Chapter 4: The Throat and Tonsils: Guards at the Crossroads

The Crossroads Behind Your Mouth

Open your mouth wide in front of a mirror and say a long "ahh." Look past your teeth and your tongue, all the way to the back. You will see a pink wall and, above it, a soft arch hanging down. That pink wall is the back of your throat. It is one of the busiest places in your whole body.

Your throat is a tube that runs down behind your nose and your mouth. Its real name is the pharynx. In a grown-up, the pharynx is a little shorter than a new pencil, and in a child it is shorter still. It begins high up behind your nose and ends low in your neck, where it splits into two separate tubes.

The pharynx has three parts, stacked one on top of another. The top part sits behind your nose, where the air you breathe through your nose arrives. The middle part sits behind your mouth, the part you can see in the mirror. The bottom part sits lower in your neck, just above the place where the tube splits in two.

What makes the throat so special is that two very different things pass through it. Air passes through it every time you breathe. Food and drink pass through it every time you swallow. The air is on its way to your lungs. The food and drink are on their way to your stomach. For a short part of their journeys, they both use the same road.

That is why the throat is like a crossroads in a busy town. Roads come in from the nose and from the mouth. Roads go out toward the lungs and toward the stomach. Travelers of all kinds pass through all day long. And as you learned in Chapter 1, some of those travelers are germs.

A crossroads where so many travelers meet needs guards. Your body has placed several guard posts right around your throat. These guard posts are called the tonsils and the adenoids. Before you meet them, though, it helps to know a little about the wet and busy place where they live.

A Wet and Busy Place

The inside of your throat is covered with a smooth, wet lining, much like the lining inside your nose. This lining is tough enough to handle food sliding past it many times a day. It also makes mucus, which keeps the throat slippery and catches some of the dust and germs that pass by.

Your mouth helps too. Your mouth makes a watery liquid called saliva, which you may also call spit. Saliva keeps your mouth and throat wet, so that talking and swallowing are easy. Over a whole day, a grown-up's mouth makes roughly enough saliva to fill a large water bottle. You swallow almost all of it without noticing.

Saliva is not just water. Like the mucus in your nose, saliva carries special substances that can weaken some germs. It also carries antibodies, the tiny helpers you met in Chapter 2 that grab on to germs. And saliva is always flowing, so it keeps washing your mouth and the back of your throat, the way a gentle stream keeps rinsing the stones in its bed.

Saliva starts the work of breaking down your food, too. If you chew a piece of plain bread for a long time, it may start to taste a little sweet. That happens because saliva begins to break down the starch in the bread into sugar. So saliva helps you eat and helps protect you at the same time.

Your mouth makes much less saliva while you sleep. That is why your mouth can feel dry and sticky when you first wake up in the morning. During the day, when you talk, chew and eat, saliva flows freely again. Even the smell or the thought of a favorite food can make your mouth water, which means your body is getting ready to eat.

Remember the mucus from your nose, which slowly slides toward the back? This is where it ends up. It drips gently down the back of your throat, along with the dust and germs stuck in it, and you swallow it with your saliva. All of these travelers go down to your stomach, where strong juices destroy most of the germs.

Look again at the soft arch at the back of your mouth. Hanging down from the middle of it, you may see a small, soft piece of flesh shaped a bit like a drop of water. It is called the uvula. The uvula is part of the soft roof at the back of your mouth, which you will read more about at the end of this chapter.

Meet Your Tonsils

Now look on either side of the back of your mouth, just behind the soft arch. In many children, you can see a rounded, pink lump on each side. These two lumps are your tonsils. They are about the size of a grape or a little smaller, though their size is different from person to person.

Your tonsils may look like nothing much, but they are guard posts of your immune system. Remember that the immune system is your body's team of special cells and body parts that find and fight germs. The tonsils are one of the places where that team keeps watch.

If you could look at a tonsil up close, you would see that its surface is not smooth. It is covered with small pits and folds, like a sponge or a walnut. These pits make the surface of the tonsil much bigger than it looks from the outside. A bigger surface means more room to catch and check the germs that come past.

Inside each tonsil live huge numbers of white blood cells. White blood cells are the soldier cells of your immune system. They travel around your body and gather in guard posts like the tonsils, where they wait for germs to arrive. There are several kinds of white blood cells, and each kind has its own special job.

The tonsils sit in exactly the right place. Every bit of food you swallow and every breath you take through your mouth passes right by them. That means the tonsils get an early look at many of the germs that enter your body. They are like guards standing at the side of a busy road, watching every traveler who walks by.

The tonsils have one more trick. When germs arrive, the tonsils can call for help. They send out signals that bring even more white blood cells rushing to the throat. It is like a guard at a gate ringing a bell so that other guards come running. The more germs there are, the more helpers arrive.

But the tonsils do more than watch. They take small samples of the germs that pass by and pull those samples into their pits. Then the white blood cells inside study the samples. In this way, the tonsils help your body find out which germs are around and what those germs look like. You will learn why this matters later in this chapter.

The Hidden Guards and a Ring of Posts

The tonsils you can see are not the only guard posts at the crossroads. Higher up, behind your nose, where you cannot see them even with a mirror, there is another clump of guard tissue. It is called the adenoids. The adenoids sit at the very top of the throat, right where the air from your nose arrives.

The adenoids do the same kind of work as the tonsils, but they watch a different road. The tonsils watch what comes in through the mouth. The adenoids watch what comes in through the nose. Together, they make sure that germs entering by either road are noticed early.

Near the adenoids, there are two small openings, one on each side. Each opening leads to a narrow tube that runs up to the inside of one ear. These tubes let air move between your throat and your ears. Have you ever felt your ears pop when you yawn or swallow? That pop is air moving through these little tubes to balance the pressure inside your ears.

There is even more guard tissue at the back of your tongue, low down where the tongue curves toward the throat. These patches are sometimes called the tongue tonsils. You cannot see them easily, but they are there, watching food as it slides toward your throat.

If you could see all of these guard posts at once, you would notice that they form a ring around the top of your throat. The adenoids are at the top of the ring, the tonsils are on the sides, and the tongue tonsils are at the bottom. Any germ entering through the nose or the mouth must pass through this ring of guards.

Think of an old walled town with watchtowers. There is a watchtower on every side, so no matter which road a traveler takes into the town, a guard in one of the towers can see the traveler coming. The ring of guard posts in your throat works in a similar way. Every road into your body passes close to one of the towers.

The tonsils and adenoids are usually biggest when children are young. That makes sense, because young children are meeting many germs for the very first time, and their guard posts are very busy learning. As children grow into teenagers, the tonsils and adenoids often become smaller. The body keeps many other ways to protect itself, so smaller guard posts are not a problem.

How the Guard Posts Learn About Germs

Here is one of the most amazing things about your immune system. It can learn. When it meets a germ for the first time, it does not yet know the best way to fight that germ. But it studies the germ carefully, and it gets ready. The next time the same germ shows up, your body can often fight it much faster.

The tonsils and adenoids are some of the places where this learning happens. When a sample of a germ is pulled into a tonsil, special white blood cells look at its shape. Every kind of germ has its own shape on the outside, a little like every key has its own pattern of bumps and grooves.

Once your white blood cells know the shape of a germ, some of them begin to make antibodies that fit that shape exactly. An antibody is like a key that fits only one lock. When antibodies find a germ with the matching shape, they stick to it. A germ covered in antibodies has trouble getting into your cells, and it is easier for other white blood cells to find and destroy it.

After the germ is defeated, some of the white blood cells that learned its shape stay in your body for a long time. They are called memory cells. Memory cells are like guards who keep a picture of a troublemaker pinned to the wall. If that troublemaker ever comes back, the guards recognize it right away and sound the alarm.

The tonsils and adenoids are connected to the rest of your immune system by a network of very thin tubes. These tubes carry a clear liquid called lymph. Along these tubes, there are small bean-shaped lumps called lymph nodes. Lymph nodes are more guard posts, where white blood cells gather and check the lymph for germs. You have many lymph nodes in your neck, close to your throat.

When your body is fighting germs, the lymph nodes in your neck can get bigger and a little tender. Grown-ups sometimes call them swollen glands. The swelling happens because many white blood cells are crowding into the lymph nodes to do their work. When the fight is over, the lymph nodes usually shrink back to their normal size.

So the guards at the crossroads are part of a much bigger team. The tonsils and adenoids watch the roads and take samples. The lymph nodes check the lymph. Memory cells remember old enemies. All of them pass messages to one another, so that your whole body can be ready when germs arrive.

You may wonder why, if the immune system can remember germs, people still catch colds again and again. The answer is that there is not just one cold germ. There are hundreds of different viruses that can cause a cold, and each one has its own shape. Each time you catch a cold, your body may be meeting a new one for the first time. Over the years, your immune system builds up a bigger and bigger collection of memories.

When the Throat Gets Sore

Sometimes germs settle in your throat and make it sore. A sore throat can feel scratchy or painful, especially when you swallow. Many sore throats are caused by viruses, the same kind of germs that cause colds. Some sore throats are caused by bacteria.

A sore throat is often one of the first signs of a cold. You might wake up one morning with a scratchy throat, and then a runny nose and a few sneezes follow later in the day. The sore throat is a sign that your guards have noticed the germs and have started their work. In many colds, the soreness gets better after a few days as the guards win the fight.

When germs settle in the throat, the tonsils often get bigger and redder. That is because more blood and more white blood cells rush to them to fight the germs. The tonsils are doing their job, but the swelling can make the throat hurt. It is a bit like a crowded guard post where everyone is rushing around at once.

If your throat feels sore, tell a grown-up. A grown-up can keep an eye on how you are feeling and decide whether to talk to a doctor. This is especially important if swallowing is very hard, if breathing seems difficult, or if you feel very unwell. Doctors know how to look at a throat and find out what kind of help, if any, is needed.

Sometimes doctors decide that a child's tonsils or adenoids should be taken out, for example when they cause problems again and again. You might know someone who has had this done. People can stay healthy without their tonsils or adenoids, because the body has many other guard posts that do the same kind of work.

Most of the time, though, the tonsils and adenoids simply do their work quietly, year after year. They watch the roads, take their samples and help your immune system learn. You do not feel them working at all. They are a small but important part of the team that keeps you healthy.

A Choice at the Crossroads

Now think again about the crossroads. Air and food both pass through your throat. But at the bottom of the throat, the road splits in two. One road, in front, leads down to your lungs. The other road, behind it, leads down to your stomach. Air needs to take the front road, and food and drink need to take the back road.

Your body has to make sure that every traveler takes the right road. It does this with several clever movements that happen every time you swallow. One of these movements happens high up, near the uvula you saw in the mirror. When you swallow, the soft roof at the back of your mouth lifts up and closes off the space behind your nose. That stops food and drink from going up into your nose.

Have you ever laughed so hard while drinking that a little drink came out of your nose? That can happen because you laughed at the same moment you were swallowing. The laugh pushed air and drink upward before the soft roof could close the way. It is surprising and a bit funny, but it shows how carefully your body usually keeps the roads apart.

An even more important guard stands at the split in the road, right above the entrance to your lungs. It is a small flap shaped like a leaf. Every time you swallow, it tips down like a little door and covers the opening to your breathing tubes. That way, food and drink slide past it into the road toward your stomach.

This little door is called the epiglottis. You swallow hundreds of times every day, and the epiglottis does its job almost every single time. In the next chapter, you will meet the epiglottis up close. You will learn how it keeps food out of your lungs, what happens when something goes down the wrong way and how you can help it do its job.

Key Words

Pharynx: The real name for the throat. It is a tube behind the nose and mouth that carries both air and food.

Saliva: The watery liquid made in your mouth. It keeps your mouth wet, starts breaking down food and helps wash away germs.

Uvula: The small, soft piece of flesh that hangs down at the back of the roof of your mouth.

Tonsils: Two rounded lumps at the back of the mouth, one on each side. They are guard posts of the immune system that check germs entering through the mouth.

Adenoids: Guard tissue high up at the back of the nose, where you cannot see it. The adenoids check germs entering through the nose.

White blood cells: The soldier cells of the immune system. They find germs, help the body learn about them and destroy them.

Memory cells: White blood cells that remember the shape of a germ the body has fought before. They help the body fight that germ faster next time.

Lymph nodes: Small, bean-shaped guard posts along thin tubes that carry a clear liquid called lymph. Many of them are in your neck.

Epiglottis: A small flap shaped like a leaf that covers the entrance to the breathing tubes each time you swallow.