By Howard J. Bennett
By the time kids enter middle school, most of them will have experienced the following scene: A bunch of students are sitting in the cafeteria eating lunch. One of them has just taken a sip of milk when another one tells a joke or lets out a juicy fart. The milk drinker starts to laugh but ends up choking because he had just swallowed and the milk was still heading toward his stomach. Then, after a few seconds of sputtering, a river of milk shoots out of his nose.
Anyone who wasn’t drenched in milk thinks this was hilarious, but the episode raised an important question: How does milk make this odd detour out of the body?
People are designed so air, liquids, and solids all past through the back of the mouth on their way south. However, air and food end up in different places. Anything that is headed to the stomach arrives via the esophagus (swallowing tube). Anything that is headed to the lungs uses the trachea (windpipe).
The epiglottis is a flap of elastic cartilage that lies at the top of the trachea. This tissue acts as a sentry of sorts that keeps solids and liquids from getting into your lungs. When something “went down the wrong tube,” that means it touched the epiglottis, which sent the person into spasms of coughing.
If someone swallows milk and laughs at the same time, it may cause liquid to hit the epiglottis. Although this clearly describes why our unfortunate milk drinker began to cough, it does not explain why the milk came out of his nose.
When a person coughs or vomits, the soft palate and uvula are pushed back thereby separating the back of the mouth from the back of the nose (think of it as a door closing). This protective reflex works most of the time, which is why people usually vomit or cough up food through their mouths. The system isn’t perfect, however, which explains why things can sometimes shoot out the nose. It is very uncommon for food to take this path because the nasal passages are so small. For milk and other liquids, however, this can happen more easily—hence all those lunchrooms that serve as launching pads for milk rockets.
So what’s the best way to avoid dousing your school chums in milk? Either stop sitting with kids who tell jokes and fart or make sure to swallow very carefully.
Bonus Fact: The roof of your mouth is made up of the hard and soft palate. You can feel these areas by lifting your tongue and pushing it against the top of your mouth. The uvula is the pink tissue that resembles a punching bag and hangs down from the back of the soft palate.
© 2012 Howard J. Bennett. All Rights Reserved.
(First published in the Washington Post 4/6/09.)
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