The ear has three sections: the outer ear, the middle ear and the inner ear. Within the middle ear are three tiny bones called the ossicles, which are held in place by two minute muscles. The three middle ear bones--the malleus, incus and stapes-- are the smallest in the human body. They are sometimes collectively called the ossicular chain. The ossicles transmit and amplify the vibrations caused by sound waves from the eardrum to the inner ear.
Malleus: The Hammer
The malleus is the first of the ossicles in the middle ear. It is also known as the hammer because of its resemblance to that tool. The malleus has four parts: the head, neck, handle and the short process. The handle and short process are attached to the eardrum, which is how the vibrations of the eardrum are transmitted to the bones of the middle ear. The malleus is held in place by the tensor tympani muscle.
Incus: The Anvil
The incus is commonly called the anvil. It is sits between the malleus and the stapes and is connected to them by tiny ligaments. The incus has three parts: the body, long process and short process. The body is connected to the malleus, and the long process is connected to the stapes.
Stapes: The Stirrup
The stapes is the smallest bone in the human body. Because of its striking resemblance to the metal loops into which horseback riders place their feet, it is also known as the stirrup. The stapes has four parts: the head, neck, crus and footplate. The footplate fits into the oval window, an opening between the middle and inner ear. The stapes is held in place by the stapedius muscle, the smallest muscles of the human body. The stapedius muscle protects the inner ear from potential damage caused by sudden loud noises by preventing excessive movement of the stapes bone.
References
- "Essentials of Otolaryngology, Fifth Edition"; Frank E. Lucente, M.D., Gady Har-El, M.D., Ari J. Goldsmith, M.D., Neil M. Sperling, M.D., Jon B. Turk, M.D., Editors; 2003
- Johns Hopkins Medicine: How the ear works
- American Speech-Language-Hearing Association: How hearing and balance work
- "Grant's Atlas of Anatomy, Tenth Edition"; Anne M. R. Agur, Ph.D., Ming J. Lee, M.D., John C. Boileau Grant, M.D., Editors; 1999
