WordNet

a small bone; especially one in the middle ear (同)bonelet, ossiculum
ossicles of the middle ear that transmit acoustic vibrations from the eardrum to the inner ear

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/04/10 17:10:34」(JST)

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Not to be confused with Ossicone.

The ossicles (also called auditory ossicles) are the three smallest bones in the human body, the malleus, the incus and the stapes. They are contained within the middle ear space and serve to transmit sounds from the air to the fluid-filled labyrinth (cochlea). The absence of the auditory ossicles would constitute a moderate-to-severe hearing loss. The term "ossicles" literally means "tiny bones" and commonly refers to the auditory ossicles, though the term may refer to any small bone throughout the body.

Etymology

Ossicle dates to c. 1570, from Latin Ossiculum, a diminutive of Latin Os "bone" (Genitive: Ossis).^[1] The malleus gets its name from Latin malleus, meaning "hammer",^[2] the Incus gets its name from Latin Incus meaning "anvil" from incudere meaning "to forge with a hammer",^[3] 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.^[4]

Anatomy

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, the anvil, and the stirrup.

The malleus (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 (anvil) is connected to both the other bones.
The stapes (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 inner ear. It is the smallest bone in the body.^[5]

Function

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, the opening to the vestibule of the inner ear.

The ossicles give the eardrum mechanical advantage via lever action and a reduction in the area of force distribution; the resulting vibrations would be much smaller if the sound waves were transmitted directly from the outer ear to the oval window. However, the extent of the movements of the ossicles is controlled (and constricted) by certain 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 bats and serve to block outgoing cries of the bats during echolocation (SONAR).

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.

The quality of sound is improved by impedance matching.

Development

Studies have shown that ear bones in mammal embryos are attached to the dentary, which is part of the 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 incus, stapes, malleus, and tympanic membrane. These correspond to the quadrate, prearticular, articular, and angular structures in the reptile jaw. For this reason, researchers believe that mammals and reptiles share a common ancestry.^[6]

References

^ http://www.etymonline.com/index.php?term=ossicle
^ http://www.etymonline.com/index.php?term=malleus
^ http://www.etymonline.com/index.php?term=incus
^ http://www.etymonline.com/index.php?term=stapes
^ http://kidshealth.org/kid/htbw/bones.html
^ Meng, Jin. "The Journey From Jaw to Ear." Biologist. vol. 50. (2003) p. 154-158.

External links

The middle ear and the ossicles

UpToDate Contents

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English Journal

Three-dimensional vibration of the malleus and incus in the living gerbil.

Decraemer WF1, de La Rochefoucauld O, Funnell WR, Olson ES.
Journal of the Association for Research in Otolaryngology : JARO.J Assoc Res Otolaryngol.2014 Aug;15(4):483-510. doi: 10.1007/s10162-014-0452-1. Epub 2014 Apr 2.
In previous studies, 3D motion of the middle-ear ossicles in cat and human was explored, but models for hearing research have shifted in the last few decades to smaller mammals, and gerbil, in particular, has become a popular hearing model. In the present study, we have measured with an optical inte
PMID 24691793

Ossiculoplasty: a prospective study of 80 cases.

Chavan SS, Jain PV, Vedi JN, Rai DK, Kadri H.
Iranian journal of otorhinolaryngology.Iran J Otorhinolaryngol.2014 Jul;26(76):143-50.
INTRODUCTION: The use of ossicular graft material in ossicular chain reconstruction has significantly improved hearing results hearing after tympanoplasty and tympanomastoid surgery for chronic otitis media. Today, otologists have a wide array of tools from which to choose, but may find it difficult
PMID 25009804

MR Imaging-based Diagnosis and Classification of Meniscal Tears.

Nguyen JC1, De Smet AA, Graf BK, Rosas HG.
Radiographics : a review publication of the Radiological Society of North America, Inc.Radiographics.2014 Jul-Aug;34(4):981-99. doi: 10.1148/rg.344125202.
Magnetic resonance (MR) imaging is currently the modality of choice for detecting meniscal injuries and planning subsequent treatment. A thorough understanding of the imaging protocols, normal meniscal anatomy, surrounding anatomic structures, and anatomic variants and pitfalls is critical to ensure
PMID 25019436

Japanese Journal

二次性真珠腫の進展方向について:―緊張部型真珠腫との比較―

金沢弘美,長谷川雅世,原真理子,松澤真吾,新鍋晶浩,吉田尚弘,飯野ゆき子
頭頸部外科 23(1), 49-54, 2013
二次性真珠腫は穿孔縁から上皮が回りこんで真珠腫を形成するといわれており，真珠腫全体における割合は高くはない。今回われわれは，同じ緊張部に病変を有する緊張部型真珠腫と各検査所見や実際の術中所見を比較し，その特徴について検討した。対象は当院で2008～2011年の4年間に手術加療を行った二次性真珠腫22耳，緊張部型真珠腫32耳である。検討の結果，両者の間に年齢差はなく，進展度や耳小骨骨破壊は二次性真珠 …
NAID 130003373807

Redescription of the ossicles of the deep-sea cucumber Bathyplotes tizardi (Theel, 1882) from the East China Sea, Nagasaki, Japan

Soliman Taha,Solis-Marin Francisco A.,Yamazaki Yuji
Biogeography 14, 25-29, 2012-09
NAID 40019471688

当科での先天性耳小骨奇形の術後成績について

桂弘和,武藤俊彦,三代康雄,足達治,阪上雅史
Otology Japan 21(5), 795-799, 2011-12-26
最近10年間に兵庫医科大学耳鼻咽喉科で手術を行った耳小骨奇形症例の38症例41耳について検討した。男性13例、女性25例で手術時の年齢は4歳から48歳 (平均20歳) であった。船坂の分類では1群が最も多く20例で、2群が10例、3群が6例であった。術前ティンパノメトリは離断症例でA型が最も多く、固着症例ではC型が最も多くみられた。耳小骨筋反射は反対側刺激で離断症例のうち9例 (82%)で反応がみ …
NAID 10030285270

Related Pictures

★リンクテーブル★

リンク元	「小骨」
拡張検索	「ear ossicle」

「小骨」

Ossicles
	Ossicles
	Chain of ossicles and their ligaments, seen from the front in a vertical, transverse section of the tympanum.
Latin	ossicula auditus; ossicula auditoria
Gray's	subject #231 1044
MeSH	Ear+Ossicles
Dorlands/Elsevier	Ossicles