Chapter 2: The Nose: The First Gate

More Than a Bump on Your Face

Look in a mirror and find your nose. It sits right in the middle of your face, a little bump with two small holes at the bottom. You use it every day without giving it much thought. But your nose is one of the busiest and cleverest parts of your whole body.

Your nose is the main front door for the air you breathe. Most of the time, when you are calm and resting, air enters your body through your nose. Your mouth can let air in too, and it is a useful back door when you need a lot of air quickly. But the nose does special work that the mouth cannot do nearly as well.

In the last chapter, you learned that air carries tiny travelers such as dust, pollen, smoke and germs. Your nose is the first gate those travelers meet. Like a gate in a castle wall, the nose lets in what the body needs and does its best to keep out what the body does not need.

The nose does at least four important jobs. It catches dust and germs. It makes the air warm. It makes the air damp. And it smells the air to warn you about danger. In this chapter, you will learn about each of these jobs, one at a time.

Try this. Close your mouth and breathe in slowly through your nose. Notice how the air feels as it enters. Now breathe out through your nose and feel the warm air on your upper lip. In that one quiet breath, your nose has already done all four of its jobs.

Two Doors and a Wall

The two holes at the bottom of your nose are called nostrils. Each nostril is a doorway that leads into a hollow space behind your nose. This hollow space is called the nasal cavity. It is much bigger than you might think. It stretches back from your nostrils all the way to the top of your throat.

Down the middle of the nasal cavity runs a thin wall. This wall is called the septum. The septum divides the inside of your nose into a left side and a right side. Near the front, the septum is made of a firm but bendy material called cartilage. You can feel cartilage if you gently wiggle the tip of your nose or the top of your ear.

Here is a surprising fact about your two nostrils. They usually do not let in the same amount of air at the same time. For a few hours, one side of the nose is a little more open, and the other side is a little more closed. Then the two sides slowly switch. Many people never notice this at all.

You can check this safely right now. Hold the back of your hand just under your nose and breathe out gently through your nose. You may feel a stronger puff of air from one nostril than from the other. Scientists think this switching gives each side of the nose a little time to rest and refresh its lining.

The walls inside your nose are covered with a soft, pink, wet layer called the lining. The lining has many important jobs, and you will learn about most of them in this chapter. It is delicate and needs to be treated gently. That is one reason why it is never a good idea to poke things into your nose.

Your nasal cavity also has neighbors. Inside the bones of your face, around your nose and behind your forehead and cheeks, there are hollow spaces filled with air. These spaces are called sinuses. Each sinus is connected to the nasal cavity by a small opening. The sinuses are lined with the same kind of wet lining as the nose, and the mucus they make drains into the nose. In children, some of the sinuses are still small, and they keep growing as the face grows.

Hairs That Catch Dust

Just inside your nostrils, you can find small, stiff hairs. These are your nose hairs. They might not look important, but they are the first guards that air meets on its way into your body. They stand at the doorway like the bristles of a doormat.

Think about a doormat at the front of a house. When people step on it, the bristles catch mud and little stones from their shoes. That way, less dirt gets carried inside the house. Your nose hairs do something very similar for air. As air rushes past them, the hairs catch larger pieces of dust, sand, pollen and even tiny insects.

Nose hairs work best on bigger things. Very small bits, like germs and the tiniest specks of smoke, can slip between the hairs. That is fine, because the nose has other ways to deal with them. The hairs are simply the first layer of protection, and many more layers are waiting farther inside.

The hairs grow from the skin just inside the nostril, the same way the hair on your head grows from the skin on your scalp. They grow slowly, fall out from time to time and are replaced by new ones. Grown-ups sometimes trim long nose hairs that stick out, but the nose always keeps plenty of hairs to do the job.

Deeper inside the nose, there is a different kind of hair that is far too small to see. These hairs are called cilia. They are so tiny that thousands of them could fit on the head of a pin. You will learn more about cilia soon, because they work together with something very sticky.

Mucus: The Sticky Trap

The lining of your nose makes a slippery, sticky liquid called mucus. You might know mucus by other names, and you probably notice it most when you have a runny nose. But mucus is not just something messy. It is one of the most important guards your body has.

Mucus works like flypaper or sticky tape. When dust, pollen and germs fly into your nose, many of them bump into the wet lining and get stuck in the mucus. Once they are stuck, they cannot travel farther into your body. The mucus holds on to them so that they can be carried away.

Mucus does more than just trap things. It also contains special substances that can weaken or break apart some kinds of germs. It contains antibodies, too. Antibodies are tiny helpers made by the immune system that grab on to germs and mark them as enemies. So mucus is not just a trap. It is a trap with guards living inside it.

Your nose makes mucus all day and all night, even when you are perfectly healthy. Most of it you never see. That is because of the tiny cilia you read about. The cilia stand up from the lining like a field of grass, and they wave back and forth over and over, very fast. Together, they push the layer of mucus slowly toward the back of your nose.

From the back of your nose, the mucus slides down into your throat, and you swallow it without noticing. That might sound strange, but it is a clever plan. The mucus and everything stuck in it go down into your stomach. Your stomach is full of strong juices that destroy most germs. So the germs caught in your nose end up being broken down far away from your lungs.

The mucus is always moving, like a slow conveyor belt in a factory. New, clean mucus keeps being made at the front, and old mucus full of dust and germs keeps being carried away at the back. The whole layer is replaced many times each day. Your nose is always cleaning itself, even while you sleep.

Have you ever noticed that your nose runs when you cry? There is a reason for that. Your eyes are always making a thin layer of tears to keep them clean and wet. A tiny tube carries used tears from the inner corner of each eye down into your nose. When you cry, so many tears flow that the extra tears pour into your nose, and your nose starts to drip.

When you catch a cold, your nose makes much more mucus than usual. The extra mucus helps wash the germs out, a little like a stream washing away fallen leaves. That is why your nose runs during a cold. It can be annoying, but it is your nose working hard to protect you. Blowing your nose gently into a tissue helps clear the extra mucus away.

Sometimes the lining of the nose also swells up during a cold, and the inside of the nose feels blocked or stuffy. The swelling happens because extra blood flows into the lining to bring more helper cells to the place where germs are. When the germs are gone, the swelling goes down again, and breathing through the nose becomes easy once more.

Warming and Wetting the Air

Your lungs are delicate and they like air to be warm and damp. Cold, dry air can make the lining of the breathing passages sore and can make it harder for the guards there to do their work. So before air reaches your lungs, your nose does a second job. It turns cold, dry air into warm, damp air.

How does a nose warm the air? The lining of your nose is full of tiny blood vessels. Blood is warm, because it carries heat from inside your body. As air passes over the lining, heat from the blood moves into the air. It is a little like holding cold hands near a warm cup. The warmth flows from the cup into your hands.

Your nose also makes air damp. The wet lining gives some of its water to the air as the air moves past. By the time air has traveled deep into your lungs, it is close to the temperature inside your body, and it is full of moisture. This is true even on a freezing winter morning.

Your nose also helps when you breathe out. The warm, damp air leaving your lungs passes back over the lining near the front of your nose, which is a little cooler. Some of the warmth and water in that air goes back into the lining. In this way, your nose saves some of the heat and moisture that would otherwise be lost, so it has more to give to the next breath coming in.

To do this work well, the nose needs to slow the air down and spread it out. Inside each side of your nose, there are three curved shelves of bone covered with lining. These shelves stick out from the outer walls of the nasal cavity, one above another. They make the air swirl and tumble as it passes, so that more of the air touches the warm, wet lining.

The swirling air helps with catching dust and germs, too. When air tumbles around corners, the heavier bits flying in it cannot turn as quickly as the air does. They bump into the wet lining and stick there. It is like a car going around a sharp bend too fast and ending up in a soft pile of sand at the side of the road.

When you breathe through your mouth instead, the air skips much of this warming, wetting and cleaning. That is why your throat can feel dry and scratchy after a long time of breathing through your mouth, for example when your nose is stuffy during a cold. Breathing through your nose, when you can, gives your lungs the gentlest and cleanest air.

Because the lining of your nose has so many blood vessels close to the surface, a nose sometimes bleeds. This can happen if the nose is bumped or if the air is very dry. A nosebleed can look surprising, but it is common in children. If it happens, stay calm and tell a grown-up, who will know how to help.

Smell: The Nose's Alarm Bell

Your nose has one more job that no other part of your body can do. It smells. High up inside the nasal cavity, near the top, there is a small patch of special lining on each side. This patch holds millions of smell cells. When air swirls up to this patch, the smell cells check the air for scents.

Everything that has a smell sends tiny bits of itself floating into the air. When you smell fresh bread, tiny bits from the bread have drifted through the air and into your nose. The smell cells catch those bits and send a message to your brain. Your brain reads the message and tells you, that is bread.

Some animals have an even stronger sense of smell than people do. A dog has many, many more smell cells than a person, and a much larger part of its brain is used for understanding smells. That is why a dog can follow the trail of a smell that a person cannot notice at all. Still, the human nose is very good at its own job, which is helping you enjoy the world and keeping you safe from smells that mean danger.

People can tell apart thousands of different smells. Flowers, rain on dry ground, oranges, soap, a warm blanket from the dryer and a favorite meal all have their own scents. Smells can even bring back memories. A certain smell might remind you of a holiday, a grandparent's kitchen or the first day of school.

Smell is also an alarm bell. Some smells warn you that something might hurt you. The smell of smoke can tell you that something is burning. The sour smell of milk that has gone bad tells you not to drink it. A rotten smell from old food warns you to stay away from germs that might be growing on that food.

The gas used in some stoves and heaters has no smell of its own. So a strong, unpleasant smell is added to it on purpose. That way, if any gas leaks out, people notice the smell and can get away from it. If you ever smell something like gas or smoke at home, tell a grown-up right away.

Your sense of smell does not work very well as an alarm while you are asleep. A sleeping person may not wake up because of a smell, even a strong one. That is why many homes have smoke alarms on the ceiling. A smoke alarm makes a loud noise that can wake people up, so the alarm does the job that a sleeping nose cannot do.

Smell also helps you taste. When you eat, smells from your food float up from the back of your mouth into your nose. Much of what you think of as the flavor of food really comes from smell. That is why food can seem to taste flat when your nose is blocked during a cold. When the cold is over, the flavors come back.

Being Kind to Your Nose

Your nose works hard for you, so it is good to treat it kindly. When your nose is runny, blow it gently into a tissue. Blowing too hard can hurt your ears or make your nose sore. Blow one side at a time if that feels easier, and throw the tissue away when you are done.

After you blow your nose, wash your hands with soap and water. Remember that mucus holds germs. If those germs stay on your fingers, they can spread to toys, door handles and other people. Washing your hands keeps the germs from traveling. It also means that your nose's hard work catching germs is not wasted.

Your nose also does its best work when your whole body is cared for. Drinking enough water during the day helps every part of your body, including the wet lining inside your nose. Getting plenty of sleep gives your guards time to rest and rebuild. Playing outside in fresh air, away from smoke, gives your nose cleaner air to work with.

Try not to pick your nose. Fingers carry germs, and fingernails can scratch the delicate lining inside. A small scratch can let germs in and can make the nose bleed. If your nose feels itchy or full, a tissue is the best helper. And never put small objects such as beads, buttons or tiny toys into your nose, even as a joke.

Your nose can only catch so much at one time. Sometimes something gets past the nose hairs and the mucus, or tickles the lining in just the wrong way. When that happens, your body does not wait around. It has a fast and powerful way to throw unwanted things out. You have done it many times. It often starts with a tickle, then a deep breath in, and then a loud and sudden ah-choo.

That sudden blast of air is a sneeze. A sneeze, along with its close partner the cough, is one of your body's emergency exits. In the next chapter, you will find out how sneezes and coughs work, why they are so fast and why it matters so much where you aim them.

Key Words

Nostrils: The two openings at the bottom of your nose. Air enters your nose through the nostrils.

Nasal cavity: The hollow space behind your nose where air is cleaned, warmed and made damp. It reaches back to the top of your throat.

Septum: The thin wall that divides the inside of your nose into a left side and a right side.

Cartilage: A firm but bendy material found in your nose and ears. It is softer than bone.

Nose hairs: Small, stiff hairs just inside your nostrils. They catch larger bits of dust and pollen like a doormat catches dirt.

Mucus: A sticky, slippery liquid made by the lining of your nose and breathing passages. It traps dust and germs and contains helpers that fight germs.

Cilia: Tiny hairs, too small to see, that wave back and forth very fast. They move mucus along like a conveyor belt.

Antibodies: Tiny helpers made by the immune system. They grab on to germs and mark them so the body can destroy them.

Smell cells: Special cells high up inside the nose that sense scents in the air. They send messages about smells to the brain.