the nose and mouth with the esophagus) during speech and swallowing. Another maintains that the uvula acts like a goalie for your airway, preventing food and stray liquids from zipping down the wrong pipe. Another, still, states that the uvula acts as a drain for the mucous secreted from the nasal cavities, and directs its flow towards the base of the tongue. Here are a few more suppositions about the uvula (this list via the folks at Mental Floss):
- That it once helped guide the flow of food and water, and, in humans, was a mere remnant from previous mammals who had to lean down to eat and drink.
- That it contributed to "chronic cough." A problem that 19th-century doctors treated with a "simple" "clipping" procedure.
- That it contributes to cardiovascular problems like sudden infant death syndrome (SIDS) and sleep apnea.
What's interesting about these hypotheses is that they all seem plausible, to varying degrees. For example, in 2004, a doctor at Royal Alexandra Children's Hospital in Brighton, UK reported "a case of a long, floppy uvula causing chronic cough through mechanical irritation" of the upper airway. And the idea that the uvula is somehow implicated in cases of obstructive sleep apnea appears to be supported by patients who report improvements after undergoing "uvulopalatopharyngoplasty" (or "UPPP"), a procedure in which excess tissue in the throat – including the uvula – is removed to widen and clear the patient's airway.
But reports of "long, floppy uvulas" causing chronic cough are pretty rare, and some studies have shown that when people with sleep apnea have their uvulas surgically removed, it's effectively a coin flip as to whether their symptoms worsen or improve. And besides, studies like these tell us more about how our uvulas revolt and turn against us than what they do to help and support us. The question, after all, isn't what happens when good uvulas go bad? It's what good are uvulas in the first place?
Apart from the gag reflex thing, the most compelling theories I've come across all revolve around the uvula's role in human speech. Remember "The riddle of the uvula," the 1992 paper by Finkelstein et al.? Part of the investigation included a study of a variety of animals, including sheep, chimps, and baboons. Of the animals studied, the researchers found only two baboons to have uvulas, and they were underdeveloped uvulas, at that. If only humans have uvulas, and speech is unique to humans, then perhaps the uvula evolved to aid in human speech.
In their 2004 paper , Coatesworth and his colleagues present a new theory that lends credence to the uvula's significance as an organ of speech (emphasis added):
Recent histological studies have shown the uvula to have an abundance of seromucous glands with the ability to produce large volumes of thin saliva. A common late complication involving removal of the uvula is pharyngeal dryness. While examining patients with flexible nasoendoscopy [an instrument that allows for visual observation of the nose/throat system; photos acquired by the instrument, which show a uvula swinging back and forth during swallowing, appear above] in the ENT outpatients, we have observed that on phonation the uvula swings back and forth in the oropharynx. Our theory is that the uvula bastes the pharynx and keeps it moist and well-lubricated.
As Coatesworth's team notes, "the jury is still out on exactly why it is we have a uvula," though its uniqueness among mammals, and its roles in speech, swallowing and throat-lubrication suggest it's not a vestigial trait, as some have proposed. I think I can live with that answer. After all, "gag-inducing, speech-modulating throat-baster" is one hell of a job description, if you ask me.