Montshire Minute: Human Lungs

Originally aired during the week of October 9, 2000

Monday

You do it thousands of times a day, without even thinking about it. Breathing does two important things: it supplies the blood stream with oxygen, and it expels carbon dioxide. Oxygen, which makes up about 20 percent of our atmosphere, is drawn into the lungs when you inhale. When you exhale, you're getting rid of carbon dioxide. Breathing is involuntary, but we can't do it by simply by keeping our mouths open and waiting for the air to filter into our lungs. We need a way to pull the air inside. We do this with the help of our diaphragm, a sheet of muscle below the lungs that rhythmically expands and contracts. When you breathe in, the diaphragm lowers, which allows the lungs to expand. When you breathe out, the diaphragm rises, and carbon dioxide is released. There is always some air left in lungs when we exhale.

Tuesday

Your lungs get plenty of protection - they are surrounded by the rib cage, the breastbone, and respiratory muscles. The lungs need this protection because they play such a vital role in our bodies' moment-to-moment functioning. Each day we breathe in and out about 5,000 gallons of air, which contain the oxygen we need to survive. Air drawn in through the trachea passes through the two main tubes the lead into the lungs themselves. The air is carried through thinner and thinner passages, which finally terminate in air sacks called alveoli. The alveoli are laced with capillaries, networks of tiny blood vessels with walls so thin that gases like oxygen can pass right through. There are 3 million or so of these capillary networks, and it is here that the oxygen actually enters the bloodstream. The pumping action of the heart then carries the oxygen to cells throughout your body.

Wednesday

Your lungs are delicate, spongy organs each about the size of a football. A moist membrane layer covers the lungs and also the inside of the chest cavity. The lubricated surfaces of these membranes help the lungs inflate and deflate smoothly, without sticking to each other. Are you completely grossed out yet? Ok, so take a deep breath and we'll move on. As we saw in yesterday's program, networks of tiny capillaries in the lungs transfer oxygen into the bloodstream. Well these capillaries also deliver carbon dioxide moving in the other direction - from the body's tissue back to the lungs. When you exhale, you are emptying your lungs of carbon dioxide and preparing to breathe in more oxygen. At rest, you take about 15 breaths a minute, with perhaps a pint of air moving in and out of the lungs.

Thursday

At rest, we may breathe 15 times a minute, taking in about a pint of air each time. But our lungs are capable of taking in a much greater volume when we are exercising. For short periods of time, your body may even use up oxygen faster than your lungs and heart can replace it. But nature has provided our muscles with the ability to incur a short-term oxygen debt. When we pant or gasp for air after we finish exercising, we are repaying that debt. Breathing is involuntary - we do it without thinking--because bringing oxygen into the body is such a vital and ongoing task. A stubborn child can stop himself from breathing for a while. If he threatens to hold his breath until he gets his wish, his face may even turn three shades of purple. But he'll never expire from lack of oxygen. Sooner or later the breathing instinct will take over.

Friday

It is said that yawning is a sign of fatigue or boredom. Another common explanation is that we yawn when our bodies need more oxygen. Long periods of shallow breathing may leave us somewhat oxygen deprived, and yawning is a way to gulp in more air. But more recent research is less certain about that. Next time you feel a yawn coming on, try to keep your mouth closed and breathe through your nose. Pretty much impossible, huh? If yawning is simply the body's way of taking in more oxygen, you still should be able to breathe through your nose. We seem to yawn and stretch at the same time, so yawning may be a way of stretching the head and neck. Whatever the cause of it, researchers have noted that yawning can be a contagious thing. Hey, maybe just listening about yawning can be set you off. Or... YAWN... talking about yawning...