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What Are the Ossicles?

The ossicles are the three small bones of the middle ear.
When sound enters the ear, it vibrates the eardrum.
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  • Written By: Mary McMahon
  • Edited By: O. Wallace
  • Last Modified Date: 16 October 2014
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Ossicles in general are very small bones. When people use this word, they are usually referring to the auditory ossicles, the smallest bones of the body. All mammals have ossicles which make up an important part of the system which allows them to hear. Absence of the ossicles will not necessarily result in deafness, but it can cause hearing impairment. Likewise, damage to the bones acquired later in life can also damage the sense of hearing.

There are three ossicles, known formally as the incus, malleus, and stapes. People often refer to these bones with their common names, the anvil, hammer, and stirrup. The names reflect the shapes of the these bones. For perspective, the ossicles found in the human ear are generally small enough to fit comfortably inside one of the number keys on your keyboard, although they can vary slightly in size between individuals.

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The system through which these bones work is rather ingenious. When sound enters the ear and vibrates the eardrum, the movement vibrates the malleus, which is attached to the eardrum. The malleus in turn vibrates the incus and then the stapes, which transmits the vibrations into the inner ear. The ossicles act to amplify the vibration to make it stronger, allowing people to discern sounds better than they could without these bones in place. While it is possible for sound to travel from the ear drum to the inner ear without the ossicles, it will be weaker and harder for the ear to interpret.

However, the ossicles are not designed to vibrate completely at will. They are controlled with muscles which can limit the vibration of the bones if a sound is too loud. Extremely loud noises have the potential to damage the ear if the ossicles are allowed to vibrate freely. The muscle control ensures that they will not vibrate too much. Even with this protection, it is possible for the hearing to be impaired with loud noises, which cause pressure waves that can interfere with hearing. Likewise, pressure waves caused by explosions and other events can also hurt the ears.

These bones can be damaged by severe infections and cancers which penetrate the middle ear. There have also been cases in which people have had hearing damage as a result of blows to the ear or head which damage the interconnected systems of the ear. Such damage can result in a temporary ringing sensation which resolves eventually, or long term damage caused by serious injuries.

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anon281667
Post 6

I was kneed in the left side of my ear and every time I go deep under water it hurts, Could the bones in my ear be damaged?

amysamp
Post 3

@speechie - From what I remember from my audiology 101 course that I had to take back in undergrad (I can’t believe how long ago that’s been now!) the fluid in your ear is behind your tympanic membrane (another word for your eardrum) and therefore around your ossicles, which are located behind the tympanic membrane as well.

This is why the fluid can damage your eardrum.

My fun trivia fact (the ear is full of them): You are most likely to have ear infections because of the fact given by @Saraq90.

Because the Eustachian tube is at a different angle to the middle ear (where the fluid is) when you are a child the ear does not drain as well!

Speechie
Post 2

When I have ear infections, I know there is fluid in my ear, which is obviously going to affect my hearing. My question is the ear infection fluid around my ossicles or is the fluid in my ear canal?

My fun trivia for this subject is that the ossicles are the smallest bones in the human body!

Saraq90
Post 1

For those of you in classes that are learning about these bones, and may need at some point to say the word "stapes" out loud, I would like to go ahead and warn you about its pronunciation.

It is "stay-peez" not "stayps". I have no idea why I thought it was pronounced like that, but I had just read the word before class and not heard it and before that I had just referred to that bone as the stirrup bone.

I've also learned in the class another fun fact for those of you who like trivia games: your eustachian tube (which extends out of the middle ear where your ossicles are) changes shape as you get older!

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