How you hear
The ear is made up of the outer ear, the middle ear and the inner ear. Find out about the parts of the ear and what each part does.
Parts of the ear
The ear has three main parts. These parts include the outer ear, the middle ear and the inner ear. Each section is made up of structures that play a role in changing sound waves into signals that go to the brain.
Outer ear
The outer ear is made up of the part of the ear that you can see, called the pinna (PIN-uh), and the ear canal. The cup-shaped pinna picks up sound waves from outside the ear and sends them into the ear canal.
Middle ear
The middle ear is an air-filled space, called a cavity, that holds a chain of three bones. These bones include:
- The hammer, also called the malleus.
- The anvil, also called the incus.
- The stirrup, also called the stapes.
The eardrum lies between these bones and the outer ear. Also called the tympanic membrane, the eardrum vibrates when a sound wave strikes it.
A narrow channel called the auditory tube links the middle ear to the back of the nose and upper part of the throat. This channel also is called the eustachian tube.
The tube opens and closes at the throat end to keep the pressure in the middle ear the same as the pressure outside the ear. The pressure needs to be equal on both sides for the eardrum to work as it should. The tube also drains fluids.
Bones of the middle ear
The middle ear has a chain of three tiny bones in it. They are:
- The hammer, also called the malleus. It’s attached to the eardrum.
- The anvil, also called the incus. It’s in the middle of the chain of bones.
- The stirrup, also called the stapes. It’s attached to the membrane-covered opening called the oval window that connects the middle ear with the inner ear.
The bones send vibrations from the eardrum to the inner ear. The three bones differ in size, shape and position. This causes the force of the vibration to rise, called amplify, by the time it gets to the inner ear. This rise in force helps transfer the energy of the sound wave to the fluid of the inner ear.
Inner ear
The inner ear holds a group of linked fluid-filled chambers. The snail-shaped chamber, called the cochlea (KOK-lee-uh), plays a role in hearing. Sound vibrations from the bones of the middle ear transfer to the fluids of the cochlea.
Tiny sensors lining the cochlea, called hair cells, turn the vibrations into electrical impulses. The impulses go along the auditory nerve to the brain. This is where damage and hearing loss due to age, loud noises or medicine begin.
The other fluid-filled chambers of the inner ear include three tubes called the semicircular canals. The three bony canals lie at right angles to each other. They respond to motions of the head.
Hair cells in the semicircular canals feel the motion of the fluid when you move. The hair cells change the motion into electrical signals. The signals travel along the vestibular nerve to the brain. This gives you your sense of balance
Traveling to the brain
Electrical impulses travel along the auditory nerve and pass through many brain centers that process information. Signals from the right ear travel to the auditory cortex. The auditory cortex is in the temporal lobe on the brain’s left side. Signals from the left ear travel to the right auditory cortex.
The auditory cortices sort, interpret and file information about the sound. This process lets you detect certain sounds. It also lets you block other sounds as background noise.
Feb. 25, 2025
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