The ossicles are the bones in the ears that allow us to hear. They are, by far, the smallest bones in the body. All three of the ossicles fit into a cavity in the skull about the size of a dime. The ossicles transmit sound between the external and inner ear by conducting mechanical vibrations. The tympanic membrane, or eardrum, converts sound into mechanical vibrations that then travel though the ossicles to the small oval window of the inner ear. In the inner ear, the vibrations stimulate hearing receptors and allow the brain to perceive sound.
Malleus
The malleus is the first bone after the eardrum. It has two finger-like projections that attach to the eardrum and a body that articulates with the incus, another ossicle. This complex shape allows it to transmit sound as vibrations from the eardrum to the incus.
Stapes
The stapes is a U-shaped bone with a flat base. This base attaches to the oval window of the inner ear and transmits the vibrations from the incus to the fluid in the inner ear. This is the smallest bone of the body and is light enough to efficiently transmit even high frequencies between the external environment and the inner ear.
Incus
The incus is an L-shaped bone that magnifies the vibrations between the malleus and stapes by mechanical means. Because the lengths of each arm of the L are different, the vibration from the eardrum is magnified before it is transmitted to the stapes.
References
- "Gray's Anatomy: The Anatomical Basis of Clinical Practice"; Susan Standring; 2008
- Netter Images: External Ear and Tympanic Cavity
