Did you hear something? Maybe the sound you heard was as quiet as your cat licking her paws. Or maybe it was loud, like a siren going by. Sounds are everywhere, and you have two cool parts on your body that let you hear them all: your ears!
Your ears are in charge of collecting sounds, processing them, and sending sound signals to your brain. And that's not all — your ears also help you keep your balance. So if you bend over to pick up your cat, you won't fall down — or even worse — fall on your cat. Meow!
The ear is made up of three different sections: the outer ear, the middle ear, and the inner ear. These parts all work together so you can hear and process sounds.
The Outer Ear: Catch the Wave
The outer ear is called the pinna or auricle (say: or-ih-kul). This is the part of the ear that people can see. It's what people pierce to wear earrings and what your friend whispers into when it's time for a secret. The main job of the outer ear is to collect sounds, whether they're your friend's whispers or a barking dog.
The outer ear also includes the ear canal, where wax is produced. Earwax is that gunky stuff that protects the canal. Earwax contains chemicals that fight off infections that could hurt the skin inside the ear canal. It also collects dirt to help keep the ear canal clean. So earwax isn't just gross. It's gross and useful.
The Middle Ear: Good Vibrations
After sound waves enter the outer ear, they travel through the ear canal and make their way to the middle ear. The middle ear's main job is to take those sound waves and turn them into vibrations that are delivered to the inner ear. To do this, it needs the eardrum, which is a thin piece of skin stretched tight like a drum.
The eardrum separates the outer ear from the middle ear and the ossicles (say: ah-sih-kulz). What are ossicles? They are the three tiniest, most delicate bones in your body. They include:
- the malleus (say: mah-lee-us), which is attached to the eardrum and means "hammer" in Latin
- the incus (say: in-kus), which is attached to the malleus and means "anvil" in Latin
- the stapes (say: stay-peez), the smallest bone in the body, which is attached to the incus and means "stirrup" in Latin
When sound waves reach the eardrum, they cause the eardrum to vibrate. When the eardrum vibrates, it moves the tiny ossicles — from the hammer to the anvil and then to the stirrup. These bones help sound move along on its journey into the inner ear.
The Inner Ear: Nerve Signals Start Here
Sound comes into the inner ear as vibrations and enters the cochlea (say: ko-klee-uh), a small, curled tube in the inner ear. The cochlea is filled with liquid, which is set into motion, like a wave, when the ossicles vibrate.
The cochlea is also lined with tiny cells covered in tiny hairs that are so small you would need a microscope to see them. They may be small, but they're awfully important. When sound reaches the cochlea, the vibrations (sound) cause the hairs on the cells to move, creating nerve signals that the brain understands as sound. The brain puts it together and hooray! You hear your favorite song on the radio.
Day or Night, Ears Keep You Upright
Ears do more than hear. They keep you balanced, too. In the inner ear, there are three small loops above the cochlea called semicircular canals. Like the cochlea, they are also filled with liquid and have thousands of microscopic hairs.
When you move your head, the liquid in the semicircular canals moves, too. The liquid moves the tiny hairs, which send a nerve message to your brain about the position of your head. In less than a second, your brain sends messages to the right muscles so that you keep your balance.
Sometimes the liquid in your semicircular canals keeps moving after you've stopped moving. To understand this, fill a cup halfway with water. Now move the cup around in a circle in front of you and then stop. Notice how the water keeps swishing around, even after the cup is still? That's what happens in your semicircular canals when you spin in circles or go on the Tilt-A-Whirl at the amusement park.
When you stop spinning or step off the ride, the fluid in your semicircular canals is still moving. The hairs inside the canals are sensing movement even though you're standing still. That's why you might feel dizzy — your brain is getting two different messages and is confused about the position of your head. Once the fluid in the semicircular canals stops moving, your brain gets the right message and you regain your balance.
Three Cheers for the Ears!
Your ears take care of you, so take care of them. Protect your hearing by wearing earplugs at loud music concerts and around noisy machinery, like in wood or metal shop at school. Keep the volume down on your stereo, especially if you're in the car or wearing headphones.
And one last thing — don't go poking around in your ears, even with cotton swabs. As you probably know, there's only one thing that's safe to put in your ear. Your elbow, of course.
Reviewed by: Robert C. O'Reilly, MD
Date reviewed: October 2009
