The Parts of the Ears

The Parts of the Ears
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  • 0:00 Your Ears
  • 0:27 External Ear
  • 1:19 Middle Ear
  • 2:53 Internal Ear
  • 4:27 Lesson Summary
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Lesson Transcript
Instructor: Rebecca Gillaspy

Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

Your ears are made up of three main parts, the external ear, middle ear, and internal ear. Sound waves move into your external ear causing the eardrum to vibrate, which moves the tiny bones of your middle ear, and then it's on to the internal ear.

Your Ears

Everyone in your family, including your pets, hear through their ears. Of course, your ears and your dog's ears look quite different, but when you look below the surface, the parts of the ear are the same. In this lesson, we will learn about the structures inside the three major divisions of the ears, namely the external ear, middle ear, and internal ear.

External Ear

The external ear is where hearing begins and is shaped somewhat like a funnel. It consists of the pinna, also known as the auricle, which is the most noticeable part of the external ear, as well as the external auditory canal, which is the tube that carries the sound waves inward. This canal is also where that gooey earwax is produced. The external ear's funnel-like shape helps it do its job, which is air conduction. In other words, the external ear captures sound waves traveling through the air and funnels them inward.

Air passing through the external auditory canal bumps up against the tympanic membrane, or eardrum. This is a membrane that vibrates when struck by sound waves. It marks the division between the external ear and the middle ear.

Middle Ear

When sound waves hit the tympanic membrane, it vibrates, causing the ossicles, which are three tiny bones within the middle ear, to move. Each ossicle has a nickname based on its appearance. The malleus is commonly referred to as the hammer; the incus as the anvil; and the stapes as the stirrup.

The vibrating eardrum causes a chain reaction of movement that gets passed along from the hammer to the anvil to the stirrup. The moving stirrup then pushes up against the oval window, which marks the division between the middle and internal ear. So we see that in the middle ear, the transfer of sound waves occurs through bones. Therefore, the middle ear's function is to conduct sound through bone conduction.

Now, before we leave the middle ear, I want to mention one of the interesting structures, the Eustachian tube. This is the tube that connects the middle ear to your throat.

Did you ever get an ear infection after having a sore throat? That happened when the throat infection spread up the Eustachian tube and caused an inflammation of the middle ear. While this makes the Eustachian tube seem like a problem, it actually serves a valuable purpose. Did you ever fly in an airplane and find it hard to hear until you swallowed causing your ears to pop? Swallowing opens the Eustachian tube and equalizes the pressure in the middle ear to match the changing atmospheric pressure as your plane climbs up into the sky.

Internal Ear

Okay, let's get back to the conduction of sound. Once the stirrup taps on the oval window, we find ourselves inside the internal ear. Here, we find the bony labyrinth, which is a bony, fluid-filled structure within the internal ear. It has three subdivisions: the cochlea, the vestibule, and the semicircular canals.

The cochlea looks like a curled-up snail shell. It contains many tiny cells that are lined with even smaller extensions that look like hairs under a microscope. These tiny hairs are the hearing receptors. The repeated tapping of the stirrup against the oval window, causes the fluid in the internal ear to move over top of these hairs. This generates a nerve impulse that's carried by the cochlear nerve to your brain where the sound is interpreted. So, we see that the function of the internal ear is to carry out sensorineural conduction, which is the conduction of sound through nerve impulses.

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