What is the Incus?

Also known as the anvil, the incus is one of the small bones found in the middle ear. It works in conjunction with two other small bones, the malleus and the stapes, to relay sound from the middle ear to the inner ear. This tiny bone is only found in mammals.

The incus is positioned between the malleus and the stapes. In actual function, the bone serves as a connection that receives the sound waves captured by the malleus, then transmits that sound to the stapes. Since the stapes is located at the oval window of the inner ear, the sound is then transmitted into the inner ear. As long as these three bones are not damaged or there is no infection in the inner ear, they are capable of properly transmitting sound for the entire life span of an individual.

There are several conditions that can impact the incus's ability to function. One has to do with an ear infection. When the infection is based in the middle ear, the sound received by the malleus and transmitted to the incus is muffled. Because the transmission is inferior, the sound that the bone transfers to the stapes is also of lower quality. The end result is that the individual is unable to detect sounds at certain pitches or levels. Usually, full function is restored once the middle ear infection is successfully treated.

A second issue that can impair the function of this bone is trauma to the middle ear that is severe enough to damage the bone itself. Trauma of this type may occur as the result of an accident, such as an auto crash or a fall from a high place. It is also possible to cause damage to these three bones in the middle ear during the course of warfare. Examples of this type of damage include trauma sustained as a result of shrapnel that comes in contact with the bone structure surrounding the ear, or even during hand to hand combat. Essentially, any trauma that is severe enough to jar the incus out of position has the potential to partially or completely prevent the bone from functioning properly.

The name of this tiny but important bone is actually a Latin word that corresponds to the word anvil in English. This designation is appropriate, since the shape of the incus is very similar to that of the anvil that was once commonly used in the creation of horseshoes and other forms of ironwork. In fact, it is the shape of the bone that makes it ideal for the reception and transmission of sound waves on the journey to the inner ear.