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The ''stapes'' or stirrup is a
bone A bone is a rigid tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North America * ''Triphosa dubit ...

bone
in the
middle ear The middle ear is the portion of the ear The ear is the organ of hearing and, in mammals, balance. In mammals, the ear is usually described as having three parts—the outer ear The outer ear, external ear, or auris externa is th ...

middle ear
of humans and other animals which is involved in the conduction of sound vibrations to the
inner ear Inner Ear (established in 2007 in Bodø, Norway) is a Norwegian record label initiated and led by the brothers and jazz musicians Tore Johansen and Roger Johansen (musician), Roger Johansen. They opened Inner Ear to release their music when their ...

inner ear
. This bone is connected to the oval window by its annular ligament, which allows the footplate to transmit sound energy through the
oval window The oval window (or ''fenestra vestibuli'' or ''fenestra ovalis'') is a membrane-covered opening from the middle ear to the cochlea The cochlea is the part of the inner ear involved in hearing. It is a spiral-shaped cavity in the bony labyrinth, ...
into the inner ear. The ''stapes'' is the smallest and lightest bone in the
human body The human body is the structure of a Human, human being. It is composed of many different types of Cell (biology), cells that together create Tissue (biology), tissues and subsequently organ systems. They ensure homeostasis and the life, viabi ...

human body
, and is so-called because of its resemblance to a
stirrup A stirrup is a light frame or ring that holds the foot of a rider, attached to the saddle The saddle is a supportive structure for a rider of an animal, fastened to an animal's back by a girth Girth may refer to: ;Mathematics * Girth ( ...

stirrup
( la, Stapes).


Structure

The ''stapes'' is the third bone of the three
ossicles The ossicles (also called auditory ossicles) are three bone A bone is a rigid tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a spe ...
in the
middle ear The middle ear is the portion of the ear The ear is the organ of hearing and, in mammals, balance. In mammals, the ear is usually described as having three parts—the outer ear The outer ear, external ear, or auris externa is th ...

middle ear
and the smallest in the human body. It measures roughly , greater along the head-base span. It rests on the
oval window The oval window (or ''fenestra vestibuli'' or ''fenestra ovalis'') is a membrane-covered opening from the middle ear to the cochlea The cochlea is the part of the inner ear involved in hearing. It is a spiral-shaped cavity in the bony labyrinth, ...
, to which it is connected by an annular ligament and articulates with the ''
incus The ''incus'' or anvil is a bone in the middle ear. The anvil-shaped small bone is one of three ossicles in the middle ear. The ''incus'' receives vibrations from the ''malleus'', to which it is connected laterally, and transmits these to the ''s ...
'', or anvil through the
incudostapedial joint Incudostapedial joint is a small, synovial ball-and-socket joint The ball and socket joint (or spheroid joint) is a type of synovial joint A synovial joint, also known as diarthrosis, joins bones or cartilage with a fibrous joint capsule that ...
. They are connected by anterior and posterior limbs ( la, crura).


Development

The ''stapes'' develops from the second
pharyngeal arch The pharyngeal arches, also known as visceral arches'','' are structures seen in the Animal embryonic development, embryonic development of vertebrates that are recognisable precursors for many structures. In fish, the arches are known as the br ...
during the sixth to eighth week of . The central cavity of the ''stapes'', the ''obturator foramen'', is due to the presence embryologically of the
stapedial artery In human anatomy, the stapedial branch of posterior auricular artery The posterior auricular artery is a small artery An artery (plural arteries) () is a blood vessel that takes blood away from the heart to one or more parts of the body (tiss ...
, which usually regresses in humans during normal development.


Animals

The ''stapes'' is one of three ossicles in mammals. In non-mammalian four-legged animals, the bone homologous to the ''stapes'' is usually called the
columella Lucius Junius Moderatus Columella (; Arabic: Yunius, 4 – c. 70 AD) was a prominent writer on agriculture in the Roman empire. His ''De re rustica'' in twelve volumes has been completely preserved and forms an important source on Roman agri ...
; however, in
reptile Reptiles, as most commonly defined, are the animals in the class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or ...

reptile
s, either term may be used. In fish, the homologous bone is called the
hyomandibula The hyomandibula, commonly referred to as hyomandibular
one 1 (one, also called unit, and unity) is a number A number is a mathematical object used to counting, count, measurement, measure, and nominal number, label. The original examples are the natural numbers 1, 2, 3, 4, and so forth. Numbers can ...

one
( la, os hyomandibulare, from el, hyoeides, "upsilon-shaped" (υ), and Latin: mandible, mandibula, "jawbone") is a set of bones that is found in the hyoid region in most fishes. It us ...
r, and is part of the
gill arch Branchial arches, or gill arches, are a series of bony "loops" present in fish, which support the gills. As gills are the primitive condition of vertebrates, all vertebrate embryos develop pharyngeal arch The pharyngeal arches, also known as ...
supporting either the spiracle or the jaw, depending on the species. The equivalent term in
amphibian Amphibians are ectothermic, tetrapod vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial animal, ter ...
s is the '.


Variation

The ''stapes'' appears to be relatively constant in size in different ethnic groups. In 0.01–0.02% of people, the stapedial artery does not regress, and persists in the central foramen. In this case, a pulsatile sound may be heard in the affected ear, or there may be no symptoms at all. Rarely, the stapes may be completely absent.


Function

Situated between the incus and the inner ear, the stapes transmits sound vibrations from the incus to the oval window, a membrane-covered opening to the inner ear. The stapes is also stabilized by the
stapedius The stapedius is the smallest skeletal muscle in the human body. At just over one millimeter in length, its purpose is to stabilize the smallest bone in the body, the stapes. Structure The stapedius emerges from a pinpoint foramen in the apex of th ...
muscle, which is innervated by the
facial nerve The facial nerve (the labyrinthine segment) is the seventh Cranial nerves, cranial nerve, or simply CN VII. It emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of taste sensation ...

facial nerve
.


Clinical relevance

Otosclerosis Otosclerosis is a condition of the middle ear The middle ear is the portion of the ear The ear is the organ of hearing and, in mammals, balance. In mammals, the ear is usually described as having three parts—the outer ear T ...
is a congenital or spontaneous-onset disease characterized by abnormal
bone remodeling Bone remodeling (or bone metabolism) is a lifelong process where mature bone tissue A bone is a rigid tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Trip ...
in the inner ear. Often this causes the stapes to adhere to the oval window, which impedes its ability to conduct sound, and is a cause of
conductive hearing loss Conductive hearing loss (CHL) occurs when there is a problem transferring sound wave In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is th ...
. 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. Two common treatments are stapedectomy, the surgical removal of the stapes and replacement with an artificial prosthesis, and stapedotomy, the creation of a small hole in the base of the stapes followed by the insertion of an artificial prosthesis into that hole. Surgery may be complicated by a persistent stapedial artery,
fibrosis Fibrosis, also known as fibrotic scarring, is a pathological wound healing in which connective tissue replaces normal parenchymal tissue to the extent that it goes unchecked, leading to considerable tissue remodelling and the formation of permane ...
-related damage to the base of the bone, or obliterative otosclerosis, resulting in obliteration of the base.


History

The stapes is commonly described as having been discovered by the professor in 1546 at the
University of Naples The University of Naples Federico II ( it, Università degli Studi di Napoli Federico II) is a public university #REDIRECT Public university #REDIRECT Public university #REDIRECT Public university#REDIRECT Public university A public university ...
, although this remains the nature of some controversy, as Ingrassia's description was published posthumously in his 1603 anatomical commentary '. Spanish anatomist Pedro Jimeno is first to have been credited with a published description, in (1549). The bone is so-named because of its resemblance to a stirrup ( la, stapes), an example of a
late Latin Late Latin ( la, Latinitas serior) is the scholarly name for the written Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, kn ...
word, probably created in
mediaeval In the history of Europe, the Middle Ages or medieval period lasted approximately from the 5th to the late 15th centuries, similarly to the Post-classical, Post-classical period of global history. It began with the fall of the Western Rom ...
times from "to stand" ( la, stapia), as stirrups did not exist in the early Latin-speaking world.


References


External links

* {{Good article Auditory system
Skeletal system {{Commons cat, Skeletal system A skeleton (endoskeleton) is made up of bones. ''See also:'' :Bone products Musculoskeletal system ...
Skull Ossicles