| Stapes | |
|---|---|
 Frontal view ofstapes (A), and view from below (B). | |
| Details | |
| Pronunciation | /ˈsteɪpiːz/ |
| Precursor | Secondbranchial arch |
| Part of | Middle ear |
| System | Auditory system |
| Articulations | Incudostapedial joint |
| Identifiers | |
| Latin | 'stapes' |
| MeSH | D013199 |
| TA98 | A15.3.02.033 |
| TA2 | 895 |
| FMA | 52751 |
| Anatomical terms of bone | |
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| This article is one of a series documenting the anatomy of the |
| Human ear |
|---|
Thestapes orstirrup is abone in themiddle ear of humans and other tetrapods which is involved in the conduction of sound vibrations to theinner ear. This bone is connected to theoval window by itsannular ligament, which allows the footplate (or base) to transmit sound energy through theoval window into the inner ear. Thestapes is the smallest and lightest bone in thehuman body, and is so-called because of its resemblance to astirrup (Latin:Stapes).
Thestapes is the third bone of the threeossicles in themiddle ear and the smallest in the human body. It measures roughly2 to 3 mm, greater along the head-base span.[1] It rests on theoval window, to which it is connected by anannular ligament and articulates with theincus, or anvil through theincudostapedial joint.[2] They are connected by anterior and posterior limbs (Latin:crura).[3]: 862
Thestapes develops from the secondpharyngeal arch during the sixth to eighth week ofembryological life. The central cavity of thestapes, theobturator foramen, is due to the presence embryologically of thestapedial artery, which usually regresses in humans during normal development.[2][4]
Thestapes is one of three ossicles in mammals. In non-mammaliantetrapods, the bonehomologous to thestapes is usually called thecolumella; however, inreptiles, either term may be used. In fish, the homologous bone is called thehyomandibular, and is part of thegill arch supporting either thespiracle or the jaw, depending on the species. The equivalent term inamphibians is thepars media plectra.[2][5]: 481–482
Thestapes appears to be relatively constant in size in different ethnic groups.[6] In 0.01–0.02% of people, the stapedial artery does not regress, and persists in the central foramen.[7] In this case, a pulsatile sound may be heard in the affected ear, or there may be no symptoms at all.[8] Rarely, thestapes may be completely absent.[9][10]: 262
Situated between the incus and the inner ear, thestapes transmits sound vibrations from the incus to the oval window, a membrane-covered opening to the inner ear. Thestapes is also stabilized by thestapedius muscle, which is innervated by thefacial nerve.[3]: 861–863
Otosclerosis is a congenital or spontaneous-onset disease characterized by abnormalbone remodeling in the inner ear. Often this causes thestapes to adhere to the oval window, which impedes its ability to conduct sound, and is a cause ofconductive hearing loss. Clinical otosclerosis is found in about 1% of people, although it is more common in forms that do not cause noticeable hearing loss. Otosclerosis is more likely in young age groups, and females.[11] Two common treatments arestapedectomy, the surgical removal of thestapes and replacement with an artificial prosthesis, andstapedotomy, the creation of a small hole in the base of thestapes followed by the insertion of an artificial prosthesis into that hole.[12]: 661 Surgery may be complicated by apersistent stapedial artery,fibrosis-related damage to the base of the bone, or obliterative otosclerosis, resulting in obliteration of the base.[7][10]: 254–262
Thestapes is commonly described as having been discovered by the professorGiovanni Filippo Ingrassia in 1546 at theUniversity of Naples,[13] although this remains the nature of some controversy, as Ingrassia's description was published posthumously in his 1603 anatomical commentaryIn Galeni librum de ossibus doctissima et expectatissima commentaria. Spanish anatomistPedro Jimeno is first to have been credited with a published description, inDialogus de re medica (1549).[14] The bone is so-named because of its resemblance to a stirrup (Latin:stapes), an example of alate Latin word, probably created inmediaeval times from "to stand" (Latin:stapia), as stirrups did not exist in the early Latin-speaking world.[15]
