Bodily functions

Our bodies are complex biological machines performing millions of tasks all the time, most of which we aren’t aware of. But occasionally some function of this machine draws itself to our attention, usually at an inopportune time.

Just why certain bodily functions are embarrassing and/or annoying to ourselves and those around us, when, after all, they are functions we all share, is a question for sociologists, not me. But I can, perhaps, explain some of these functions scientifically–at least, those that are marginally acceptable in polite conversation. (Perhaps I’ll save those that aren’t for a later column!)

Here’s one every kid has been warned of: cracking knuckles “You’ll get arthritis if you keep that up!”, your mother may have said, but Mom was wrong: studies show that knuckle cracking does not lead to joint problems.

Nobody knows for sure what causes the popping noise, but the best guess is that gases dissolved in the fluids that lubricate our joints undissolve, forming bubbles, when the joints aren’t flexed for a while. Applying force in the opposite direction to the joint’s normal movement pops these tiny bubbles with a sharp cracking sound.

Those of us who occasionally crack our knuckles (you know who you are) find it a pleasurable (and addictive) activity, although how much of that pleasure derives from the act itself and how much from the annoyance of others is an open question.

Nobody finds pleasure in another common and annoying bodily function, bad breath. In general, like most odors associated with the body, bad breath is caused by the excretion of bad-smelling chemicals by multiplying bacteria. The bacteria grow in food particles trapped in the mouth. Certain foods such as garlic, onions and fish, all of which contain sulfur, can add their own inherent odors to this problem.

Saliva, the mouth’s natural cleansing agent, helps wash away odor-causing bacteria. Saliva production is stimulated by chewing and swallowing, so during the night, saliva production slows. That’s why “morning breath is the worst breath of the day.”

Regular brushing and flossing is the best treatment for bad breath, because it gets rid of the food deposits on which the odiferous bacteria feed.

Being hungry (did I mention I’m on a diet?) can also cause bad breath, because the digestive juices in an empty stomach start to break down, producing an odor that rises to the mouth. In addition, a hungry body starts to burn its own fat, which can also release bad-smelling chemicals.

Being hungry (did I mention I’m–oh, I guess I did) is related to another sometimes embarrassing bodily function, the growling stomach. Our digestive process produces gases as a by-product. When the digestive system is mostly empty of food, these gases are free to travel around inside the intestines, vibrating our internal plumbing and causing growling noises. (Where these gases eventually end up is a bodily function which crosses over that line from almost-acceptable topic of conversation to conversation-stopper.)

Moving up and out of the body, to the very top, we discover an external embarrassment: dandruff. All of us shed millions of cells of dried skin every day. Our hair, being thick and oily, traps this dried skin, accumulating it as small white flakes which are eventually shed, usually onto the shoulders of that tuxedo you rented to impress your girlfriend.

Dandruff is most noticeable between ages 10 and 20, and generally improves after age 30, which is a comfort, I guess, unless of course you have less dandruff after age 30 because you have less hair to trap skin cells. In the meantime, there are shampoos that help decrease skin cell turnover on the scalp and thus reduce dandruff. Their magic ingredient is not prominently featured in their advertising, for obvious reasons: it’s tar.

After our brief sojourn to the sunlit, breeze-swept peak of the head, let’s plunge back down into the body’s tropical jungles: the armpits. Here, in the warm, moist darkness, we find teeming life: more of those odor-producing bacteria we last encountered in the cavern of the mouth.

Our perspiration not only cools us through evaporation, it also carries out of the body a variety of organic compounds which are prime fodder for bacteria. On most of the body, perspiration quickly dries, giving bacteria little chance to grow. But under our arms and in other enclosed areas, such as our shoe-encased feet and our–well, never mind–these bacteria can multiply undisturbed.

Interestingly, researchers recently identified the prime ingredient in essence d’armpit: 3-methyl-2-hexenoic acid. As the scientist who led the research team puts it, having of vial of 3-methyl-2-hexenoic acid in your possession “is like having an armpit in a jar.”

Should the details of internal gases and external odors have failed to interest you, you may by this time be yawning, another bodily function that can occur at inopportune times, such as when your boss is giving a speech and you’re sharing the head table.

Yawning is a reflex that occurs when the nerves in the brain stem (the most primitive part of the brain) detects a build-up of carbon dioxide in the blood. Your mouth and throat muscles spasm, forcing your mouth as wide open as possible to allow the carbon dioxide to escape. At the same time, your chest cavity expands, so you can suck in lots of oxygen-rich air. All of this, for some reason, is contagious: try yawning in a crowded room and see how many other people follow suit.

Although you can consciously make yourself yawn, you can’t consciously stop a yawn from happening. (Tell your boss that. Maybe it’ll help.)

Should you be yawning incessantly, you might want to take a nap. When you awake, you could find little gritty bits of something at the corner of your eye: sleep dust.

Sleep dust isn’t dust at all–it’s really dried tears. Tears are made of three layers, a bottom layer of mucus, a layer of water; and a layer of fats, called the lipid layer. While we’re asleep, these three layers get disrupted by the movement of our eyes inside our closed eyelids. The lipid layer interacts with the mucal layer to make a gooey substance that collects at the corner of the eyes (where tears normally exit into the nasal cavity) and dries out, forming little crusty granules.

There are many other bodily functions we could discuss, but space will not allow us to immerse ourselves in the fascinating world of mucus, or the dizzying depths of nausea.

But stay tuned: I’m planning a sequel.

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