View source for Ear

{{short description|Organ of hearing and balance}}
{{Other uses}}
{{pp-vandalism|small=yes}}
{{Use dmy dates|date=March 2020}}
{{good article}}
{{Infobox anatomy
| Name        = Ear
| Latin       = auris
| Greek       =
| Image       = Human right ear (cropped).jpg
| Caption     = The outer portion of the human ear<br />[[File:En-uk-ear.ogg|thumb|{{center|"Ear" pronounced (''[[Received Pronunciation]]'')}}]]
| Width       = 250
| Image2      =
| Caption2    =
| Precursor   =
| System      = [[Auditory system]]
| Artery      =
| Vein        =
| Nerve       =
| Lymph       =
}}
{{Ear series}}
[[File:Journey of Sound to the Brain.ogg|thumb|How sounds make their way from the source to the human brain|350x350px]]

In [[vertebrate]]s, an '''ear''' is the [[organ (anatomy)|organ]] that enables [[hearing]] and (in [[mammal]]s) [[Sense of balance|body balance]] using the [[vestibular system]]. In humans, the ear is described as having three parts:  the [[outer ear]], the [[middle ear]] and the [[inner ear]]. The outer ear consists of the [[Auricle (anatomy)|auricle]] and the [[ear canal]]. Since the outer ear is the only visible portion of the ear, the word "ear" often refers to the external part (auricle) alone.<ref name="Oxford">{{cite web|title=Ear|url=http://www.oxforddictionaries.com/definition/english/ear|archive-url=https://web.archive.org/web/20120718030833/http://oxforddictionaries.com/definition/english/ear|url-status=dead|archive-date=18 July 2012|website=Oxford Dictionary|access-date=25 February 2016}}</ref> The middle ear includes the [[tympanic cavity]] and the three [[ossicle]]s. The inner ear sits in the [[bony labyrinth]], and contains structures which are key to several senses: the [[semicircular canal]]s, which enable balance and eye tracking when moving; the [[utricle (ear)|utricle]] and [[saccule]], which enable balance when stationary; and the [[cochlea]], which enables hearing. The ear canal is cleaned via [[earwax]], which naturally migrates to the auricle. 

The ear develops from the first [[pharyngeal pouch (embryology)|pharyngeal pouch]] and six small swellings that develop in the early [[embryo]] called [[otic placode]]s, which are derived from the [[ectoderm]].

The ear may be affected by disease, including infection and traumatic damage. Diseases of the ear may lead to [[hearing loss]], [[tinnitus]] and [[balance disorders]] such as [[vertigo]], although many of these conditions may also be affected by damage to the brain or neural pathways leading from the ear.

The human ear has been adorned by [[earring]]s and other jewelry in numerous cultures for thousands of years, and has been subjected to surgical and cosmetic alterations.

==Structure==
The human ear consists of three parts—the [[outer ear]], [[middle ear]] and [[inner ear]].<ref name="GRAYS40TH_36">{{cite book|last1=Standring|first1=Susan|editor1-last=Borley|editor1-first=Neil R.|title=Gray's Anatomy: The Anatomical Basis of Clinical Practice|date=2008|publisher=[[Churchill Livingstone]]/[[Elsevier]]|location=[[Edinburgh]]|isbn=978-0-443-06684-9|edition=40|pages=Chapter 36. "External and middle ear", 615–631|url=https://books.google.com/books?id=kvhkPQAACAAJ}} [https://archive.org/stream/GraysAnatomy40thEd_201403/Gray's%20Anatomy%20-%2040th%20Ed_djvu.txt Alt URL]</ref> The [[ear canal]] of the outer ear is separated from the air-filled [[tympanic cavity]] of the middle ear by the [[eardrum]]. The middle ear contains the three small bones—the [[ossicles]]—involved in the transmission of sound, and is connected to the [[throat]] at the [[nasopharynx]], via the [[pharyngeal opening of auditory tube|pharyngeal opening]] of the [[Eustachian tube]]. The inner ear contains the [[otolith]] organs—the [[utricle (ear)|utricle]] and [[saccule]]—and the [[semicircular canal]]s belonging to the [[vestibular system]], as well as the [[cochlea]] of the [[auditory system]].<ref name="GRAYS40TH_36" />

===Outer ear===
{{main|Outer ear}}
The outer ear is the external portion of the ear and includes the fleshy visible [[Auricle (anatomy)|auricle]], the ear canal, and the outer layer of the eardrum (also called the tympanic membrane).<ref name="GRAYS40TH_36" /><ref name=GRAYS2005>{{cite book|last=Drake|first=Richard L.|title=Gray's anatomy for students|year=2005|publisher=Elsevier/Churchill Livingstone|location=Philadelphia|isbn=978-0-8089-2306-0|pages=855–856|author2=Vogl, Wayne |author3=Tibbitts, Adam W.M. Mitchell  |author4=illustrations by Richard |author5= Richardson, Paul }}</ref>

The auricle consists of the curving outer rim called the [[helix (ear)|helix]], the inner curved rim called the [[antihelix]], and opens into the ear canal. The [[tragus (ear)|tragus]] protrudes and partially obscures the ear canal, as does the facing [[antitragus]]. The hollow region in front of the ear canal is called the concha. The ear canal stretches for about 1{{Nbsp}}inch (2.5{{Nbsp}}cm). The first part of the canal is surrounded by [[cartilage]], while the second part near the eardrum is surrounded by [[bone]]. This bony part is known as the [[auditory bulla]] and is formed by the [[tympanic part of the temporal bone]]. The ear canal ends at the external surface of the eardrum, while the surrounding skin contains [[ceruminous gland|ceruminous]] and [[sebaceous gland]]s that produce protective [[earwax]].<ref name="GRAYS2005" /> Earwax naturally migrates outward through ear canal, constituting a self-cleaning system.<ref name="Shmerling 2017 i652">{{cite web |last=Shmerling |first=Robert H. |date=2017-05-17 |title=3 reasons to leave earwax alone |url=https://www.health.harvard.edu/blog/3-reasons-to-leave-earwax-alone-2017051711718 |access-date=2023-07-11 |website=Harvard Health}}</ref><ref name="Keck Medicine of USC 2022 s129">{{cite web |date=2022-09-29 |title=Why Do I Have So Much Earwax? |url=https://internalmedicine.usc.edu/blog/why-do-i-have-so-much-earwax/ |access-date=2023-07-11 |website=Keck Medicine of USC}}</ref><ref name="HealthLink BC 2021 t871">{{cite web |date=2021-07-01 |title=Earwax |url=https://www.healthlinkbc.ca/health-topics/earwax |access-date=2023-07-11 |website=HealthLink BC}}</ref><ref name="MyHealth.Alberta.ca 2023 a639">{{cite web |date=2023-07-11 |title=Earwax |url=https://myhealth.alberta.ca/Health/Pages/conditions.aspx?hwid=earwx |access-date=2023-07-11 |website=MyHealth.Alberta.ca |ref={{sfnref | MyHealth.Alberta.ca | 2023}}}}</ref>

Two sets of muscles are associated with the outer ear: the [[Outer ear#Intrinsic muscles|intrinsic]] and [[Outer ear#Extrinsic muscles|extrinsic]] muscles. In some mammals, these muscles can adjust the direction of the pinna.<ref name= GRAYS2005 /> In humans, these muscles have little or no effect.<ref name=Moore>{{cite book|vauthors=Moore KL, Dalley AF, Agur AM |date=2013|title=Clinically Oriented Anatomy, 7th ed.|publisher=Lippincott Williams & Wilkins|pages=848–849|isbn=978-1-4511-8447-1}}</ref> The ear muscles are supplied by the [[facial nerve]], which also supplies sensation to the skin of the ear itself, as well as to the external ear cavity. The [[great auricular nerve]], [[auricular branch of vagus nerve|auricular nerve]], [[auriculotemporal nerve]], and [[lesser occipital nerve|lesser]] and [[greater occipital nerve]]s of the [[cervical plexus]] all supply sensation to parts of the outer ear and the surrounding skin.<ref name= GRAYS2005 />

The auricle consists of a single piece of [[elastic cartilage]] with a complicated relief on its inner surface and a fairly smooth configuration on its posterior surface. A [[tubercle (anatomy)|tubercle]], known as [[Darwin's tubercle]], is sometimes present, lying in the descending part of the helix and corresponding to the ear-tip of mammals. The [[earlobe]] consists of [[loose connective tissue|areola]] and [[adipose tissue]].<ref>Stenström, J. Sten: Deformities of the ear; In: Grabb, W., C., Smith, J.S. (Edited): "Plastic Surgery", Little, Brown and Company, Boston, 1979, {{ISBN|0-316-32269-5}} (C), {{ISBN|0-316-32268-7}} (P)</ref> The symmetrical arrangement of the two ears allows for the [[sound localization|localisation of sound]]. The brain accomplishes this by comparing [[interaural time difference|arrival-times]] and [[intensity (physics)|intensities]] from each ear, in circuits located in the [[superior olivary complex]] and the [[Trapezoid body|trapezoid bodies]], which are connected via pathways to both ears.<ref name="purves">{{cite book|last1=Purves|first1=D.|title=Neuroscience|date=2007|publisher=Sinauer|location=New York|isbn=978-0-87893-697-7|pages=332–336|edition=4th}}</ref>
{{Clear}}

===Middle ear===
{{main|Middle ear}}
[[File:Blausen 0330 EarAnatomy MiddleEar.png|thumb|right|350px|The middle ear]]
The middle ear lies between the outer ear and the inner ear. It consists of an air-filled cavity called the [[tympanic cavity]] and includes the three [[ossicles]] and their attaching ligaments; the [[Eustachian tube|auditory tube]]; and the [[round window|round]] and [[oval window]]s. The ossicles are three small bones that function together to receive, amplify, and transmit the sound from the eardrum to the inner ear. The ossicles are the [[malleus]] (hammer), [[incus]] (anvil), and the [[stapes]] (stirrup). The stapes is the smallest named bone in the [[human body|body]]. The middle ear also connects to the upper [[throat]] at the [[nasopharynx]] via the [[pharyngeal opening of auditory tube|pharyngeal opening]] of the Eustachian tube.<ref name=GRAYS2005 /><ref>{{cite book|last1=Mitchell|first1=Richard L. Drake, Wayne Vogl, Adam W.M.|title=Gray's anatomy for students|date=2005|publisher=Elsevier|location=Philadelphia|isbn=978-0-8089-2306-0|page=858}}</ref>

The three ossicles transmit sound from the outer ear to the inner ear. The malleus receives vibrations from sound pressure on the eardrum, where it is connected at its longest part (the manubrium or handle) by a ligament. It transmits vibrations to the incus, which in turn transmits the vibrations to the small stapes bone. The wide base of the stapes rests on the oval window. As the stapes vibrates, vibrations are transmitted through the oval window, causing movement of fluid within the [[cochlea]].<ref name="GRAYS2005" />

The round window allows for the fluid within the inner ear to move. As the stapes pushes the [[secondary tympanic membrane]], fluid in the inner ear moves and pushes the membrane of the round window out by a corresponding amount into the middle ear. The ossicles help amplify sound waves by nearly 15–20 times.<ref name="GRAYS40TH_36" />

===Inner ear===
[[File:Blausen 0329 EarAnatomy InternalEar.png|350px|thumbnail|right|The outer ear receives sound, transmitted through the [[ossicles]] of the middle ear to the [[inner ear]], where it is converted to a nervous signal in the [[cochlear nerve|cochlear]] and transmitted along the [[vestibulocochlear nerve]].]]{{main|Inner ear}}
The inner ear sits within the temporal bone in a complex cavity called the [[bony labyrinth]]. A central area known as the [[vestibule of the ear|vestibule]] contains two small fluid-filled recesses, called the [[Utricle (ear)|utricle]] and [[saccule]]. These connect to the [[semicircular canal]]s and the [[cochlea]]. There are three semicircular canals angled at right angles to each other which are responsible for dynamic balance. The cochlea is a spiral shell-shaped organ responsible for the sense of hearing. These structures together create the [[membranous labyrinth]].<ref name="GRAYS40TH_37">{{cite book|last1=Standring|first1=Susan|editor1-last=Borley|editor1-first=Neil R.|title=Gray's Anatomy: The Anatomical Basis of Clinical Practice|date=2008|publisher=[[Churchill Livingstone]]/[[Elsevier]]|location=[[Edinburgh]]|isbn=978-0-443-06684-9|edition=40|pages=Chapter 37. "Inner ear", 633–650}}</ref>

The bony labyrinth refers to the bony compartment which contains the membranous labyrinth, contained within the temporal bone. The inner ear structurally begins at the oval window, which receives vibrations from the incus of the middle ear. Vibrations are transmitted into the inner ear into a fluid called [[endolymph]], which fills the membranous labyrinth. The endolymph is situated in two vestibules, the utricle and saccule, and eventually transmits to the cochlea, a spiral-shaped structure. The cochlea consists of three fluid-filled spaces: the [[vestibular duct]], the [[cochlear duct]], and the [[tympanic duct]].<ref name="GRAYS2005" /> [[Hair cell]]s responsible for [[transduction (physiology)|transduction]]—changing mechanical changes into electrical stimuli are present in the [[organ of Corti]] in the cochlea.<ref name="GRAYS40TH_37" />

===Blood supply===
The blood supply of the ear differs according to each part of the ear.

The outer ear is supplied by a number of arteries. The [[posterior auricular artery]] provides the majority of the blood supply. The [[anterior auricular branches|anterior auricular arteries]] provide some supply to the outer rim of the ear and scalp behind it. The posterior auricular artery is a direct branch of the external carotid artery, and the anterior auricular arteries are branches from the [[superficial temporal artery]]. The [[occipital artery]] also plays a role.<ref name=GRAYS40TH_37 />

The middle ear is supplied by the mastoid branch of either the [[occipital artery|occipital]] or [[posterior auricular artery|posterior auricular arteries]] and the [[deep auricular artery]], a branch of the [[maxillary artery]]. Other arteries which are present but play a smaller role include branches of the [[middle meningeal artery]], [[ascending pharyngeal artery]], [[internal carotid artery]], and the artery of the [[pterygoid canal]].<ref name=GRAYS40TH_37 />

The inner ear is supplied by the anterior tympanic branch of the maxillary artery; the stylomastoid branch of the posterior auricular artery; the petrosal branch of middle meningeal artery; and the [[labyrinthine artery]], arising from either the [[anterior inferior cerebellar artery]] or the [[basilar artery]].<ref name="GRAYS40TH_37" />

==Functions==

===Hearing===
{{Main|Hearing}}
[[Sound wave]]s travel through the outer ear, are modulated by the middle ear, and are transmitted to the [[vestibulocochlear nerve]] in the inner ear. This nerve transmits information to the [[temporal lobe]] of the brain, where it is registered as sound.

Sound that travels through the outer ear impacts on the eardrum, and causes it to vibrate. The three ossicles bones transmit this sound to a second window (the [[oval window]]), which protects the fluid-filled inner ear. In detail, the pinna of the outer ear helps to focus a sound, which impacts on the eardrum. The malleus rests on the membrane, and receives the vibration. This vibration is transmitted along the incus and stapes to the oval window. Two small muscles, the [[tensor tympani]] and [[stapedius]], also help modulate noise. The two muscles [[Acoustic reflex|reflexively contract]] to dampen excessive vibrations. Vibration of the oval window causes vibration of the endolymph within the [[vestibule of the ear|vestibule]] and the cochlea.<ref name=HALL2005 >{{cite book|last=Hall|first2=Arthur C. |last2=Guyton|first=John E.|title=Textbook of Medical Physiology|year=2005|publisher=W.B. Saunders|location=Philadelphia|isbn=978-0-7216-0240-0|pages=651–657|edition=11th}}</ref>

The inner ear houses the apparatus necessary to [[transduction (physiology)|change the vibrations]] transmitted from the outside world via the middle ear into signals passed along the vestibulocochlear nerve to the brain. The hollow channels of the inner ear are filled with liquid, and contain a sensory [[epithelium]] that is studded with [[hair cells]]. The microscopic "hairs" of these cells are structural protein filaments that project out into the fluid. The hair cells are [[mechanoreceptor]]s that release a chemical [[neurotransmitter]] when stimulated. Sound waves moving through fluid flows against the [[Receptor (biochemistry)|receptor]] cells of the organ of Corti. The fluid pushes the filaments of individual cells; movement of the filaments causes receptor cells to become open to receive the [[potassium]]-rich endolymph. This causes the cell to depolarise, and creates an [[action potential]] that is transmitted along the [[spiral ganglion]], which sends information through the auditory portion of the vestibulocochlear nerve to the [[temporal lobe]] of the brain.<ref name=HALL2005 />

The human ear can generally hear sounds with frequencies between 20 [[Hertz|Hz]] and 20 [[kHz]] ([[Sound#Perception|the audio range]]). Sounds outside this range are considered [[infrasound]] (below 20&nbsp;Hz)<ref>Greinwald, John H. Jr MD; Hartnick, Christopher J. MD The Evaluation of Children With Sensorineural Hearing Loss. [[JAMA Otolaryngology–Head & Neck Surgery|Archives of Otolaryngology–Head & Neck Surgery]]. 128(1):84–87, January 2002</ref> or [[ultrasound]] (above 20&nbsp;kHz)<ref>{{Cite web|url=http://www.collinsdictionary.com/dictionary/english/ultrasound|title=Definition of "ultrasound" |website=Collins English Dictionary |access-date=2016-03-20}}</ref> Although hearing requires an intact and functioning auditory portion of the [[central nervous system]] as well as a working ear, human deafness (extreme insensitivity to sound) most commonly occurs because of abnormalities of the inner ear, rather than in the nerves or tracts of the central auditory system.

===Balance===
{{Main|Balance (ability)|Equilibrioception}}
Providing balance, when moving or stationary, is also a central function of the ear. The ear facilitates two types of balance: static balance, which allows a person to feel the effects of [[gravity]], and dynamic balance, which allows a person to sense acceleration.

Static balance is provided by two ventricles, the utricle and the saccule. Cells lining the walls of these ventricles contain fine filaments, and the cells are covered with a fine gelatinous layer. Each cell has 50–70 small filaments, and one large filament, the [[kinocilium]]. Within the gelatinous layer lie [[otolith]]s, tiny formations of [[calcium carbonate]]. When a person moves, these otoliths shift position. This shift alters the positions of the filaments, which opens [[ion channel]]s within the cell membranes, creating [[depolarisation]] and an [[action potential]] that is transmitted to the brain along the vestibulocochlear nerve.<ref name=HALL2005 /><ref>{{cite book|last=Hall|first2=Arthur C. |last2=Guyton|first=John E.|title=Textbook of Medical Physiology|year=2005|publisher=W.B. Saunders|location=Philadelphia|isbn=978-0-7216-0240-0|pages=692–694|edition=11th}}</ref>

Dynamic balance is provided through the three semicircular canals. These three canals are orthogonal (at right angles) to each other. At the end of each canal is a slight enlargement, known as the [[osseous ampullae|ampulla]], which contains numerous cells with filaments in a central area called the [[ampullary cupula|cupula]]. The fluid in these canals rotates according to the momentum of the head. When a person changes acceleration, the inertia of the fluid changes. This affects the pressure on the cupula, and results in the opening of ion channels. This causes depolarisation, which is passed as a signal to the brain along the vestibulocochlear nerve.<ref name=HALL2005 /> Dynamic balance also helps maintain eye tracking when moving, via the [[vestibulo-ocular reflex]].

==Development==
During [[embryogenesis]], the ear develops as three distinct structures: the inner ear, the middle ear and the outer ear.<ref name=moore2009>{{cite book |last=Moore |first=Keith L. |author-link=Keith L. Moore |year=2009 |title=Fundamentos de Anatomía con Orientación Clínica |pages=1021–1035}}</ref> Each structure originates from a different [[germ layer]]: the [[ectoderm]], [[endoderm]] and [[mesenchyme]].<ref name=sadler2012>{{cite book |last=Sadler |first=T.W. |author-link=T.W. Sadler |year=2010 |title=Embriología Médica|pages=321–327}}</ref><ref name=moore2008>{{cite book |last=Moore |first=Keith L. |year=2008 |title=Embriología Clínica |pages=477–482}}</ref>

===Inner ear===
[[File:G1. Otic placode (V07a).png|thumb|The [[otic placode]] on a developing embryo (about four weeks old)]]
[[File:Gray62.png|thumb|The ear develops in the lower neck region and moves upwards as the [[mandible]] develops (six weeks).]]

Around its second to third week, the developing embryo consists of three layers: ectoderm, [[mesoderm]], and endoderm. The first part of the ear to develop is the inner ear,<ref name=moore2008/> which begins to form from the ectoderm around the embryo's 22nd day,<ref name=sadler2012/> derived from two thickenings called [[otic placode]]s on either side of the head. Each otic placode recedes below the ectoderm, forms an [[otic pit]] and then an [[otic vesicle]].<ref name="GRAYS40th_38">{{cite book|last1=Standring|first1=Susan|editor1-last=Borley|editor1-first=Neil R.|title=Gray's Anatomy: The Anatomical Basis of Clinical Practice|date=2008|publisher=[[Churchill Livingstone]]/[[Elsevier]]|location=[[Edinburgh]]|isbn=978-0-443-06684-9|edition=40|pages=Chapter 38. "Development of the ear", 651–653}}</ref> This entire mass is eventually surrounded by mesenchyme to form the bony labyrinth.<ref name=GRAYS40th_38 /><ref name=UNSWembryology>{{cite book |title= UNSW Embryology. Hearing-Inner Ear Development |url= http://php.med.unsw.edu.au/embryology/index.php?title=Hearing_-_Inner_Ear_Development |access-date= 20 April 2013 |url-status=dead |archive-url= https://web.archive.org/web/20120930063158/http://php.med.unsw.edu.au/embryology/index.php?title=Hearing_-_Inner_Ear_Development |archive-date= 30 September 2012}}</ref>

Around the 28th day, parts of the otic vesicle begin to form the vestibulocochlear nerve.<ref name="GRAYS40th_38" /><ref name="drake2010">{{cite book |last1=Drake |first1=Richard L. |author-link=Richard L. Drake |title=GRAY Anatomía para estudiantes |last2=Wayne |first2=A. |author-link2=A. Wayne |last3=Mitchell |first3=Adam |author-link3=Adam Mitchell (scientist) |year=2010 |pages=854–871}}</ref> These form [[bipolar neuron]]s, which supply sensation to parts of the inner ear (namely the sensory parts of the semicircular canals, macular of the utricle and saccule, and organ of Corti).<ref name="GRAYS40th_38" />

Around the 33rd day, the vesicles begin to differentiate. Posteriorly, they form what will become the utricle and semicircular canals. Anteriorly, the vesicles differentiate into a rudimentary saccule, which eventually becomes the saccule and cochlea. Part of the saccule eventually gives rise and connects to the cochlear duct, which appears approximately during the sixth week and connects to the saccule through the [[ductus reuniens]].<ref name="sadler2012" />

As the cochlear duct's mesenchyme begins to differentiate, three cavities are formed: the [[scala vestibuli]], the [[scala tympani]] and the [[scala media]].<ref name="sadler2012" /><ref name="UNSWembryology" /> Both the scala vestibuli and the scala tympani contain an extracellular fluid called [[perilymph]], while the scala media contains endolymph.<ref name="UNSWembryology" /> The [[vestibular membrane]] and the [[basilar membrane]] develop to separate the cochlear duct from the vestibular duct and the tympanic duct, respectively.<ref name="sadler2012" />

;Molecular regulation
Most of the genes responsible for the [[Regulation of gene expression|regulation]] of inner ear formation and its [[morphogenesis]] are members of the [[homeobox gene]] family such as [[Pax genes|Pax]], Msx and Otx homeobox genes. The development of inner ear structures such as the [[cochlea]] is regulated by [[DLX5 (gene)|Dlx5]]/[[DLX6 (gene)|Dlx6]], [[OTX1 (gene)|Otx1]]/[[OTX2 (gene)|Otx2]] and [[PAX2|Pax2]], which in turn are controlled by the master [[SHH (gene)|gene Shh]]. Shh is secreted by the [[notochord]].<ref name=sumantra2010>{{cite journal |last1=Chatterjee |first1=Sumantra |author-link=Sumantra Chatterjee |last2=Kraus |first2=Petra |author-link2=Petra Krauss |last3=Luftkin |first3=Thomas |author-link3=Thomas Luftkin |year=2010 |title= A symphony of inner ear developmental control genes |journal=BMC Genetics |volume=11 |article-number=68 |doi=10.1186/1471-2156-11-68 |pmid=20637105 |pmc=2915946 |doi-access=free }}</ref>

===Middle ear===
The middle ear and its components develop from the first and second [[pharyngeal arch]]es.<ref name=GRAYS40th_38 /> The tympanic cavity and auditory tube develop from the first part of the [[pharyngeal pouch (embryology)|pharyngeal pouch]] between the first two arches in an area which will also go on to develop the [[pharynx]]. This develops as a structure called the [[tubotympanic recess]].<ref name=GRAYS40th_38 /> The ossicles (malleus, incus and stapes) normally appear during the first half of fetal development. The first two (malleus and incus) derive from the first pharyngeal arch and the stapes derives from the second.<ref name=sadler2012/> All three ossicles develop from the [[neural crest]].<ref name=GRAYS40th_38 /> Eventually, cells from the tissue surrounding the ossicles will experience [[apoptosis]] and a new layer of endodermal epithelial will constitute the formation of the tympanic cavity wall.<ref name=sadler2012/><ref name=moore2008/>

===Outer ear===

Unlike structures of the inner and middle ear, which develop from pharyngeal pouches, the ear canal originates from the dorsal portion of the first [[pharyngeal cleft]].<ref name=sadler2012/><ref name=GRAYS40th_38 /> It is fully expanded by the end of the 18th week of development.<ref name=UNSWembryology/> The eardrum is made up of three layers (ectoderm, endoderm and connective tissue). The auricle originates as a fusion of six hillocks. The first three hillocks are derived from the lower part of the first pharyngeal arch and form the tragus, crus of the helix, and helix, respectively. The final three hillocks are derived from the upper part of the second pharyngeal arch and form the antihelix, antitragus, and earlobe.<ref name=sadler2012/><ref name=GRAYS40th_38 /><ref name=UNSWembryology/> The outer ears develop in the lower [[neck]]. As the [[mandible]] forms, they move towards their final position level with the eyes.<ref name=moore2009/><ref name=drake2010/>

===Growth===
The ears of newborn humans are proportionally very large, even more so than the head's largeness as compared to the body. Ears grow quickly until about the age of nine, then continue to grow steadily in circumference (about 0.5 millimeters a year) throughout life, with the increase in length more extreme in males.<ref>{{Cite journal |last1=Niemitz |first1=Carsten |last2=Nibbrig |first2=Maike |last3=Zacher |first3=Vanessa |date=December 2007 |title=Human ears grow throughout the entire lifetime according to complicated and sexually dimorphic patterns--conclusions from a cross-sectional analysis |journal=Anthropologischer Anzeiger; Bericht Uber die Biologisch-Anthropologische Literatur |volume=65 |issue=4 |pages=391–413 |doi=10.1127/anthranz/65/2007/391 |issn=0003-5548 |pmid=18196763}}</ref><ref>{{Cite journal |last1=Tan |first1=R |last2=Osman |first2=V |last3=Tan |first3=G |date=1997-10-01 |title=Ear size as a predictor of chronological age |url=https://www.sciencedirect.com/science/article/pii/S0167494397000101 |journal=Archives of Gerontology and Geriatrics |volume=25 |issue=2 |pages=187–191 |doi=10.1016/S0167-4943(97)00010-1 |pmid=18653105 |issn=0167-4943|url-access=subscription }}</ref>

=== Uniqueness ===
Ears are individually almost unique, with the odds of two people having matching ears being very low.<ref>{{Cite web |date=2023-07-14 |title=Ears as effective as DNA in identifying people - new study |url=https://www.rnz.co.nz/national/programmes/checkpoint/audio/2018898315/ears-as-effective-as-dna-in-identifying-people-new-study |access-date=2024-06-04 |website=[[RNZ]] |language=en-nz}}</ref> Additionally, the ear's proportions are normally retained for life, and have thus been employed for [[forensic identification]] since the 1950s.<ref>{{Cite web |last=Tangalakis-Lippert |first=Katherine |date=2023-03-19 |title=Is Putin using a body double? Listen here: Skeptics say spotting a decoy is all in the ears. |url=https://www.businessinsider.com/vladimir-putin-ukraine-trip-body-double-conspiracy-theories-ears-2023-3 |access-date=2023-03-22 |website=[[Business Insider]] |language=en-US}}</ref>

==Clinical significance==

===Hearing loss===
{{Main|Hearing loss}}

Hearing loss may be either partial or total. This may be a result of injury or damage, [[congenital disease]], or [[physiological]] causes. When hearing loss is a result of injury or damage to the outer ear or middle ear, it is known as [[conductive hearing loss]]. When deafness is a result of injury or damage to the inner ear, vestibulochoclear nerve, or brain, it is known as [[sensorineural hearing loss]].

{{Multiple image | width = 145
| image1 = Otitis chron mesotymp 4.jpg
| caption1 = Perforation ([[otoscope]])
| image2 = Otitis media entdifferenziert2.jpg
| caption2 = Fluid in middle ear cavity
| footer = [[Otitis media]] complications can lead to hearing loss.
}}
Causes of conductive hearing loss include an ear canal blocked by earwax, ossicles that are fixed together or absent, or holes in the eardrum. Conductive hearing loss may also result from middle ear inflammation causing fluid build-up in the normally air-filled space, such as by [[otitis media]]. [[Tympanoplasty]] is the general name of the operation to repair the middle ear's eardrum and ossicles. Grafts from muscle fascia are ordinarily used to rebuild an intact eardrum. Sometimes artificial ear bones are placed to substitute for damaged ones, or a disrupted ossicular chain is rebuilt in order to conduct sound effectively.

[[Hearing aid]]s or [[cochlear implant]]s may be used if the hearing loss is severe or prolonged. Hearing aids work by amplifying the sound of the local environment and are best suited to conductive hearing loss.<ref>{{Cite web|url=https://www.nidcd.nih.gov/health/hearing-aids|title=Hearing Aids|website=National institute of deafness and other communication disorders|access-date=20 March 2016}}</ref> Cochlear implants transmit the sound that is heard as if it were a nervous signal, bypassing the cochlea. Active [[middle ear implant]]s send sound vibrations to the ossicles in the middle ear, bypassing any non-functioning parts of the outer and middle ear.

===Congenital abnormalities===
Anomalies and malformations of the auricle are common. These anomalies include chromosome syndromes such as [[ring 18]]. Children may also present cases of abnormal ear canals and low ear implantation.<ref name=moore2008/> In rare cases, no auricle is formed ([[Aural atresia|atresia]]), or is extremely small ([[microtia]]). Small auricles can develop when the auricular hillocks do not develop properly. The ear canal can fail to develop if it does not channelise properly or if there is an obstruction.<ref name=moore2008/> Reconstructive surgery to treat hearing loss is considered as an option for children older than five,<ref name=kliegman2007>{{cite book |last1=Kliegman |last2=Behrman |last3= Jenson |year=2007 |title=Nelson Textbook of Pedriatics |chapter=367}}</ref> with a cosmetic surgical procedure to reduce the size or change the shape of the ear is called an [[otoplasty]]. The initial medical intervention is aimed at assessing the baby's hearing and the condition of the ear canal, as well as the middle and inner ear. Depending on the results of tests, reconstruction of the outer ear is done in stages, with planning for any possible repairs of the rest of the ear.<ref>Lam SM. Edward Talbot Ely: father of aesthetic otoplasty. [Biography. Historical Article. Journal Article] Archives of Facial Plastic Surgery. 6(1):64, 2004 Jan–Feb.</ref><ref>Siegert R. Combined reconstruction of congenital auricular atresia and severe microtia. [Evaluation Studies. Journal Article] Laryngoscope. 113(11):2021–2027; discussion 2028–2029, 2003 Nov.</ref><ref>Trigg DJ. Applebaum EL. Indications for the surgical repair of unilateral aural atresia in children. [Review] [33 refs] [Journal Article. Review], American Journal of Otology. 19(5):679–684; discussion 684–686, 1998 September</ref>

Approximately one out of one thousand children suffer some type of congenital deafness related to the development of the inner ear.<ref name=lalwani2009>{{cite book |last=Lalwani |first=A.K. |author-link=A.K. Lalwani |year=2009 |title=Diagnóstico y tratamiento en Otorrinolaringología. Cirugía de Cabeza y Cuello |pages=624–752}}</ref> Inner ear congenital anomalies are related to sensorineural hearing loss and are generally diagnosed with a [[computed tomography]] (CT) scan or a [[magnetic resonance imaging]] (MRI) scan.<ref name=kliegman2007/> Hearing loss problems also derive from inner ear anomalies because its development is separate from that of the middle and external ear.<ref name=moore2008/> Middle ear anomalies can occur because of errors during head and neck development. The first pharyngeal pouch syndrome associates middle ear anomalies to the malleus and incus structures as well as to the non-differentiation of the [[annular stapedial ligament]]. Temporal bone and ear canal anomalies are also related to this structure of the ear and are known to be associated with sensorineural hearing loss and conductive hearing loss.<ref name=kliegman2007/>

===Vertigo===
{{Main|Vertigo}}
Vertigo refers to the inappropriate perception of motion. This is due to dysfunction of the [[vestibular system]]. One common type of vertigo is [[benign paroxysmal positional vertigo]], when an [[otolith]] is displaced from the ventricles to the semicircular canal. The displaced otolith rests on the cupola, causing a sensation of movement when there is none. [[Ménière's disease]], [[labyrinthitis]], [[stroke]]s, and other infective and congenital diseases may also result in the perception of vertigo.<ref>{{cite book|<!-- last1=Britton|first1=the editors Nicki R. Colledge, Brian R. Walker, Stuart H. Ralston; illustrated by Robert| -->title=Davidson's principles and practice of medicine.|date=2010|publisher=Churchill Livingstone/Elsevier|location=Edinburgh|isbn=978-0-7020-3084-0|pages=1151–1171|edition=21st }}</ref>

===Injury===
;Outer ear
Injuries to the external ear occur fairly frequently, and can leave minor to major deformity. Injuries include: [[laceration]], [[avulsion injuries]], [[burn]] and repeated twisting or pulling of an ear, for discipline or torture.<ref name=Alexandru2004>{{Cite journal
| last = Alexandru
| first = Florin
| date = 30 January 2004
| title = Ear Injuries
| url = http://www.cpt.coe.int/en/working-documents/cpt-2004-12-eng.pdf
| journal = Council of Europe
}}</ref> Chronic damage to the ears can cause [[cauliflower ear]], a common condition in [[boxing|boxers]] and [[wrestling|wrestlers]] in which the cartilage around the ears becomes lumpy and distorted owing to persistence of a [[haematoma]] around the [[perichondrium]], which can impair blood supply and healing.<ref>{{Cite web
| url = https://www.merckmanuals.com/home/injuries-and-poisoning/facial-injuries/ear-injury
| title = Ear Injury – Injuries and Poisoning
| website = Merck Manuals Consumer Version
| access-date = 2016-02-25
}}</ref> Owing to its exposed position, the external ear is susceptible to [[frostbite]]<ref>{{Cite book
| title = Davidson's Principles and Practice of Medicine
| last = Colledge
| first = Nicki
| publisher = Churchill Livingstone
| year = 2010
| pages = 102
}}</ref> as well as [[skin cancer]]s, including [[squamous-cell carcinoma]] and [[basal-cell carcinoma]]s.<ref>{{Cite web
 |url=http://www.skincancer.org/skin-cancer-information/basal-cell-carcinoma/the-ears-a-high-risk-area-for-skin-cancer
 |title=The Ears, A High Risk Area for Skin Cancer
 |website=www.skincancer.org
 |access-date=2016-02-25
 |url-status=dead
 |archive-url=https://web.archive.org/web/20160304145249/http://www.skincancer.org/skin-cancer-information/basal-cell-carcinoma/the-ears-a-high-risk-area-for-skin-cancer
 |archive-date=4 March 2016
 }}</ref>

;Middle ear
The ear drum may become perforated in the event of a large sound or explosion, when diving or flying (called [[barotrauma]]), or by objects inserted into the ear. Another common cause of injury is due to an infection such as otitis media.<ref>{{Cite web
| url = http://www.webmd.com/pain-management/ruptured-eardrum-symptoms-and-treatments
| title = Ruptured Eardrum: Symptoms, Treatments, and Recovery
| website = WebMD
| language = en-US
| access-date = 2016-02-25
}}</ref> These may cause a discharge from the ear called [[otorrhea]],<ref>{{Cite web
| url = http://www.medscape.com/viewarticle/766184_2
| title = How should I evaluate a draining ear?
| website = Medscape
| access-date = 2016-02-25
}}</ref> and are often investigated by [[Otoscope|otoscopy]] and [[audiometry]]. Treatment may include [[watchful waiting]], antibiotics and possibly surgery, if the injury is prolonged or the position of the ossicles is affected.<ref>{{Cite web
| url = https://www.merckmanuals.com/professional/ear,-nose,-and-throat-disorders/middle-ear-and-tympanic-membrane-disorders/traumatic-perforation-of-the-tympanic-membrane
| title = Traumatic Perforation of the Tympanic Membrane – Ear, Nose, and Throat Disorders
| website = Merck Manuals Professional Edition
| access-date = 2016-02-25
}}</ref> Skull fractures that go through the part of the skull containing the ear structures (the temporal bone) can also cause damage to the middle ear.<ref>{{Cite web
| url = http://www.uptodate.com/contents/evaluation-and-management-of-middle-ear-trauma
| title = Evaluation and management of middle ear trauma
| website = www.uptodate.com
| access-date = 2016-02-25
}}</ref> A [[cholesteatoma]] is a cyst of squamous skin cells that may develop from birth or secondary to other causes such as chronic ear infections. It may impair hearing or cause dizziness or vertigo, and is usually investigated by otoscopy and may require a CT scan. The treatment for cholesteatoma is surgery.<ref>{{Cite web
| url = https://medlineplus.gov/ency/article/001050.htm
| title = Cholesteatoma: MedlinePlus Medical Encyclopedia
| website = www.nlm.nih.gov
| access-date = 2016-02-25
}}</ref>

;Inner ear
There are two principal damage mechanisms to the inner ear in industrialised society, and both injure hair cells. The first is exposure to elevated sound levels (noise trauma), and the second is exposure to drugs and other substances ([[ototoxicity]]). A large number of people are exposed to sound levels on a daily basis that are likely to lead to significant [[noise health effects|hearing loss]].<ref>Senate Public Works Committee, Noise Pollution and Abatement Act of 1972, S. Rep. No. 1160, 92nd Cong. 2nd session.</ref> The [[National Institute for Occupational Safety and Health]] has recently published research on the estimated numbers of persons with hearing difficulty (11%) and the percentage of those that can be attributed to occupational noise exposure (24%).<ref>Tak SW, Calvert GM, "Hearing Difficulty Attributable to Employment by Industry and Occupation: An Analysis of the National Health Interview Survey – United States, 1997 to 2003", J. Occup. Env. Med. 2008, 50:46–56</ref> Furthermore, according to the [[National Health and Nutrition Examination Survey]] (NHANES), approximately twenty-two million (17%) US workers reported exposure to hazardous workplace noise.<ref>{{cite journal | last1 = Tak | first1 = SW | last2 = Davis | first2 = RR | last3 = Calvert | first3 = GM | year = 2009 | title = Exposure to Hazardous Workplace Noise and Use of Hearing Protection Devices Among US WOrkers, 1999–2004 | url = https://zenodo.org/record/1229079| journal = Am. J. Ind. Med. | volume = 52 | issue = 5| pages = 358–371 | doi=10.1002/ajim.20690 | pmid = 19267354| doi-access = free }}</ref> Workers exposed to hazardous noise further exacerbate the potential for developing [[noise-induced hearing loss]] when they do not wear [[hearing protection]].

=== Tinnitus ===
[[Tinnitus]] is the hearing of [[sound]] when no external sound is present.<ref name=Lev2015>{{cite book|last1=Levine|first1=RA|last2=Oron|first2=Y|chapter=Tinnitus |title=The Human Auditory System - Fundamental Organization and Clinical Disorders|date=2015|volume=129|pages=409–431|pmid=25726282|doi=10.1016/B978-0-444-62630-1.00023-8|series=Handbook of Clinical Neurology|isbn=978-0-444-62630-1}}</ref> While often described as a ringing, it may also sound like a clicking, hiss or roaring.<ref name=NIH2014/> Rarely, unclear voices or music are heard.<ref name=Lancet2013/> The sound may be soft or loud, low [[Pitch (music)|pitched]] or high pitched and appear to be coming from one ear or both.<ref name=NIH2014>{{cite web|title=Tinnitus|url=https://www.nidcd.nih.gov/health/tinnitus|access-date=22 May 2015|date=September 2014}}</ref> Most of the time, it comes on gradually.<ref name=Lancet2013>{{cite journal|last=Baguley|first=D|author2=McFerran, D|author3=Hall, D|title=Tinnitus.|journal=Lancet|date=9 November 2013|volume=382|issue=9904|pages=1600–1607|pmid=23827090|doi=10.1016/S0140-6736(13)60142-7|url=http://eprints.nottingham.ac.uk/3228/2/Hall-Tinnitus.pdf|access-date=30 June 2019|archive-date=11 April 2018|archive-url=https://web.archive.org/web/20180411174207/http://eprints.nottingham.ac.uk/3228/2/Hall-Tinnitus.pdf|url-status=dead}}</ref> In some people, the sound causes depression, anxiety, or concentration difficulties.<ref name=NIH2014/>

<!--Cause  -->Tinnitus is not a disease but a symptom that can result from a number of underlying causes.<!-- <ref name=NIH2014/> --> One of the most common causes is [[noise-induced hearing loss]].<!-- <ref name=NIH2014/> --> Other causes include: [[ear infection]]s, [[cardiovascular disease|disease of the heart or blood vessels]], [[Ménière's disease]], [[brain tumor]]s, [[Stress (psychological)|emotional stress]], exposure to certain medications, a previous [[head injury]], and earwax.<ref name=NIH2014/><ref>{{cite journal |journal=J Clin Neurol |date=March 2009 |volume=5 |issue=1 |pages=11–19 |pmc=2686891 |pmid=19513328 |title=Tinnitus: characteristics, causes, mechanisms, and treatments |vauthors=Han BI, Lee HW, Kim TY, Lim JS, Shin KS |quote=About 75% of new cases are related to emotional stress as the trigger factor rather than to precipitants involving cochlear lesions. |doi=10.3988/jcn.2009.5.1.11}}</ref> It is more common in those with depression and anxiety.<ref name=Lancet2013/>

===== Hyperacusis =====
[[Hyperacusis]] is a condition where sounds are painful, usually in the ear or from headaches.<ref>{{Cite web |title=Hyperacusis: Hearing Sensitivity Causes and Treatment |url=https://my.clevelandclinic.org/health/diseases/24320-hyperacusis |archive-url=http://web.archive.org/web/20250912061304/https://my.clevelandclinic.org/health/diseases/24320-hyperacusis |archive-date=2025-09-12 |access-date=2025-11-16 |website=Cleveland Clinic |language=en}}</ref>

==Society and culture==
[[File:Modified Ear.jpg|thumb|Stretching of the earlobe and various cartilage piercings]]

The ears have been ornamented with jewelry for thousands of years, traditionally by [[ear piercing|piercing]] of the [[earlobe]]. In ancient and modern cultures, ornaments have been placed to stretch and enlarge the earlobes, allowing for larger [[plug (jewellery)|plugs]] to be slid into a large fleshy gap in the lobe. Tearing of the earlobe from the weight of heavy [[earring]]s, or from traumatic pull of an earring (for example, by snagging on a sweater), is fairly common.<ref>{{cite book | url = https://books.google.com/books?id=ljeY_Tvyl_MC&q=earlobe+tear+earring&pg=PA60 | title = Instant Beauty: Getting Gorgeous on Your Lunch Break |author1=Deborah S. Sarnoff |author2=Robert H. Gotkin |author3=Joan Swirsky | publisher = St. Martin's Press | year = 2002 | isbn = 0-312-28697-X }}</ref>

Injury to the ears has been present since Roman times as a method of reprimand or punishment – "In Roman times, when a dispute arose that could not be settled amicably, the injured party cited the name of the person thought to be responsible before the Praetor; if the offender did not appear within the specified time limit, the complainant summoned witnesses to make statements.  If they refused, as often happened, the injured party was allowed to drag them by the ear and to pinch them hard if they resisted.  Hence the French expression "{{Lang|fr|se faire tirer l’oreille}}", of which the literal meaning is "to have one's ear pulled" and the figurative meaning "to take a lot of persuading". We use the expression "to tweak (or pull) someone's ears"  to mean "inflict a punishment"."<ref name=Alexandru2004 />

The auricles have an effect on facial appearance. In Western societies, protruding ears (present in about 5% of ethnic [[European ethnic groups|Europeans]]) have been considered unattractive, particularly if asymmetric.<ref>{{Cite book
| url = https://books.google.com/books?id=j0_r6YZIvbYC
| title = Advanced Therapy in Facial Plastic and Reconstructive Surgery
| last = Thomas
| first = J. Regan
| date = 2010
| publisher = PMPH-USA
| isbn = 978-1-60795-011-0
| page = 513
| language = en
}}</ref> The first surgery to reduce the projection of prominent ears was published in the medical literature by [[Ernst Dieffenbach]] in 1845, and the first [[case report]] in 1881.<ref>{{Cite book
| url = https://books.google.com/books?id=uzZhODdfn8gC
| title = Peterson's Principles of Oral and Maxillofacial Surgery
| last1 = Miloro
| first1 = Michael
| last2 = Ghali
| first2 = G.E.
| last3 = Larsen
| first3 = Peter
| last4 = Waite
| first4 = Peter
| date = 2004
| publisher = PMPH-USA
| isbn = 978-1-55009-234-9
| language = en
| chapter = Chapter 71. Otoplastic surgery for the protruding ear.
}}</ref>

[[Pointy ears#Humans|Pointy ears]] are a characteristic of some creatures in [[folklore]] such as the French [[croquemitaine]], Brazilian [[curupira]]<ref name="Bane2013">{{cite book|author=Theresa Bane|title=Encyclopedia of Fairies in World Folklore and Mythology|url=https://books.google.com/books?id=rUqpAAAAQBAJ&pg=PA91|year=2013|publisher=McFarland|isbn=978-0-7864-7111-9|page=91}}</ref> or Japanese [[earth spider]].{{citation needed|date=January 2023}} It has been a feature of characters on art as old as that of [[Ancient Greece]]<ref name="Winckelmann1850">{{cite book|author=Johann Joachim Winckelmann|title=The History of Ancient Art Among the Greeks|url=https://archive.org/details/historyancienta00lodggoog|year=1850|publisher=Chapman|page=[https://archive.org/details/historyancienta00lodggoog/page/n115 80]}}</ref> and [[medieval Europe]].<ref name="Bovey2002">{{cite book|author=Alixe Bovey|title=Monsters and Grotesques in Medieval Manuscripts|url=https://books.google.com/books?id=8rytlDZ4xdgC&pg=PA38|year=2002|publisher=University of Toronto Press|isbn=978-0-8020-8512-2|page=38}}</ref> Pointy ears are a common characteristic of many creatures in the [[fantasy]] genre,<ref name="Peffer2012">{{cite book|author=J. Peffer|title=DragonArt Collector's Edition: Your Ultimate Guide to Drawing Fantasy Art|url=https://books.google.com/books?id=jcPqm5smoMMC&pg=PA28|year=2012|publisher=IMPACT|isbn=978-1-4403-2417-8|page=28}}</ref> including [[elves]],<ref name="Tresca2010">{{cite book|author=Michael J. Tresca|title=The Evolution of Fantasy Role-Playing Games|url=https://books.google.com/books?id=8H8bzqj6S4sC&pg=PA34|year=2010|publisher=McFarland|isbn=978-0-7864-6009-0|page=34}}</ref><ref name="Okum2006">{{cite book|author=David Okum|title=Manga Fantasy Madness: Over 50 Basic Lessons for Drawing Warriors, Wizards, Monsters and more|url=https://books.google.com/books?id=_4aPjotgxJcC&pg=PA31|year=2006|publisher=IMPACT|isbn=1-60061-381-0|page=31}}</ref><ref name="Knight2005">{{cite book|author=Sirona Knight|title=The Complete Idiot's Guide to Elves and Fairies|url=https://books.google.com/books?id=7m5s8HmpSp8C&pg=PT171|date=7 June 2005|publisher=DK Publishing|isbn=978-1-4406-9638-1|page=171}}</ref> [[faeries]],<ref name="Greer2011">{{cite book|author=John Michael Greer|title=Monsters|url=https://books.google.com/books?id=qDda4Q27kXYC&pg=PT107|date=1 September 2011|publisher=Llewellyn Worldwide|isbn=978-0-7387-1600-8|page=107}}</ref><ref name="Hart2008">{{cite book|author=Christopher Hart|title=Astonishing Fantasy Worlds: The Ultimate Guide to Drawing Adventure Fantasy Art|url=https://books.google.com/books?id=geE2AQAAIAAJ|year=2008|publisher=Watson-Guptill Publications|isbn=978-0-8230-1472-9|page=103}}</ref> [[pixie]]s,<ref name="Hamilton2011">{{cite book|author=John Hamilton|title=Elves and Fairies|url=https://books.google.com/books?id=glzvoVQwqwoC&pg=PA23|date=1 August 2011|publisher=ABDO|isbn=978-1-60453-215-9|page=23}}</ref> [[hobbit]]s,<ref name="KavkaLawn2006">{{cite book|author1=Misha Kavka|author2=Jenny Lawn|author3=Mary Paul|title=Gothic Nz: The Darker Side of Kiwi Culture|url=https://books.google.com/books?id=pshlAAAAMAAJ|year=2006|publisher=Otago University Press|isbn=978-1-877372-23-0|page=111}}</ref> or [[orcs]].<ref name="Hopkins2010">{{cite book|author=Lisa Hopkins|title=Screening the Gothic|url=https://books.google.com/books?id=4dmGAAAAQBAJ&pg=PT202|date=1 January 2010|publisher=University of Texas Press|isbn=978-0-292-77959-4|page=202}}</ref> They are a characteristic of creatures in the [[horror literature|horror]] genre, such as [[vampire]]s.<ref name="Isenberg2013">{{cite book|author=Noah William Isenberg|title=Weimar Cinema: An Essential Guide to Classic Films of the Era|url=https://books.google.com/books?id=A9vbWimrmcEC&pg=PT96|date=13 August 2013|publisher=Columbia University Press|isbn=978-0-231-50385-3|pages=96–}}</ref><ref name="Gelder2000">{{cite book|author=Ken Gelder|title=The Horror Reader|url=https://books.google.com/books?id=upGM6haNBR8C&pg=PA27|year=2000|publisher=Psychology Press|isbn=978-0-415-21356-1|page=27}}</ref> Pointy ears are also found in the [[science fiction]] genre; for example among the [[Vulcan (Star Trek)|Vulcan]] and [[Romulan]] races of the ''[[Star Trek]]'' universe<ref name="IIIMcPherson2003">{{cite book|author1=Henry Jenkins III|author2=Tara McPherson|author3=Jane Shattuc|title=Hop on Pop: The Politics and Pleasures of Popular Culture|url=https://books.google.com/books?id=ZZSz3ThOv9gC&pg=PA119|date=2 January 2003|publisher=Duke University Press|isbn=0-8223-8350-0|page=119}}</ref> and the [[Nightcrawler (character)|Nightcrawler]] character from the [[X-Men]] universe.<ref name="IrwinHousel2009">{{cite book|author1=William Irwin|author2=Rebecca Housel|author3=J. Jeremy Wisnewski|title=X-Men and Philosophy: Astonishing Insight and Uncanny Argument in the Mutant X-Verse|url=https://books.google.com/books?id=bK-ax5Ttj3wC&pg=PA189|date=18 May 2009|publisher=John Wiley & Sons|isbn=978-0-470-73036-2|page=189}}</ref>

[[Georg von Békésy]] was a Hungarian [[Biophysics|biophysicist]] born in [[Budapest]], [[Hungary]]. In 1961, he was awarded the [[Nobel Prize in Physiology or Medicine]] for his research on the function of the [[cochlea]] in the mammalian hearing organ.<ref>{{cite journal|author=Stevens, S.S. |author-link=Stanley Smith Stevens |title=Georg von Békésy |journal=Physics Today |date=September 1972 |volume=25 |issue=9 |pages=78–80 |url=http://www.physicstoday.org/resource/1/phtoad/v25/i9/p78_s1?bypassSSO=1 |archive-url=https://archive.today/20130924145118/http://www.physicstoday.org/resource/1/phtoad/v25/i9/p78_s1?bypassSSO=1 |url-status=dead |archive-date=2013-09-24 |doi=10.1063/1.3071029 |bibcode=1972PhT....25i..78S |url-access=subscription }}</ref>

The [[Vacanti mouse]] was a laboratory [[mouse]] that had what looked like a human ear grown on its back. The "ear" was actually an ear-shaped [[cartilage]] structure grown by seeding cow cartilage cells into a biodegradable ear-shaped mold and then implanted under the skin of the mouse; then the cartilage naturally grew by itself.<ref>{{Cite journal
| doi = 10.1097/00006534-199708000-00001
| last1 = Cao | first1 = Y.
| last2 = Vacanti | first2 = J.P.
| last3 = Paige | first3 = K.T.
| last4 = Upton | first4 = J.
| last5 = Vacanti | first5 = C.A.
| title = Transplantation of chondrocytes utilizing a polymer-cell construct to produce tissue-engineered cartilage in the shape of a human ear
| journal = [[Plastic and Reconstructive Surgery]]
| volume = 100
| issue = 2
| pages = 297–302; discussion 303–304
| year = 1997
| pmid = 9252594
| s2cid = 41167703 }}</ref> It was developed as an alternative to ear repair or grafting procedures and the results met with much publicity and controversy in 1997.<ref>{{cite news|last1=Goodyear|first1=Dana|title=The Stress Test|url=http://www.newyorker.com/magazine/2016/02/29/the-stem-cell-scandal |date=February 21, 2016 |url-access=subscription |access-date=23 March 2016|agency=New Yorker |url-status=live |archive-url=https://archive.is/3oQg9 |archive-date= 24 Feb 2016 }}</ref><ref>{{cite book|author1=Karin Sellberg, Lena Wånggren|title=Corporeality and Culture: Bodies in Movement|date=2016|publisher=Routledge|isbn=978-1-317-15924-7|pages=75–76|url=https://books.google.com/books?id=fL21CwAAQBAJ&q=earmouse+1997+controversy&pg=PT75}}</ref>

==Other animals==
[[File:Darwin-s-tubercle.jpg|thumb|left|220px|{{center|[[Primate]] ears<br />Human and [[crab-eating macaque]]<br /><small>([[Darwin's tubercle]] highlighted)</small>}}]]
[[File:Haeckel Chiroptera.jpg|thumb|200px|{{center|Pinnae of [[bat]]s}}]]
The ears of [[vertebrate]]s are placed somewhat symmetrically on either side of the head, an arrangement that aids [[sound localization]].

All mammals have [[Evolution of mammalian auditory ossicles|three auditory ossicles]]. The external [[Pinna (anatomy)|pinna]] in [[theria]]n mammals helps direct sound through the ear canal to the eardrum. The complex geometry of ridges on the inner surface of some mammalian ears helps to sharply focus sounds produced by prey, using echolocation signals. These ridges can be regarded as the acoustic equivalent of a [[Fresnel lens]], and may be seen in a wide range of animals, including the [[bat]], [[aye-aye]], [[lesser galago]], [[bat-eared fox]], [[mouse lemur]] and others.<ref>{{cite journal  | doi = 10.2307/3546476  | last1 = Pavey | first1 = C.R.  | last2 = Burwell | first2 = C.J.  | year = 1998  | title = Bat Predation on Eared Moths: A Test of the Allotonic Frequency Hypothesis  | journal = Oikos  | volume = 81  | issue = 1  | pages = 143–151  | jstor = 3546476 | bibcode = 1998Oikos..81..143P }}</ref><ref>{{Cite web |url=http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA164098 |title=The Bat's Ear as a Diffraction Grating<!-- Bot generated title --> |access-date=27 October 2011 |archive-url=https://web.archive.org/web/20120418224928/http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA164098 |archive-date=18 April 2012 |url-status=dead }}</ref><ref>{{Cite journal
| last1 = Kuc | first1 = R.
| title = Model predicts bat pinna ridges focus high frequencies to form narrow sensitivity beams
| doi = 10.1121/1.3097500
| journal = The Journal of the Acoustical Society of America
| volume = 125
| issue = 5
| pages = 3454–3459
| year = 2009
| pmid = 19425684
| bibcode = 2009ASAJ..125.3454K
}}</ref>

Some large [[primate]]s such as [[gorilla]]s and [[orangutan]]s (and also [[human]]s) have undeveloped ear [[muscle]]s that are non-functional [[vestigial structure]]s, yet are still large enough to be easily identified.<ref name="Descent">[[Charles Darwin|Darwin, Charles]] (1871). ''[[The Descent of Man, and Selection in Relation to Sex]]''. John Murray: London.</ref> An ear muscle that cannot move the ear, for whatever reason, has lost that biological function. [[File:Man able to move him ear 8jo WATANABE Hachijo.gif|thumb|Man able to move his ear]]This serves as evidence of [[homology (biology)|homology]] between related species. In humans, there is variability in these muscles, such that some people are able to move their ears in various directions, and it has been said that it may be possible for others to gain such movement by repeated trials.<ref name="Descent"/> In such primates, the inability to move the ear is compensated for mainly by the ability to easily turn the [[head]] on a horizontal plane, an ability which is not common to most monkeys—a function once provided by one structure is now replaced by another.<ref>Mr. St. George Mivart, Elementary Anatomy, 1873, p. 396.  Two ears provide stereo imaging that the brain can use to develop a 3-dimensional sound field.</ref>

In some animals with mobile pinnae (like the horse), each pinna can be aimed independently to better receive the sound. For these animals, the pinnae help [[sound localization|localise the direction of the sound source]].
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<gallery class="left" mode="packed" heights="160px" widths="160px">
File:Elephant near ndutu.jpg|{{center|[[African bush elephant]]<br />''Loxodonta africana''}}
File:2009-03-07Vulpes zerda016.jpg|{{center|[[Fennec fox]] (desert regions)<br />''Vulpes zerda''}}
Image:Iceland-1979445.jpg|{{center|[[Arctic fox]]<br />''Vulpes lagopus''}}
File:Rabbit - French Lop breed.jpg|{{center|[[Domestic rabbit]] – [[French Lop]] breed<br />''Oryctolagus cuniculus''}}
</gallery>

[[File:Darwin Domestic 105.png|thumb|right|{{center|<small>Half-Lop Rabbit<br />''Illustration by<br />Charles Darwin, 1868''</small>}}|180px]]
The ear, with its blood vessels close to the surface, is an essential thermoregulator in some land mammals, including the elephant, the fox, and the rabbit.<ref>{{Cite journal|last1=Fayez|first1=I.|last2=Marai|first2=M.|last3=Alnaimy|first3=A.|last4=Habeeb|first4=M.|editor-last=Baselga|editor-first=M.|editor2-last=Marai|editor2-first=I.F.M.|title=Thermoregulation in Rabbits|url=http://ressources.ciheam.org/om/pdf/c08/95605277.pdf|journal=Rabbit Production in Hot Climates|series=Cahiers Options Méditerranéennes|location=Zaragoza|publisher=CIHEAM – International Centre for Advanced Mediterranean Agronomic Studies|date=1994|volume=8|pages=33–41|access-date=25 February 2018|archive-date=6 October 2021|archive-url=https://web.archive.org/web/20211006131148/http://ressources.ciheam.org/om/pdf/c08/95605277.pdf|url-status=dead}}</ref> There are five types of [[Lop rabbit#Ear type|ear carriage]] in domestic rabbits, some of which have been bred for exaggerated ear length<ref>{{cite web|title=Longest ears on a rabbit|url=http://www.guinnessworldrecords.com/world-records/longest-ears-on-a-rabbit|website=Guinness World Records|date=November 2003 |access-date=9 February 2018}}</ref>—a potential health risk that is controlled in some countries.<ref name="Whitman">{{cite book|last1=Whitman|first1=Bob D.|title=Domestic Rabbits & Their Histories: Breeds of the World|date=October 2004|publisher=Leathers Publishing|location=Leawood KS|isbn=978-1-58597-275-3}}</ref> Abnormalities in the skull of a half-lop rabbit were [[s:The Variation of Animals and Plants under Domestication|studied by Charles Darwin]] in 1868. In marine mammals, [[earless seal]]s are one of three groups of [[Pinniped]]ia.

===Invertebrates===
Only vertebrate animals have ears, though many invertebrates detect sound using other kinds of sense organs. In insects, [[tympanal organ]]s are used to hear distant sounds. They are located either on the head or elsewhere, depending on the insect [[Family (biology)|family]].<ref>{{cite journal | last1 = Yack | first1 = JE | last2 = Fullard | first2 = JH | year = 1993 | title = What is an insect ear? | journal = Ann. Entomol. Soc. Am. | volume = 86 | issue = 6| pages = 677–682 | doi = 10.1093/aesa/86.6.677 }}</ref> The tympanal organs of some insects are extremely sensitive, offering acute hearing beyond that of most other animals. The female cricket fly ''[[Ormia ochracea]]'' has tympanal organs on each side of her abdomen. They are connected by a thin bridge of exoskeleton and they function like a tiny pair of eardrums, but, because they are linked, they provide acute directional information. The fly uses her "ears" to detect the call of her host, a male cricket. Depending on where the song of the cricket is coming from, the fly's hearing organs will reverberate at slightly different frequencies. This difference may be as little as 50&nbsp;billionths of a second, but it is enough to allow the fly to home in directly on a singing male cricket and parasitise it.<ref>[[Ross Piper|Piper, Ross]] (2007), ''Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals'', [[Greenwood Press]].</ref>

Simpler structures allow other [[arthropod]]s to detect [[wikt:near-field|near-field]] sounds. Spiders and cockroaches, for example, have hairs on their legs, which are used for detecting sound. Caterpillars may also have hairs on their body that perceive vibrations<ref>Scoble, M.J. 1992. The Lepidoptera: Form, function, and diversity. [[Oxford University Press]]</ref> and allow them to respond to sound.

==See also==
* [[Hear, hear]]
* [[Hearing test]]
* [[Righting reflex]]
* [[Eustachian tube]] &ndash; The tube which connects the middle ear to the throat

==References==
{{Reflist}}

==External links==
* {{wiktionary inline}}
* {{Commons category-inline|Ears}}

{{Auditory and vestibular anatomy}}
{{Human regional anatomy}}
{{Authority control}}

[[Category:Ear| ]]
[[Category:Articles containing video clips]]
[[Category:Auditory system]]
[[Category:Human head and neck]]
[[Category:Sensory organs|Ear]]