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The Smallest Bone in the Body
The smallest bone in the body is called the "stapes" . The stapes is located within your ear. Infact it is the third bone in a sequence of bones within the middle ear.
Its name, "stapes" is the latin word for "stirrup". If you look closely at the stapes bones it appear much like a stirrup for horse riding. The main footplate the stapes is attached to the entrance of the inner ear where as the top of the stapes connects to the incus, the next smallest bone in line. Altogether the middle ear has three of the smallest bones. The other two connecting bones are also named after their appearance and shape, attached to the stapes is the incus which means anvil in latin and the bone between the incus and your ear drum is called the malleus which is the latin word for hammer. All three bones together are termed "the ossicles" which means little bones.
Figure 1: Stapes (Grays Anatomy ,1918)
The smallest bone in the body plays a vital role in transmitting sound from the previous bone to the inner ear, conducting sounds to your cochlea and enabling you to hear sounds every moment, everyday. This little bone is able to articulate the way it does with the incus bone due to the incudostapedial joint. A number of attachments meet this little bone such as the stapedius muscle which attaches to the back top of the stapes. Interestingly the stapedious muscle is also noted as being the smallest muscle in the body.
Figure 2: Ear Anatomy (Perception Space:The Final Frontier)
In terms of size the stapes bones measures less than 3mm in size, in comparison to the largest bone in the body which is the femur of an adult male can be 48cm in length. Infact the stapes is the smallest bone in most mammals.
In some cases the smallest bone in the body can become fixated in place, unable to vibrate the way it should. This is called Otosclorosis and can lead to requiring surgery known as a stapedectomy. This involves removing part of the stapes bone with a plastic or metal implant to regain the connection of transmission with the incus bones to follow through to the inner ear.
For further reading:
Harper, Douglas. "Stapes (n.)". Online Etymology Dictionary.
Dispenza, F; Cappello, F; Kulamarva, G; De Stefano, A (October 2013). "The discovery of stapes". Acta Otorhinolaryngologica Italica. 33 (5): 357–9
Lars Chittka; Axel Brockmann - Perception Space—The Final Frontier, A PLoS Biology Vol. 3, No. 4, e137 doi:10.1371/journal.pbio.0030137