The auditory ossicles are the malleus (hammer), the incus (anvil), and stapes (stirrup). These are small bones in the middle ear. How small are these auditory ossicles? One source says they are no bigger than an orange seed.
What these little bones do is form a chain that connects the eardrum to the inner ear, where the cochlea is. The first one in the chain is the malleus, the next one is the incus, and the last one is the stapes. The chain has a job to do: When the eardrum vibrates from sound input, it makes the auditory ossicles vibrate too. The vibrations move through the chain and the stapes transmits the sound through the oval window (an opening covered by a membrane) and into the fluid of the cochlea. Then the rest of the hearing mechanism takes over.
Some diseases impact the auditory ossicles and affect a person's ability to hear. One of these is otosclerosis, a disease in which bone growth prevents the ossicles from being able to do their job. That can result in hearing loss.
How We Hear. American Speech-Language-Hearing Association. http://www.asha.org/public/hearing/How-We-Hear/. Accessed May 2011.
I Love What I Hear. National Institute on Deafness and Other Communication Disorders. http://www.nidcd.nih.gov/health/education/teachers/hearing.html. Accessed May 2011.