All About Ears
Listen. Do you hear that? Whatever it is — the hum of a computer, the birds outside, a car going by — you can hear it and tell which direction it's coming from thanks to your ears.
Hearing is their main job, but it's not all your ears do. They also help you keep your balance, and if pierced in a safe and sanitary manner, they can be an interesting place to show off your fashion sense.
There's a lot more to an ear than what you see on the side of your head. In fact, what you're seeing is only the outer ear, one of three parts of the ear. Hidden from view, but equally important, are the middle ear and inner ear. These complex structures process sounds and transmit signals to the brain.
Your ears work together to gather and process multiple sounds at a time. They also tell you where a sound is coming from and how far away it is.
Our ears are delicate organs that need care and protection. Sounds that are too loud can damage the ears and lead to hearing loss. Unsafe piercings can lead to painful infections.
Knowing how your ears work and what things can affect them will help you better understand your amazing ears and the job they do.
Basic Anatomy of the Ears
Our ears have three different sections that work together to collect sounds and relay them to the brain:
The part of the ear that is visible on the side of your head is called the pinna (also called the auricle). It's made of tough cartilage covered by skin. The pinna's main job is to gather sounds and funnel them to the ear canal, which leads to the middle ear. The pinna includes the earlobe, the part that people pierce to wear earrings.
The ear canal, the hollow passage that leads to your eardrum, is also part of the outer ear. Glands in the skin lining your ear canal produce earwax, which protects the canal by cleaning out dirt and helping to prevent infections.
The middle ear is an air-filled cavity about the size of a pea. The purpose of the middle ear is to turn sound waves into vibrations and deliver them to the inner ear. The middle ear is separated from the outer ear by the eardrum (medical name: tympanic membrane). This thin, cone-shaped piece of tissue stretches tight across the ear canal.
In order for people to hear properly, the pressure on both sides of the eardrum needs to be equal. You probably notice when pressure is out of sync as you go up or down in an airplane. Changes in elevation like this can lead the air pressure to change, and you may feel a popping sensation as your ears adjust.
The reason your ears are able to adjust and maintain equal pressure is because of a narrow tube called the Eustachian tube. This tube connects your middle ear to the back of your nose and acts as a sort of pressure valve, opening to keep the pressure equalized on both sides of the eardrum.
It's in the middle ear that you'll find the three smallest bones in the body. Located just past the eardrum, they're collectively known as the ossicles:
- the malleus (Latin for "hammer"), which is attached to the eardrum
- the incus ("anvil"), which is attached to the malleus
- the stapes ("stirrup"), which is attached to the incus and is the smallest bone in the body
The inner ear consists of tiny organs called the cochlea and the semicircular canals. The snail-shaped cochlea acts as a sort of microphone, converting the vibrations from the middle ear into nerve impulses that travel to the brain along the cochlear nerve, also known as the auditory nerve. The brain then interprets these sounds so we know where they are coming from and what they are.
The semicircular canals look like three tiny, interconnected tubes sticking out in loops from the top of the cochlea. It's their job to help you balance. The canals are filled with fluid and lined with tiny hairs. When your head moves, the fluid in the canals sloshes around, moving the hairs. The hairs send this position information as impulses through the vestibular nerve to your brain. The brain interprets these impulses and sends messages to the muscles that help keep you balanced.
When you spin around and stop, the reason you feel dizzy is because the fluid in your semicircular canals continues to slosh around for a while, giving your brain the idea that you're still spinning even when you aren't. When the fluid stops moving, the dizziness goes away.
The cochlear (auditory) nerve, which sends sound information to the brain, and the vestibular nerve, which carries balance information to the brain, are collectively known as the vestibulocochlear nerve, or 8th cranial nerve.
How We Hear
What's a Sound?
When something vibrates, it makes a sound. Most of the sounds we hear and interpret are vibrations in air (but they can happen in other gases, and in liquids or solids).
When an object or thing vibrates, it flexes in and out. Flexing out pushes the object against the air molecules around it. These molecules in turn push against the molecules next to them. The vibration created travels outward in this manner, much like a ripple or wave. This is a process called compression.
Flexing in while vibrating creates a drop in air pressure that pulls nearby air molecules toward an object. This, in turn, creates another drop in pressure that pulls in the surrounding air molecules, and so on. This process is called rarefaction.
These waves of fluctuation (change) in air pressure — compression and rarefaction — are what we hear as sounds.
Detecting Where Sounds Come From
When a sound wave reaches the ear, it's corralled by the pinna and directed into the ear canal. The pinna, through its distinctive shape and curves, helps people determine the direction a sound is coming from. Sounds coming from different places bounce off the pinna differently. The brain can recognize the difference and decide if the sound is coming from in front or behind.
The two pinnae (plural of pinna) of a person's left and right ears work together to determine if a sound is coming from the right or left. A sound that's coming from the right reaches the right eardrum sooner than the left. It also sounds slightly louder in the right ear. The brain compares the input from both ears and uses this to decide which side the sound came from.
Once inside the ear canal, sound waves vibrate the eardrum, which is very sensitive. The tensor tympani muscle that's attached to the eardrum keeps it taut. So the entire eardrum vibrates no matter where it is hit by a sound wave. This allows the eardrum to detect even the slightest fluctuations in air pressure.
As the eardrum is moved back and forth by the compressions and rarefactions of sound waves, the ossicles move, too. The movement of these tiny bones transmits and amplifies sound waves into the cochlea.
The Ear 'Talks' to the Brain
The cochlea is filled with fluid and contains thousands of tiny fibers. These fibers — which are short and stiff in some areas and longer and more flexible in others in order to decipher frequencies (pitches) — detect movement of sound waves.
When sound waves travel into the cochlea, they reach the fibers and give off a burst of energy. This burst of energy is detected by something called the organ of corti, a structure that lines the cochlea and contains thousands of tiny hair cells. When energy is released, it's strong enough to move these hairs.
The organ of corti sends an electrical impulse to the brain telling it which hairs (and how many) were moved. This information helps the brain's cerebral cortex determine the pitch and volume of a sound. So, for example, when a person hears a loud sound, it's because a stronger burst of energy affected more of the hairs in the organ of corti.
Things That Can Go Wrong
Given the outer ear's exposure to the elements and the middle ear's connection to the nose via the Eustachian tube, more than a few things can affect the ear and bring on hearing loss. Fortunately, most of these conditions can be treated effectively if they're detected early by a doctor.
Some of the more common ear problems include:
Noise-induced hearing loss (NIHL). This hearing loss is brought on by too much exposure to loud noise. Loud noises can damage the hair cells in the cochlea. For kids in America, one of the main culprits is portable music players. Video games, TVs, movie theaters, traffic, power tools, and even some appliances can also be too noisy for most people. NIHL can also be caused by a one-time exposure to a very loud sound such as an explosion or thunder clap. NIHL is almost 100% preventable if you take steps to protect your ears.
Otitis media. This infection of the middle ear is the most common cause of hearing loss in children. It can affect one or both ears and happens when pus and mucus build up behind the eardrum if the Eustachian tube gets blocked by allergies or a cold or upper respiratory infection. Otitis media, if left untreated, can damage the eardrum, causing hearing loss and an infection of the mastoid bone behind the ear.
Otitis externa. Also known as "swimmer's ear," this infection of the outer ear happens when water and bacteria get trapped in the ear canal. The bacteria can multiply in the warm, moist environment, leading to irritation and infection of the skin lining the ear canal. This is called "swimmer's ear" because it's a common problem for swimmers, but it can affect anyone who bathes or takes a shower.
Tinnitus. A ringing, humming, buzzing, roaring, or clicking in the ears is known as tinnitus. It happens as a result of damage to nerve endings in the inner ear. In young people, the main cause of tinnitus is exposure to loud noises. Medical treatments or hearing devices can often help people who have tinnitus.
Impacted earwax. Earwax, also known as cerumen, traps dirt and dust before they reach the eardrum. Usually, earwax dries and falls out of the ear or is washed away. But in some people it can build up and plug the inside of the ear canal (known as "impaction") and cause hearing loss. Fortunately, doctors and nurse practitioners can usually treat this kind of hearing loss simply by washing away the wax. Because earwax can get impacted, doctors recommend never using cotton swabs in the ear canal because doing this can push wax deeper into the ear canal and make it harder to get out.
Ruptured eardrum. A puncture or rupture of the tympanic membrane is known as a ruptured or perforated eardrum. Ruptured eardrums are sometimes accompanied by pain, discharge from the ear, and decreased hearing. Ruptured eardrums can often heal on their own, but sometimes people need surgery to repair the rupture. Things can get serious if water gets into the middle ear. So if you have a ruptured eardrum, your doctor will tell you how to protect your middle ear from water and bacteria while it heals.
Cholesteatoma. This is a type of skin cyst that affects the middle ear. Someone can be born with cholesteatoma, but usually it's a complication of untreated otitis media. If the Eustachian tube isn't working properly, it can cause negative pressure in the middle ear. This pulls the eardrum into the middle ear, creating a cyst or pocket that can fill with dead skin cells and other waste material and become infected. People who have cholesteatoma need to get surgery to remove the cyst. If it's not treated, it's possible for the infection to spread to the brain, causing more serious problems like meningitis.
Meniere's disease. Meniere's disease causes problems with balance and hearing. It occurs when a part of the semicircular canals called the endolymphatic sac becomes swollen. This affects the movement of the fluid in the canal and sends an incorrect signal to the brain regarding body position and balance. Episodes of Meniere's disease, which can produce severe dizziness, can happen without warning. Some people get them a lot, others as rarely as once a year. Doctors don't know exactly what causes Meniere's disease, and it can't be cured. But there are treatments and things people can do to help relieve symptoms.
Injuries, burns, and frostbite. Exposed to the elements as they are, your ears are subject to all manner of minor injuries. Usually that's no big deal, but an injury to the outer ear or ear canal can lead to bleeding and infection that may affect other parts of the ear. A direct blow to the ear, such as from a car accident or sports injury, may tear the eardrum, dislocate the ossicles, or damage the inner ear. Repeated hits to the outer ear can cause bruising and blood clots that disrupt blood flow to the cartilage of the pinna and damage its shape and structure. This is a condition called "cauliflower ear."
Piercing problems. If you decide to pierce your ears, go to reputable, trained practitioners in clean, sanitary surroundings. Because piercing breaks the skin, there's always a risk of infection. To protect against germs, use a cotton ball or swab to apply rubbing alcohol or antibiotic ointment to the earlobe around each earring. Rotate earrings at least twice a day to keep the holes open while they heal. Pierced earlobes generally take about 6 to 8 weeks to heal. Pierced ear cartilage takes 4 months to a year to heal completely.
Protecting Your Ears
There's an old saying about how you should never stick anything in your ear except your elbow. It's meant to be funny, but there's a kernel of truth to it. Sticking things like cotton swabs and fingernails into your ears can scratch the ear canal, push earwax deeper into your ear, and even rupture your eardrum. If you find yourself having trouble removing earwax from your ear canal, seek a doctor's help.
Protecting your hearing is mostly a matter of common sense. Start by turning down the volume on your car stereo and TV and especially on your portable music player. If you know you will be exposed to loud noises, such as at a concert, car race, or construction site, bring protection for your ears in the form of earplugs or protective earmuffs.
If you notice problems with your hearing, get tested by a doctor right away. You may not be able to recover lost hearing, but if hearing loss is treated early, the damage can be limited.
Hearing damage accumulates over the years. But it doesn't take as long as you'd think for problems to develop. Tiny earbuds can harm your hearing as much as a large chainsaw — by damaging the tiny hairs in the cochlea. Keep this in mind when you reach to turn up the volume, and your hearing will be yours for decades to come!
Reviewed by: Steven Dowshen, MD
Date reviewed: June 2011
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