Take a breath. Exhale. Repeat. Hold back your breath for a while if you want to but not for too long, because the oxygen must keep coming. It has to get to every one of our several trillion (twelve zeroes) cells steadily. The cells can’t break down food molecules without it. That would be like our eating dinner without having the stomach acid to digest it; no nourishment. When we die, it’s because, for one reason or another, the oxygen no longer gets to our cells, and they starve.
Reading about how our breathing works, I was surprised by some of the proportions of oxygen involved. For starters, only about twenty percent of the air around us that we pull in to our lungs is oxygen. The rest is nitrogen and a percent or two of carbon dioxide and other gasses. And we don’t use even very much of that oxygen that we do pull in. Only about a quarter of it goes into our blood. While the air we inhale is twenty percent oxygen, the air we exhale is still fifteen percent oxygen. Still, that five percent difference is the oxygen that keeps us alive. In the course of one day, in total volume, it would about fill the trunk of a large sedan.
The oxygen that stays in our lungs must cross the thin membrane of the lung itself to the blood stream on the other side before it can go to work. Gasses, including oxygen, move away from the location where they are the most densely packed to wherever they are less dense, (just as smoke will spread steadily from its source into the air around it). The oxygen in the lung is much denser than any oxygen left in the blood cells flowing in the veins nearby. Those blood cells have already dropped off their previous oxygen at cells around the body. Oxygen, because of its arrangement of electrons, is, as some would say, a very “friendly” gas. It readily combines with many other elements. So the incoming oxygen easily crosses the membrane to the oxygen-depleted blood and hooks up with a hemoglobin molecule in a blood cell.
As the oxygenated blood flows to, say, the fingers, and passes near cells that have used up their bit of oxygen to energize themselves, the incoming oxygen detaches from the hemoglobin and crosses cell membranes to take part in the cell’s digestive chemistry. Meanwhile, instead of making the return trip empty, the blood picks up the carbon dioxide left over from the cell metabolism and drops it off at the lung for exhaling.
People have long spoken and written about “the breath of life” and about breath as spirit. But after learning in some detail about how the body distributes oxygen, I’m thinking that it’s not the air or the oxygen itself that is so wondrous. It is the breathing of it, the body itself that pulls in the oxygen in an endless rhythm, that sets up the conditions for it to move across membranes, and distributes it to a million million cells. In the right amounts. Every instant while we’re alive.