Stomaching the Digestive Process
Published: Friday, February 15, 2013
Updated: Friday, February 15, 2013 00:02
When you walk into a room full of Nalgene-toting gym addicts getting their sweat on during a late afternoon Yates workout, what is the first thing that comes to mind? You’re probably wondering how they can keep up all of that cardio crunching and thigh burning, but I bet you haven’t stopped to consider how their bodies are responding to such a significant fluid loss with perspiration or how they can possibly turn sips of Gatorade into life-bringing fuel for the next round of Ab Ripper X. Interested in hearing more? I’ll start with the basics and see if I can teach you a thing or two about this incredible thing you’re living and breathing in all day, every day: water.
As you may have guessed, I’ll start with the mouth, the opening to what is a continuous tube called the gastrointestinal tract that transforms perfectly delicious food and beverage into that stuff nobody ever really wants to talk about: you guessed it, poo. Let’s say for the sake of this mini-lesson that you’re at Tombs chowing down on a juicy hamburger and enjoying the perfect complement of your favorite ale. When you swallow, everything moves down the esophagus through the highly acidic environment of your stomach, and into the small intestine, where the cells lining the inner walls happily absorb the electrolytes and proteins from the now-digested morsels of hamburger. Accompanying this whole process is the concurrent movement of beer-turned-water from within the intestine through the very same layer of cells we talked about earlier and into your circulatory system.
This is where all the fun begins. Gone are the distasteful sights, sounds and smells of the digestive tract; here to stay, at least until a change of pace occurs with urine excretion, are the dark recesses of your blood vessels. A water molecule of microscopic proportions, is herded into an onrush of free-floating particles, antibodies, proteins and red blood cells quickly heading to the pumping chambers of the heart. As the water molecule is propelled through the oxygenating conditions of the lungs, back into the left heart, and upward through the aorta, what once was a solitary flowing river is quite rapidly giving rise to numerous streams branching off in all directions. The crisscrossing paths of arteries and veins daze and confuse, but no need to fret: After a few missed turns and a little backtracking, the water molecule will eventually happen upon its final destination, the kidneys.
It is helpful to imagine the kidneys as the body’s security force, guaranteeing liberty and justice for all within the chaos of the blood stream. They do their job well — kind of like the TSA with its exacting attention to detail at Reagan or Dulles — effectively filtering from the circulation anything that might damage other organs. They are also the sites of vitally important regulation of blood volume and a balanced concentration of electrolytes in the plasma, concentrating urine when the fluid in the body is hypotensive, or low volume, and diluting urine when there is plenty of fluid.
And so your journey ends, from a faucet in a local watering hole to the pot, the john or, as we in D.C. like to call it, the Oval Office. Cool, but what does all of this have to do with those sweaty undergrads at the gym? The short answer: quite a bit. Stay tuned for the next health talk to hear more on exercise, sports drinks and America’s love affair with hydration.
David Sterns is a student at Georgetown University School of Medicine. ALMOST-DOCTOR DAVE appears every other Friday in the guide