bjones
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Surprisingly, scientists don’t fully understand yawning. We know that everyone does it. Even babies who have not been born yet have been observed yawning in the womb. Animals yawn too. Why do we yawn? That’s where the problem starts. We have some theories of why people yawn, but none of them has ever been proven. Some scientists believe that we don’t breathe deeply enough when we are tired. The body compensates for it by taking in a long, deep breath to bring up the oxygen levels in the blood. This sounds like a reasonable explanation, but, so far, tests don’t show that increasing oxygen reduces yawning. The reverse is also true. Reducing oxygen intake has never shown to increase yawning.
Another theory about why people yawn is that it is a way for the lungs to stretch themselves. People also stretch when they are tired. Yawning flexes the muscles around the lungs and pulling in a lot of air, stretches out the lungs themselves. In theory, this stretching is supposed to increase the heart rate and make us feel a little more awake.
Yet another theory states that yawning helps to protect the lungs reflexively by distributing surfactant throughout the airways. Surfactant is an oily substance that the lungs need to stay lubricated. The oily lubrication keeps the walls of the airways from sticking to each other, closing them up.
One strange fact about yawning is that it is contagious. People cannot control when they will yawn, but somehow when we see someone yawning, something in our brain is triggered to make us yawn too. In one study, 60 percent of people will yawn just from watching someone else yawn on TV.
 Posted 5355 day ago
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