Notes

After being filtered, moistened and warmed, the air travels further down the airway. It passes your pharynx, the area at the back of your throat, which is a passageway for food, liquids as well as air. The lower part of your pharynx diverges into your windpipe and your oesophagus. It goes without saying that air must go down the windpipe and food and liquids down the oesophagus! When you swallow food, the opening to your windpipe must be closed; otherwise you might suffocate. How does this happen? When you swallow food or liquids, a thin plate of flexible cartilage called the epiglottis moves down and closes the windpipe. This means you cannot swallow and speak at the same time! If you try to do this anyway, your epiglottis will not close the windpipe completely, with dangerous consequences.

Have you ever had a drink come out through your nose because you were laughing and trying to swallow at the same time? There is an opening between the nasal cavity and the pharynx so that you are able to breathe through your nose. Another small flap behind your throath called the uvula closes the nasal cavity when you swallow. With the combined help of the uvula and the epiglottis, food or liquids have only one way down: the oesophagus (figure 1.4). But don’t laugh or talk and swallow simultaneously or they will not work!

The temperature of the air that enters your nose is usually lower than your body temperature. Cold air can dry out the mucus lining of your respiratory system, and this can make you ill. This means that the air you inhale must be warmed up. This air is warmed up by blood, running through tiny blood vessels in the lining (walls) of your nasal cavity.

Look at figure 1.2. What do you notice? That’s right, the lining of the windpipe and bronchi look moist. The lining of your your respiratory system, including your nasal cavity, is indeed moist and mucous (slimy). When you breathe in through your nose, the mucus in the nasal lining moistens the air you inhale.

Air contains all kinds of dust particles, pollen and germs that can make you ill. Therefore, the air you inhale must be filtered. Nose hairs inside your nostrils, filter the large particles out of the air you inhale. The smaller particles and germs get trapped by mucus in the nasal lining and in the linings of your windpipe and bronchi. This mucus is then swept to your pharynx by ciliated cells (see figure 1.3). The mucus can now enter the oesophagus, where it is swallowed.

The olfactory cells high up in your nasal cavity check the air for the presence of chemicals that form odours. If an odour is recognised by the brain as dangerous or bad-smelling you can respond by walking away from this odour.

Your oral cavity does not contain any hairs or ciliated cells, nor does it contain a lot of mucus.

After passing the pharynx, air enters your larynx. Inside the larynx are your vocal cords or vocal folds (figure 1.5): two elastic folds of tissue that stretch across the windpipe, just below the epiglottis. They are joined at the front of the larynx and extend to the rear of the windpipe. When you exhale you can produce sounds because the passing air causes the vocal cords to vibrate. Because of this is the larynx also called the voice box.