Friday, August 30, 2013

Eruption in Your Mouth...

Date: Thanksgiving Day, early 1970s.
Location: Subic Bay, Philippines.

Subject: A budding tomboy, bored with waiting for turkey, heads out to her favorite tree.

Event: While doing her best impression of a ring-tailed lemur, she loses her grip and plummets to the ground.

Status: Two front teeth, missing in action.

This scenario played out when I was just a child. The teeth were never found. Luckily, my permanent incisors came in strong and healthy, but this would be the beginning of a series of dental dramas.

I was born with a very small jaw. As my permanent teeth erupted, it was clear I lacked room for a full arcade, so by the time I entered my teens, it was time to take action.

They started with my premolars, yanking four of them to provide a bit of breathing room. Then came the braces; I’m talking the clunky metal kind that were oh-so-attractive. Once the unsightly apparatus was in place, the assistant set to work carefully chipping away the excess concrete from around the bands. As the tiny flecks hit the back of my throat, they triggered my gag reflex and the next thing I knew I was hurling a partially digested egg sandwich into that tiny sink. (FYI: Those little sinks only accommodate spit.)

During my two-and-a-half-year tenure in braces, it was decided things were still too crowded, so out came my wisdom teeth. I’ve spent decades trying to convince my dentist I deserve a discount, since I lack a quarter of my inventory.

The final insult occurred on the racquetball court. I was kicking ass against two fellow firefighters when I took a racquet to the pie-hole, shattering my two front teeth. Fortunately, I had a gifted dentist who was able to reconstruct them and today, no one’s the wiser.

Teeth are important. If you’ve never stopped to appreciate them, take a moment. Imagine gnawing on a juicy steak, or biting into a delicious apple. As I said, teeth are important.

I bet you’re wondering how teeth are formed. It just so happens, I have the answer.

Tooth development, known as odontogenesis, begins in the womb and is controlled by over three hundred genes. By the fourth week of embryological development, the upper and lower dental arches are formed. The arches are covered by specialized cells that will eventually become the tooth buds; ten on top, ten on the bottom. The buds develop a cap of enamel, forming the crown, and dentin comprises the interior.

The deciduous, or primary, teeth are hidden within the jaws when we are born. The first to erupt are the two bottom incisors, usually when we’re around six months old. The first molars erupt around our first birthday and the rest of the dentition quickly follows. Thus, you sport a beautiful arcade of twenty tiny teeth by the time you are three.

Then the permanents start shoving their way out.

The twenty baby teeth will eventually be replaced by thirty-two permanent teeth. Lower first molars usually take the lead, erupting around the age of six.  The last to appear are the third molars, or wisdom teeth, usually in our late teens.

Permanent teeth come in four varieties: incisors, canines, premolars, and molars (front to back, respectively), and their shape is dictated by function. Incisors allow us to cut. Think back to that delicious apple… The canines are for tearing (or puncturing, if you’re a vampire). The premolars serve a dual purpose: tearing and crushing. And the molars, with their broad, bumpy surfaces, are for grinding. (Run your tongue along the chewing surfaces of your teeth and you’ll note the dramatic changes in shape)

Teeth hold information about our biological history. Dental traits are passed along as people move and mate. For example, the fascinating shovel-shaped incisors of Native Americans were one of the first clues to their Asian origins.

Our teeth are part of our evolutionary history. Over time they, along with our faces, have gotten smaller. Smaller jaws mean more crowding, thus the need for so many of us to have our wisdom teeth yanked.

But aside from the crowding, our teeth suit us to a tee. They allow us to chew, which aids digestion; they assist in speech by allowing us to form sounds; and they are key to good nutrition, for it's hard to be healthy if your teeth fall out of your head.

So now that you know how teeth erupt, stay tuned. Next week we’ll discuss some of the bizarre ways we alter and adorn our teeth as we explore the exotic custom of dental mutilation.

Tooth eruption video!

Saturday, August 24, 2013

Timing is everything...

The other morning, I burnt my eggs. I put six jumbos on to boil, anticipating the delight of an egg salad sandwich, but forgot to set the timer before sitting down to write. Forty minutes later, my concentration was broken by a loud popping sound emanating from the kitchen. I rushed to the stove as, one by one, my eggs exploded.
As I scraped the pot, I got to thinking about timing.

Timing was a major theme in my previous occupation. The job of a firefighter/paramedic 
revolves around timing: how quickly you arrive on scene, how fast you get water on the fire, and how rapidly a patient is transported to the hospital. At OFD, even getting to our trucks was timed. We had to be responding to the call within one minute, or else! If you were in the shower or “taking care of business,” too bad. In emergency services, timing is critical.

Now that I’m an archaeologist, timing takes on different dimensions. I no longer deal in minutes; my research spans centuries and millennia. Thus, it was a shock to my system transitioning from the heart-pounding, adrenaline-pumping pace of emergency medicine to the tedious, methodical approach of archaeology.

As a firefighter, I experienced the joy of destruction. It’s critical to open up confined spaces to search out hidden flames, so at every fire, we would blissfully tear out walls and pull ceilings. God, it was fun.

Archaeology, on the other hand, requires painstaking excavation, the meticulous exposure of a site’s history. My archaeological field school was an excruciating trial in patience. I imagined driving my fist through those perfect walls, taking a sledge to those stubborn soils. It’s probably best I stick to the lab.

But it turns out timing is critical to my work as a bioarchaeologist, for the analysis of human remains is based on timing. Here’s how:

For every skeleton that comes out of the ground, a basic assessment is conducted. This is the information that provides the fundamentals of bioarchaeological research. It all begins with sex (as everything should).

The sex of the individual is determined based on the size and shape of bones, as well as certain landmarks on the skeleton. This is where timing comes in, for only after puberty do our skeletons develop the characteristic traits that distinguish male from female. The skull and pelvis morph with sexual maturity, making it fairly simple to identify the sex. Unfortunately, we lack a definitive means of sexing children, unless we’re lucky enough to obtain DNA.

Determining the age at death is also based on timing. For children, the eruption of teeth provides a wonderful tool, since we know, on average, when each tooth emerges in the mouth. For adults, we use certain surfaces on the skeleton, primarily the pelvis, because these surfaces change as we age.

Height is determined by measuring the long bones of the body, primarily the femur. The length of the bone is put into a regression formula, which reveals the overall height of the body. But once again, timing plays a role. Growth in children depends on the quality of their diet, their exposure to disease, and, of course, genetics. But even if a child’s growth is challenged, science has shown that children can experience “catch-up growth” in their teens, should conditions improve.

So why do we care about the sex, age, and height of individuals long dead? Because this information provides the tools with which we reconstruct past lives.

For example, let’s say we excavate a cemetery of one hundred well-preserved skeletons (every bioarchaeologist’s dream). If we know the sex of the individuals, we can deduce aspects of their social structure. If the majority of the skeletons are male, perhaps they were engaged in intensive warfare. An abundance of females may indicate differential access to high quality foods.

The age of the individual at death is also revealing. If the majority in our cemetery are children, it speaks to the overall fitness of the population, since high child mortality does not bode well for healthy peeps. 

Height also provides information about overall health, for you’re not going to grow big and strong if you’re undernourished and plagued by pathogens.

So even though I no longer treat patients or fight fires, timing is still fundamental to my existence. As the skeleton grows and matures, it changes, and it’s these changes that provide the building blocks of bioarchaeological research by allowing us to tease information from the fragile remains of those who lived thousands of years in the past. Amazing!

What I consider the bible of bioarchaeology: an oldy but a goody.

Sunday, August 18, 2013

Skin Deep

I want you to think about your skin. Not simply a patch of it or the parts you don’t like. I want you to picture it in its entirety.

Start with your head and try to envision the one hundred thousand hair follicles that adorn your gourd (hairless individuals please proceed to the next paragraph).

Think about the skin on your face, how time etches its history on our features. If you’re like me, you get a sinking feeling whenever you happen by one of those god-awful magnification mirrors (I really think those things should be outlawed).
Now picture the skin of your torso. If you’re a fish-belly from up north, the skin on your abdomen is probably pretty pasty. For those of us living in the Sunbelt, we tend to accumulate a rash of freckles, especially on our shoulders, as we bake our way through life.

Proceed to your limbs. The skin on our arms tends to be of a tougher nature, since it’s frequently exposed to the elements. We’re all familiar with the “farmer’s tan” – bronzed forearms and a matching neck (thus, that lovely term "redneck"). For centuries, women have caked their faces with powder to reaffirm they in no way participate in manual labor.
And finally, picture the skin on the palms of your hands and the soles of your feet. Those thick, waxy surfaces can’t support hair follicles; thus they are the only places on our bodies lacking hair.

The point of this exercise is to show that although our skin is one continuous organ - yes, it’s an organ and the largest one, to boot! -  it’s unique. Unlike the other organs in your body, it has a wide range of textures, sports varying degrees of hairiness, and comes in a beautiful assortment of colors.
We’ve already discussed the embryological development of the skin in April's “Disfigured." As a quick review, skin arises from the ectoderm, that outermost germ layer from which many of the external features develop, such as hair and nails. The skin is composed of three layers: the epidermis (outermost layer), the dermis (middle layer), and the subcutaneous (you guessed it – the inner layer). The subcutaneous, also known as the hypodermis, contains the nerves, the blood vessels, and the roots of our hair follicles.

This layering becomes significant in the cases of burns. A burn is categorized according to its depth. First degree burns are superficial and involve only the epidermis; sunburn is a good example. Second degree burns are those that affect the dermal layer and typically produce rubbery, fluid-filled blisters. Third degree burns, also known as “full thickness burns,” penetrate the entire dermis. And finally, the ghastly (but rare) fourth degree burns involve muscle and bone.
Which kind of burn hurts the most, you ask? Surprisingly, it’s the second degree variety, since full thickness burns typically destroy the nerves. No nerves means no pain. It’s at the periphery of the third degree burns, where third fades to second, that the pain resides. And we’re talking major pain.

When we were kids, my sister suffered severe scalds to her lower legs when she climbed up onto the kitchen counter and spilled a pot of boiling water. She developed a whopper of a blister on her foot and I remember the fascinating way it would dimple when I pushed on it with my dainty finger.
If only she had been a rhino. A rhino’s skin is up to five centimeters thick. I bet it’s hard to scald a rhino.

It could have been worse; she could have been a frog. Like many amphibians, our little froggy friends possess the unique ability to absorb water through their skin, which they utilize in place of drinking. They can also breathe through their skin. But, sadly, it’s these amazing gifts that make them so vulnerable to pollution.
And here’s a curious fact: polar bears – the most Caucasian of bears – actually sport black skin under all that white fur! (Word of caution - do NOT Google "naked polar bears"!)

Our skin is an amazing organ. It not only holds everything in place (for the most part), it also protects us from pathogens, regulates our body temperature, and allows us to experience the world around us.
Imagine a world with no sensation, a world devoid of feeling. Think how important human contact is: the warmth of a hug, the thrill of a touch. Yes, we could do with less pain and suffering, but the pain reminds us we are alive. Pain and pleasure ground us to our world and much of that pain and pleasure we experience through that wondrous medium, the skin.

Sunday, August 11, 2013

Guts and Glory

I have a confession to make: I’m obsessed with roadkill. I can’t even drive to work in the morning without gazing, mesmerized, at the previous night’s slaughter. Living on the Florida coast provides ample opportunity, for there resides a plethora of potential victims. Raccoons, possums, and armadillos make for regular roadside fodder and their mangled, bloated bodies litter our otherwise scenic highways.

I’ve made a game of it. My favorite pastime, especially on long trips, is to try to identify the critter. Heads and tails are the most useful diagnostics, since these creatures are of similar size and their appearance tends to blur once decomposition sets in.

This hobby started when I was just a child and is grounded in my fascination with internal organs. I learned early on that roadkill afforded a rare glimpse at innards and I became so enamored of splattered guts that I once chased a large toad into the road and then crouched behind a bush until the inevitable car came along and flattened him. I quickly set to work inspecting the colorful smear; that is until my sister ran inside and tattled. My parents were not amused…

As one fascinated with guts, I chose the perfect profession. As a paramedic, I responded to a glut of horrific accidents that left behind mangled victims. Car crashes, stabbings, and shootings are just a few of the ways to lay open a body, revealing the beautiful, glistening entrails. In cases where the abdomen is intact, medics are taught to evaluate the belly by dividing it into four quadrants. For example, appendicitis pain typically flares in the right lower quadrant, although it's also common to have pain around the belly button, or periumbilical, if you want to sound sophisticated. By knowing where each structure resides, you can narrow down the suspect organ, based on where the patient points. So let's take a quick tour.

The human body is made up of various systems, such as the respiratory, digestive, and reproductive. These systems are composed of organs, which work together to perform certain functions. All humans have the same organ systems, with the exception of our sexual organs (unless of course you’re a hermaphrodite and blessed with both male and female parts).

Organs are either hollow - those you can insert a finger into, or solid, which you can slice like a nice block of tofu. They both have unique attributes when it comes to injuries. Solid organs, like the liver, can bleed profusely when torn or bruised, since they house extensive networks of vessels. Hollow organs, such as the intestines, tend to leak their contents when damaged, which can lead to massive infection. It's pretty much a lose-lose situation when it comes to damaging your guts.

The largest of our internal organs is the liver. It weighs on average about two and a half pounds, is nestled just below the diaphragm on the right side of the body, and is tasked with getting rid of toxins. The amazing thing about the liver is its ability to regenerate; if you remove a chunk, it can grow back!

But the liver is just one of many organs housed within our abdominal cavity. Its neighbors include the stomach, pancreas, and spleen, along with the intestines (large and small varieties) and those cute little kidneys in the back. In fact, those cute little kidneys are composed of about 140 miles of tubes and more than a million filters, and are able to cleanse the body’s entire blood supply about twelve times per hour!
Quite impressive.

You may be asking yourself, “What the hell is that spleen all about?”

Yes, the spleen is a lesser-known organ. Kind of like that poor astronaut who jumped onto the moon right after Neil Armstrong. But the spleen is an important part of our immune system, storing white blood cells and getting rid of worn out red ones.

What you may not realize is the important role the skeleton plays in the protection and suspension of these organs. First there is our pelvis, which cradles our organs like a basin (and you thought your pelvis was only involved in walking and sitting). Our ribcage houses and protects our heart and lungs, but also those organs just beneath them (liver, spleen and pancreas). And many of our organs are suspended via the peritoneum, which keeps them from sloshing around willy-nilly in our bellies. All of this is accomplished by our awesome bony frames and is just another example of the beautiful and intricate organization of the body.

So you may abhor my lust for squished critters, and I’m not requiring  you take it up as a pastime, but the next time you’re confronted by a mangled roadside victim, take a peek - you just might enjoy it.

And now for your viewing pleasure, here's a great video, giving you a tour of the abdominal cavity!


Sunday, August 4, 2013

Scars and Souvenirs

This morning, out of curiosity, I counted my scars. I did a head-to-toe survey, the way I was taught in paramedic school, and came up with a grand total of fifteen scars I’ve accumulated while strolling (and stumbling) down this road of life.

I find scars fascinating. They tell stories; they speak of the past. They are small (and sometimes gruesome) reminders of events in our lives. Some are accidental (where I tore my finger open on a hydrant during the fire academy); some intentional (the faint line in my belly button from a tubal ligation); and some are simply consequential – like the chicken pox scar on my forehead. They mark moments in life that are indelibly etched onto our bodies.

So what are scars and how are they different from normal tissue? Let’s start with a scenario:

Say you’re strolling down the beach and you fail to notice the broken bottle some drunken cretin has tossed into the surf. The bottle has now washed ashore, landing right in your flight path. The next thing you know, your foot is laid open and you’re hobbled. Two things happen. First, if you’re like me, you curse like a sailor and proclaim your hatred for the common litterbug. Second, your body responds to the insult by forming a clot around the wound and sending fibroblasts, which help rebuild tissue, to the site. As the fibroblasts break down the clot, they replace it with proteins – primarily collagen – that will eventually form the scar tissue.

Scars are made up of the same tissue as normal skin, it’s just the arrangement of the collagen fibers that sets them apart. In normal skin, the collagen is arranged randomly. In scar tissue, however, the fibers are generally aligned in a single direction. This is why scars look and feel different from the surrounding tissue. And here’s an interesting tidbit: scars lack hair, sweat glands, and a normal blood supply (think of them as middle-aged men, except for that part about the sweating).

External scars are fairly benign. Although they lack the flexibility of normal tissue, they typically just dot our landscape and remind us of bygone events. It’s when scar tissue forms on the inside of the body that the real trouble begins, and some of our most common diseases are linked to scarring.

Heart attacks (technically called myocardial infarctions), occur when a blockage in a heart vessel leads to death of the surrounding tissue. The damaged tissue can scar, which can then lead to arrhythmias (irregular beats or rates). Arrhythmias, such as atrial fibrillation, can subsequently lead to stroke. Scar tissue within the heart has also been linked to sudden cardiac death in people with certain preexisting conditions, such as cardiomyopathy.

Diabetes is also linked to scarring, as those who neglect to regulate the amount of sugar in their blood can suffer on multiple fronts. High sugar levels cause the smallest of blood vessels to burst, which can lead to scarring, and scarring around organs, such as the kidneys, can lead to failure, which is never a good thing.

One of the scariest diseases involving scarring is called scleroderma. Scleroderma results from an overproduction of collagen, those same fibers that create scars. These fibers can accumulate on or within the body, wreaking havoc along the way. Affected fingertips can develop pitting and sores and, in extreme cases, this leads to gangrene requiring amputation. In the digestive system, scarring can cause acid reflux, along with poo extremes – alternating bouts of constipation and diarrhea. Scleroderma can even affect our sex lives. Men who suffer often experience erectile dysfunction whereas in women, it can cause constriction of the vagina.

But scars can also be a thing of beauty. In fact, in many cultures, including ours, people intentionally scar their bodies. Scarification is a common practice among aboriginal populations in Africa and New Zealand, who cut or brand their skin in decorative designs. For men, the scars intensify their appearance, which comes in handy in battle. But they are also used as a means of attracting women. (Is there no limit to what you guys will do?)

In the US, scarification started cropping up in the 1980s, but it's also slowly spreading across Europe and Australia. It's achieved by cutting or burning into the skin, much like tattooing. And like tattoos, these scars are used as a means of self-expression and can be quite beautiful (and quite scary). Scarification artists even have their own conference, aptly entitled, "Scar Wars."

Scars are friend and foe. They can produce deadly results when they intrude on healthy tissue, but when functioning properly, are a means for the body to heal itself. They are a reminder of our experiences – both good and bad. So flaunt your scars and share your stories; for who wants a perfect body, anyway?

Post Script: I borrowed this blog title from one of my favorite bands' (Theory of a Deadman) CD. Gotta love the beautiful transverse fracture of the humerus.