Bone cubes (also called ossicles) are three bones in the middle ear that belong to the smallest bones in the human body. They are used to transfer sounds from the air to a fluid-filled labyrinth (snail). Lack of hearing blocks would be moderate to severe hearing loss.

 

The term “ossicle” literally means “tiny bone”. Although the term may refer to any small bone in the entire body. It usually refers to the hammer, anvil, and stapes of the middle ear. Read below ossicles function.




ossicles function

When the sound waves vibrate the eardrum, it shifts the closest ossicular, the hammer malleus to which it is attached. Then hammer malleus transmits vibrations, through the anvil.  The stapes and thus eventually to the oval window membrane, which opening to the inner ear vestibule.

 

The sound moving in the air usually reflect in contact with the liquid medium, only about 1/30 of the sound energy moving in the air will transfer to the liquid. This is observed after a sudden cessation of the sound that occurs when the head is submerged under water.

 

Ossicles function

 

This is due to the causes that the comparative incompressibility of a liquid is a resistance to the strength of sound waves traveling in the air. Bone cubes give a mechanical advantage to the barrel by lever action and reduction of the force distribution area.

 

The resulting vibrations would be much weaker if the sound waves transfer directly from the outer ear to the oval window. This reduction in the area of force application allows a sufficiently high-pressure increase to transfer most of the sound energy to the liquid.

 

The increased pressure will compress the fluid in the cochlea and transmit the stimulus. Thus, the presence of ossicles to focus the vibration strength improves the sensitivity to sound and is a form of impedance matching.

 

ossicular movements

However, the range of ossicular movements control (and narrowed) from two attach muscles (timpani tensor and stapedius). These muscles are thought to shrink to suppress auditory oscillations to protect the inner ear from excessively noisy noise and to give better frequency resolution at higher frequencies by reducing low-frequency transmission. These muscles are more developed in bats and serve to block outgoing bats screaming during echolocation.




Ossicles structure

The bone cubes are in order from the eardrum to the inner ear (from superficial to deep). The malleus, incus, and stapes, terms which in Latin translate as “hammer, anvil, and stirrup”.

 

Ossicles function

 

Malleus connects with the coil through the heel-dorsal joint. It is attached to the eardrum (tympanic membrane) from which the vibratory movement of sound pressure passes. Incus connect with both other bones.

 

The staple connects to the urethra with arthritic-joints. It attaches to the fenestra window membrane, so oval or elliptic window or an opening between the middle ear and the inner ear vestibule. It is the tiny bone in the body.