health and medicine question #379



Ann, a 12 year old female from the Internet asks on May 7, 1998,

Q:

What does the epiglottis do?

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the answer

Gordon Handford answered on May 7, 1998, A:

We have a common tube for both breathing and swallowing/vomiting, the larynx. As breathing is by far, at least for most of us, the more common activity, the relaxed state of the passageway is for the breathing passages to be open. When we breathe in, air enters the nose, passes into the larynx at the back of the nose and throat, goes through the open glottis, down the trachea and into the lungs. When we exhale, the reverse takes place. When you swallow anything, therefore, you must have a way of closing off this air passage or the food/liquid would enter the lungs with the consequence of drowning you or plugging the lungs. Likewise, if you vomited, that material would just as likely enter the lungs as go out your mouth.

Here's where the epiglottis comes in. The epiglottis is a nifty little lid for the larynx (that's the top part of the tube leading to the lungs that also contains the vocal cords that allow us to talk or sing.) The epiglottis is shaped like a toilet lid, and is normally (when you're breathing) held in the half-open position. It is made of a flexible yet somewhat stiff elastic cartilage so that it can be moved to close the opening to the larynx (the glottis) when you swallow or vomit. The flexibility allows it to nicely seal the passage. It is covered with a thin, moist "skin" that contains lots of taste buds on its inner surface.

This way it can tell if some food or liquid has snuck by and can produce violent coughing to clear this material out of the air passages. The really neat thing about how it closes is that it is just like closing a toilet seat, but instead of putting the lid down, you hold the lid still and pull the toilet up! The epiglottis is fixed in place at its upper surface. When you swallow, muscles attached to the larynx pull it upward, making a seal with the epiglottis. Try putting your finger on your Adam's apple (one of the components of the larynx) when you swallow. You will feel it rise, closing off the glottis. Just so you know, the epiglottis is positioned exactly backwards to the position of a toilet seat when you face the toilet, that is, its higher, open end is at the back.

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