In short, an intact body preserved in formaldehyde is systematically opened to inspect organs, muscles, nerves, and blood vessels, literally from head to toe.A top concern of the premedical student is contemplating his tolerance of the sometimes gruesome process of dissection. Early in the semester we, too, split off into groups of four for each cadaver and nervously peeked within the black body bags, the pale lifeless body covered by a damp cloth. But it's true, one becomes quickly inured to the frankness with which we (respectfully) explore the body.
Dissection is a long process, taking roughly 3-4 hours three days a week over a dozen weeks, resulting in roughly four hundred hours total. Each day's dissection covers a specific part of the body - we might study the rib cage and the lungs one day and the heart another. Slowly we move throughout the body, placing organs in plastic bags and exposing muscles until what remains is a far cry from the intact human at the beginning of the term. Fat is an ever present barrier, and indeed much of the day is spent digging through preserved globules of fat for items of interests (one of HST's groups had the fortune of dissecting a cadaver with virtually no visible body fat, which incidentally allows them to complete dissections more quickly). I therefore often find myself questioning the utility of dissection as we spend 20 minutes trying to distinguish the glossopharyngeal nerve from the vagus nerve in the neck and ultimately discovering that we nicked the glossopharyngeal earlier. In a three hour dissection, we could have potentially memorized far more than we discovered in the body that day.
Indeed, some medical schools are dispensing with cadaver dissection altogether and moving to an electronic modeling system. Arguably having a three-dimensional representation vividly memorized in one's head is as practically useful as seeing it on an actual body.
Yet there are some moments of profound discovery that redeem every last hour on the dissection. One came early when I cut the connections of the right lung to the body, lifted it out of the body, and held it in my hand, spongy and surprisingly heavy. A perforation of the lining of the lung - from a stab wound, say - would immediately collapse it, preventing air from entering. Bacteria can infiltrate them quite easily and build up fluid in the lungs. Yet it otherwise functions perfectly every normal day, supplying crucial oxygen throughout our bodies, without which we would die within minutes.
Another moment came from dissection of the arm and hand. Consider for a second all the possible motions of each finger. With your fingers outstretched and palm up, you can move your fingers left, right, up, down; curl and uncurl them; and all combinations of these. Think about what a complex task typing on a keyboard is, moving multiple fingers to precise locations in sync over and over again.
Each individual motion of the finger is controlled by a single muscle, such that operation of the hand requires over a dozen muscles. Yet the anatomy of the hand makes perfect sense. By pulling on the specific muscle, I could make each finger move according to the muscle's function. This reminded me of a very complex marionette, with an overseer rapidly pulling strings to make me type an email. The overseer is the brain, and when we recently cut out the brain from the cadaver's skull and held it in our hands, I realized that this pale, spongy mass was responsible for our recognition of our existence and all subsequent behaviors. Somewhere in this dense mess, neurons were connected with each other such that we could actually reason theoretically and make extraordinarily complex decisions. Yet you break open the skull or put a bullet through it, and that can all disappear. The brain begins to die irrecoverably from lack of oxygen within 5 minutes.
Dissection and anatomy have taught me a vast body of material that may be practical in the future. But more powerfully, it has also made me appreciate simultaneously the human body's complexity and fragility. I think it is a wonder that such a complex being resulted from gradual improvements from microbes, even if it took a billion years. That a spinal cord the thickness of a quarter can relay messages from the spongy mass of the brain and control millions of processes in the body is still astounding to me.
Knowledge of human anatomy is arguably more important in some specialties - surgery, radiology, pathology - than in others - anesthesiology, medical oncology. But a respect for the body is indispensable in all.
very good post
ReplyDeleteI was never ever able to do my dissections.
in fact i never touched a boy till my 2nd year