Editing Ossicles

{{about|the bones in the human ear|elements embedded in the body wall of echinoderms|Ossicle age = File:Temporal bone - The Hungry Artist Multimedia.jpg 
| Caption     = Auditory ossicles: [[Malleus]], [[incus]] and [[stapes]]
| Width       = 300
| Image2      = Auditory ossicles-en.svg
| Caption2 =  
| PartOf = [[Middle ear]]
|Ossicle (echinoderm)}}
{{short description|Three bones in each middle ear that are among the smallest bones in the human body}}
{{Ear series|expanded=Middle}}
The '''ossicles''' (also called '''auditory ossicles''') are three [[irregular bone]]s in the [[middle ear]] of [[human]]s and other [[mammal]]s, and are among the smallest [[bone]]s in the human body.<!--not *the* smallest; there are many other ossicles that are not counted among the 206 bones listed in anatomy exams--> Although the term "ossicle" literally means "tiny bone" (from [[Latin]] ''ossiculum'') and may refer to any small bone throughout the body, it typically refers specifically to the [[malleus]], [[incus]] and [[stapes]] ("hammer, anvil, and stirrup") of the middle ear.

The auditory ossicles serve as a [[kinematic chain]] to transmit and amplify ([[intensity (physics)|intensify]]) [[sound]] vibrations collected from the air by the [[ear drum]] to the fluid-filled [[labyrinth (inner ear)|labyrinth]] ([[cochlea]]). The absence or pathology of the auditory ossicles would constitute a moderate-to-severe [[conductive hearing loss]].

== Structure ==
{{See also|Malleus|Incus|Stapes}}
[[File:Slide1ghe.JPG|thumb|left|350px|Anatomy of the three ossicles]]
The ossicles are, in order from the eardrum to the inner ear (from superficial to deep): the [[malleus]], [[incus]], and [[stapes]], terms that in [[Latin]] are translated as "the [[hammer]], [[anvil]], and [[stirrup]]".<ref>{{Cite journal |last=Hilal |first=Fathi |last2=Liaw |first2=Jeffrey |last3=Cousins |first3=Joseph P. |last4=Rivera |first4=Arnaldo L. |last5=Nada |first5=Ayman |date=2023-04-01 |title=Autoincudotomy as an uncommon etiology of conductive hearing loss: Case report and review of literature |url= |journal=Radiology Case Reports |language=en |volume=18 |issue=4 |pages=1461–1465 |doi=10.1016/j.radcr.2022.10.097 |issn=1930-0433 |pmc=9925837 |pmid=36798057}}</ref>
* The [[malleus]] ({{langx|en|"hammer"}}) articulates with the incus through the [[incudomalleolar joint]] and is attached to the [[tympanic membrane]] ([[eardrum]]), from which vibrational sound pressure motion is passed.
* The [[incus]] ({{langx|en|"anvil"}}) is connected to both the other bones.
* The [[stapes]] ({{langx|en|"stirrup"}}) articulates with the incus through the [[incudostapedial joint]] and is attached to the membrane of the ''[[fenestra ovalis]]'', the elliptical or [[oval window]] or opening between the middle ear and the [[Vestibule of the ear|vestibule]] of the [[inner ear]]. It is the smallest bone in the body.<ref>{{cite web|url=http://kidshealth.org/kid/htbw/bones.html|title=Your Bones|work=kidshealth.org}}</ref>

=== Development ===
Studies have shown that ear bones in mammal embryos are attached to the [[dentary]], which is part of the lower [[jaw]]. These are ossified portions of [[cartilage]]—called [[Meckel's cartilage]]—that are attached to the jaw. As the embryo develops, the cartilage hardens to form bone. Later in development, the bone structure breaks loose from the jaw and migrates to the inner ear area. The structure is known as the middle ear, and is made up of the [[stapes]], [[incus]], [[malleus]], and [[tympanic membrane]]. These correspond to the [[columella (auditory system)|columella]], [[Quadrate bone|quadrate]], [[articular]], and [[angular bone|angular]] structures in the amphibian, bird or reptile jaw.<ref>{{cite journal |last1=Meng |first1=Jin |title=The Journey From Jaw to Ear |journal=Biologist |volume=50 |issue=4 |year=2003 |pages=154–158 |oclc=108462086 }}</ref>

=== Evolution ===
{{Main|Evolution of mammalian auditory ossicles}}

== Function ==
{{Unreferenced section|date=December 2024}}
As sound waves vibrate the tympanic membrane (eardrum), it in turn moves the nearest ossicle, the malleus, to which it is attached. The malleus then transmits the vibrations, via the incus, to the stapes, and so ultimately to the membrane of the fenestra ovalis (oval window), the opening to the vestibule of the inner ear.

Sound traveling through the air is mostly reflected when it comes into contact with a liquid medium; only about 1/30 of the sound energy moving through the air would be transferred into the liquid.<ref>Hill, R.W., Wyse, G.A. & Anderson, M. (2008). ''Animal Physiology, 2nd ed..''</ref> This is observed from the abrupt cessation of sound that occurs when the head is submerged underwater. This is because the relative incompressibility of a liquid presents resistance to the force of the sound waves traveling through the air. The ossicles give the eardrum a [[mechanical advantage]] via lever action and a reduction in the area of force distribution; the resulting vibrations are stronger but don't move as far. This allows more efficient coupling than if the sound waves were transmitted directly from the outer ear to the oval window. This reduction in the area of force application allows a large enough increase in [[pressure]] to transfer most of the sound energy into the liquid. The increased pressure will compress the fluid found in the cochlea and transmit the stimulus. Thus, the lever action of the ossicles changes the vibrations so as to improve the transfer and reception of sound, and is a form of [[impedance matching]].

However, the extent of the movements of the ossicles is controlled (and constricted) by two muscles attached to them (the ''[[tensor tympani]]'' and the ''[[stapedius]]''). It is believed that these muscles can contract to dampen the vibration of the ossicles, in order to protect the inner ear from excessively loud noise (theory 1) and that they give better frequency resolution at higher frequencies by reducing the transmission of low frequencies (theory 2) (see [[acoustic reflex]]). These muscles are more highly developed in [[bat]]s and serve to block outgoing cries of the bats during [[Animal echolocation|echolocation]] (SONAR).

== Clinical relevance ==
Occasionally the joints between the ossicles become rigid. One condition, [[otosclerosis]], results in the fusing of the stapes to the oval window. This reduces [[hearing]] and may be treated surgically using a passive [[middle ear implant]].{{explain|date=November 2017}}

== History ==
There is some doubt as to the discoverers of the auditory ossicles and several anatomists from the early 16th century have the discovery attributed to them with the two earliest being [[Alessandro Achillini]] and [[Jacopo Berengario da Carpi]].<ref>{{cite journal |pmid=14480894|year=1961|last1=O'Malley|first1=C. D.|title=The discovery of the auditory ossicles|journal=Bulletin of the History of Medicine|volume=35|pages=419–41|last2=Clarke|first2=E}}</ref> Several sources, including [[Bartolomeo Eustachi|Eustachi]] and [[Giulio Cesare Casseri|Casseri]],<ref>Alidosi, GNP. ''I dottori Bolognesi di teologia, filosofia, medicina e d'arti liberali dall'anno 1000 per tutto marzo del 1623'', Tebaldini, N., Bologna, 1623. http://gallica.bnf.fr/ark:/12148/bpt6k51029z/f35.image#</ref> attribute the discovery of the malleus and incus to the anatomist and philosopher [[Alessandro Achillini|Achillini]].<ref>Lind, L. R. ''Studies in pre-Vesalian anatomy. Biography, translations, documents'', American Philosophical Society, Philadelphia, 1975. p.40</ref> The first written description of the malleus and incus was by [[Berengario da Carpi]] in his ''Commentaria super anatomia Mundini'' (1521),<ref>Jacopo Berengario da Carpi,''Commentaria super anatomia Mundini'', Bologna, 1521. https://archive.org/details/ita-bnc-mag-00001056-001</ref> although he only briefly described two bones and noted their theoretical association with the transmission of sound.<ref name="auto">O'Malley, C.D. ''Andreas Vesalius of Brussels, 1514–1564.'' Berkeley: University of California Press, 1964. p. 120</ref> [[Niccolo Massa]]'s ''Liber introductorius anatomiae''<ref>Niccolo Massa, ''Liber introductorius anatomiae'', Venice, 1536. p.166. https://www.digitale-sammlungen.de/en/view/bsb10151904?page=1</ref> described the same bones in slightly more detail and likened them both to little hammers.<ref name="auto" /> A much more detailed description of the first two ossicles followed in [[Andreas Vesalius]]' ''[[De humani corporis fabrica]]''<ref>Andreas Vesalius, ''De humani corporis fabrica''. Johannes Oporinus, Basle, 1543.</ref> in which he devoted a chapter to them. Vesalius was the first to compare the second element of the ossicles to an anvil although he offered the molar as an alternative comparison for its shape.<ref>O'Malley, C.D. ''Andreas Vesalius of Brussels, 1514–1564.'' Berkeley: University of California Press, 1964. p. 121</ref> The first published description of the stapes came in [[Pedro Jimeno]]'s ''Dialogus de re medica'' (1549)<ref>Pedro Jimeno, ''Dialogus de re medica'', Johannes Mey, Valencia, 1549. https://archive.org/details/dialogusderemed00jimegoog</ref> although it had been previously described in public lectures by [[Giovanni Filippo Ingrassia]] at the [[University of Naples]] as early as 1546.<ref>{{cite journal|doi=10.1097/mao.0b013e31827d8abc|pmid=23370557|title=Disputes Surrounding the Discovery of the Stapes in the Mid 16th Century|journal=Otology & Neurotology|volume=34|issue=3|pages=588–592|year=2013|last1=Mudry|first1=Albert|s2cid=30466939}}</ref>

The term ''ossicle'' derives from {{lang|la|ossiculum}}, a [[diminutive]] of "bone" ({{langx|la|os}}; [[genitive]] {{lang|la|ossis}}).<ref>{{cite web|url=http://www.etymonline.com/index.php?term=ossicle|title=Online Etymology Dictionary|work=etymonline.com}}</ref> The malleus gets its name from Latin ''malleus'', meaning "hammer",<ref>{{cite web|url=http://www.etymonline.com/index.php?term=malleus|title=Online Etymology Dictionary|work=etymonline.com}}</ref> the incus gets its name from Latin ''incus'' meaning "anvil" from incudere meaning "to forge with a hammer",<ref>{{cite web|url=http://www.etymonline.com/index.php?term=incus|title=Online Etymology Dictionary|work=etymonline.com}}</ref> and the stapes gets its name from Modern Latin "stirrup", probably an alteration of Late Latin ''stapia'' related to stare "to stand" and pedem, an accusative of pes "foot", so called because the bone is shaped like a stirrup – this was an invented Modern Latin word for "stirrup", for which there was no classical Latin word, as the ancients did not use stirrups.<ref>{{cite web|url=http://www.etymonline.com/index.php?term=stapes|title=Online Etymology Dictionary|work=etymonline.com}}</ref>

== See also ==
* [[Evolution of mammalian auditory ossicles]]
{{Anatomy-terms}}
* {{annotated link|Incudomalleolar joint}}
* {{annotated link|Incudostapedial joint}}
* {{annotated link|Otolith}}

== References ==
{{reflist}}

== External links ==
{{Commons category|Ossicles}}
* [http://audilab.bmed.mcgill.ca/~daren/3Dear/mid1.html The middle ear and the ossicles]

{{Auditory system}}
{{HumanBones}}

{{Authority control}}

[[Category:Ossicles| ]]
[[Category:Auditory system]]
[[Category:Bones of the head and neck]]
[[Category:Otorhinolaryngology]]
[[Category:Otology]]
[[Category:Human head and neck]]
[[Category:Ear]]
[[Category:Middle ear]]