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 (hammer, anvil, and stirrup) of the middle ear. Read below ossicles function.
When the sound waves vibrate the eardrum (the eardrum), it, in turn, shifts the closest ossicular, the hammer to which it is attached. Then malleus transmits vibrations, through the anvil, to the stapes, and thus eventually to the oval window membrane (fenestra ovalis), the opening to the inner ear vestibule. The sound moving in the air is usually reflected in contact with the liquid medium; only about 1/30 of the sound energy moving in the air will be transferred to the liquid. This is observed after sudden cessation of the sound that occurs when the head is submerged under water.
This is due to the fact that the relative 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 were transferred 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.
However, the range of ossicular movements is controlled (and narrowed) by two attached 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.
The bone cubes are in order from the eardrum to the inner ear (from superficial to deep): malleus, incus, and stapes, terms which in Latin are translated as “hammer, anvil, and stirrup”.
Malleus connects with the coil through the heel-dorsal joint and is attached to the eardrum (tympanic membrane) from which the vibratory movement of sound pressure passes.
Incus is connected with both other bones.
The staple is connected to the urethra by arthritic-joint joints and is attached to the fenestra window membrane, an oval or elliptic window or an opening between the middle ear and the inner ear vestibule. It is the tiny bone in the body.