Friday, July 17, 2015

Playing Defense

Last week, my body came under attack. In an ironic twist following last week’s post on contagious pathogens, I picked up a nasty bug that for the past seven days has wreaked havoc on my immune system. Fortunately, whatever I caught was confined to my northern regions – primarily my throat and chest – rendering me febrile, voiceless, and with a bone-rattling cough that could give any tubercular a run for his money.

I’m happy to report that I am now on the mend, but it got me thinking about the immune system and the vital role it plays in keeping us safe. Naturally, I thought I would elucidate its magical machinations, but I found myself resorting to boring military metaphors traditionally employed for such discussions. The trusty lymphocytes that serve as armed forces, always on high alert and ready to mobilize should a foreign invader appear on the horizon. Pathogens, those dangerous usurpers who are just waiting for the opportunity to bust through our protected borders. Blah, blah, blah.

So instead of the usual immunity song and dance, I thought we’d explore the more perceptible means of defense, for our bodies have evolved numerous nifty ways to rid themselves of unwanted guests.

First and foremost is that largest of organs, the skin, which accounts for around sixteen percent of our body weight. Skin serves as a protective barrier against our pathogen-infested world and it does this not only through its layered arrangement, but also by producing specialized peptides that annihilate microbes and sound the alert when danger approaches.

But there are two problems when it comes to skin’s defenses. First, skin tears. And once it is torn – whether through an injury, an insect bite, or on purpose, through surgery, it allows entry to all sorts of dangerous organisms, from bacteria, to viruses, to parasites.

The second problem concerns topography: although our skin is one large organ, it varies from surface to surface, and some of our most vulnerable surfaces are those that house our mucous membranes. For example, the respiratory tract. The moist, gooey surfaces of our respiratory system provide the perfect portals for pathogens. Each time we put a hand to our mouth, pick our nose, or simply take a breath, we can usher in a suite of infectious organisms that would love to plant their flag.

Fortunately, our respiratory tracts have devised a few clever ways of ridding themselves of pesky pests, which explains why we cough, sneeze, dribble, and blow. Our lungs also sport a thin layer of microbe-fighting proteins, which defend against any bugs that manage to weather the snotty storm.

But pathogens are crafty. Some, like influenza, actually attach themselves to our bronchial membranes to prevent their quick expulsion. Others, such as measles and whooping cough, render our cilia inoperable. Those small, hair-like projections are designed to usher pathogens up, up, and away from our lungs, and when they are knocked off-line, bugs can simply run rampant.

The respiratory tract is but one of many portals for pathogens. Our stomachs are prime targets for many food- and waterborne bugs, which cause a wide range of misery, illness, and death. Luckily, our stomachs make for fairly acidic accommodations, with an average pH of about 2 (which you science nerds will recognize as pretty darn acidic). And just like our respiratory tracts, our gastrointestinal plumbing has devised a couple of rapid evacuation methods, namely vomiting and diarrhea.

And speaking of acidic body parts, let’s not forget the vagina. This acidy little tube sports a pH of around 4, which is ideal for warding off bacterial and fungal invaders - not to mention sperm, which explains their desperate swimming. Not so, our urethras, which is why urinary tract infections are so common. Especially in women, for not only do our urethras lack defenses, but they are positioned dangerously close to the anus, which as we all know is a virtual playground for pathogens.

And speaking of that other southerly portal… The anus, like the urethra, is also ill-equipped to ward off infection. And what makes it even more dangerous is that, unlike the vagina, the anus lacks any natural lubrication. So if you’re going to use it for recreational purposes, do yourself a favor and lube up. It will prevent tissue tears, which are great access points for infection. And don’t forget the condom!

So the next time you find yourself sneezing, coughing, vomiting, or worse, take a moment to appreciate the fundamental necessity of such functions and know that as miserable as these symptoms are, they serve a vital role in the fight against pathogens.

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