Merck Manual

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Reviewed/Revised May 2022 | Modified Sep 2022
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What are the ears?

Ears are one of your sensory organs and have 2 important jobs:

The Ears
  • Hearing

  • Balance

What are the main parts of the ears?

Your ears have 3 main parts:

  • Outer ear

  • Middle ear

  • Inner ear

The outer ear is what you see on the outside of your head. It's a large flap of cartilage that's covered in skin. The tunnel leading into your middle ear is called the ear canal.

The middle ear is made up of the eardrum and a small space filled with air. This space contains 3 tiny bones, named after their shapes. These bones are called the hammer, the anvil, and the stirrup. These tiny bones transmit sound from the middle ear to the inner ear.

The middle ear is connected to the back of your nose by the eustachian tube. This tube helps drain fluid, so it doesn't build up in the middle ear. When you get a cold, this tube can become inflamed (red and swollen), causing an ear infection.

The inner ear is made up of the cochlea and the vestibular system. These structures are filled with fluid and contain sensors that turn sound and motion into nerve signals.

Inside the Ear

Inside the Ear

How do the ears work?

How does hearing work?

Your ears take in sound waves and turn them into nerve signals that travel to your brain. Your brain interprets the signals as sounds, such as a voice or music.

  • Sound waves enter your ears and travel down your ear canal to the eardrum

  • The sound waves make your eardrum vibrate

  • The eardrum's vibrations travel along the 3 small bones of your middle ear

  • The 3rd little bone vibrates part of your inner ear called the oval window

  • Vibrations in the oval window go into the cochlea, which turns the vibrations into nerve signals

  • Nerve signals from the cochlea pass along the auditory nerve to your brain

The cochlea is a spiral-shaped organ full of fluid. Inside the cochlea are thousands of microscopic hairs called cilia that vibrate in response to sound. Different cilia respond to different frequencies of sound. Some respond to low-pitched sound like a drum. Some respond to high-pitched sound like a bell. Others are in between. Your brain can tell which cilia are sending signals, so it knows the pitch of sound that entered your ears.

How does balance work?

A system of tiny sacs and tubes inside your ears helps you keep your balance. These small sacs and tubes are called the vestibular system.

Your vestibular system is filled with fluid and lined with microscopic hairs called cilia.

  • When you move your head, the fluid in your vestibular system moves

  • The moving fluid bends the cilia one way or another

  • The direction the cilia bend causes a specific nerve signal

  • The nerve signals from the cilia pass along the vestibular nerve to your brain

  • Your brain uses the nerve signals to tell which way your head is moving

What can go wrong with the ears?

Problems with the ears include:

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