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In , an ear is the organ that enables hearing and (in ) 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 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. The middle ear includes the tympanic cavity and the three . The inner ear sits in the bony labyrinth, and contains structures which are key to several senses: the semicircular canals, which enable balance and eye tracking when moving; the 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 and six small swellings that develop in the early embryo called , 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 and other jewelry in numerous cultures for thousands of years, and has been subjected to surgical and cosmetic alterations.
The auricle consists of the curving outer rim called the helix, the inner curved rim called the antihelix, and opens into the ear canal. The 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 1inch (2.5cm). 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 and that produce protective earwax. Earwax naturally migrates outward through ear canal, constituting a self-cleaning system.
Two sets of muscles are associated with the outer ear: the intrinsic and extrinsic muscles. In some mammals, these muscles can adjust the direction of the pinna. In humans, these muscles have little or no effect. (2025). 9781451184471, Lippincott Williams & Wilkins. ISBN 9781451184471 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 nerve, auriculotemporal nerve, and lesser and greater occipital nerves of the cervical plexus all supply sensation to parts of the outer ear and the surrounding skin.
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, 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 areola and adipose tissue.Stenström, J. Sten: Deformities of the ear; In: Grabb, W., C., Smith, J.S. (Edited): "Plastic Surgery", Little, Brown and Company, Boston, 1979, (C), (P) The symmetrical arrangement of the two ears allows for the localisation of sound. The brain accomplishes this by comparing arrival-times and intensities from each ear, in circuits located in the superior olivary complex and the Trapezoid body, which are connected via pathways to both ears. (2025). 9780878936977, Sinauer. ISBN 9780878936977
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.
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.
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. responsible for transduction—changing mechanical changes into electrical stimuli are present in the organ of Corti in the cochlea.
The outer ear is supplied by a number of arteries. The posterior auricular artery provides the majority of the blood supply. The 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.
The middle ear is supplied by the mastoid branch of either the occipital artery or 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.
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.
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 to dampen excessive vibrations. Vibration of the oval window causes vibration of the endolymph within the vestibule and the cochlea.
The inner ear houses the apparatus necessary to 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 that release a chemical neurotransmitter when stimulated. Sound waves moving through fluid flows against the 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.
The human ear can generally hear sounds with frequencies between 20 Hertz and 20 kHz (the audio range). Sounds outside this range are considered infrasound (below 20 Hz)Greinwald, John H. Jr MD; Hartnick, Christopher J. MD The Evaluation of Children With Sensorineural Hearing Loss. Archives of Otolaryngology–Head & Neck Surgery. 128(1):84–87, January 2002 or ultrasound (above 20 kHz) 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.
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 , tiny formations of calcium carbonate. When a person moves, these otoliths shift position. This shift alters the positions of the filaments, which opens within the cell membranes, creating depolarisation and an action potential that is transmitted to the brain along the vestibulocochlear nerve.
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, which contains numerous cells with filaments in a central area called the ampullary 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. Dynamic balance also helps maintain eye tracking when moving, via the vestibulo-ocular reflex.
Around the 28th day, parts of the otic vesicle begin to form the vestibulocochlear nerve. These form , 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).
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.
As the cochlear duct's mesenchyme begins to differentiate, three cavities are formed: the scala vestibuli, the scala tympani and the scala media. Both the scala vestibuli and the scala tympani contain an extracellular fluid called perilymph, while the scala media contains endolymph. The vestibular membrane and the basilar membrane develop to separate the cochlear duct from the vestibular duct and the tympanic duct, respectively.
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.
or 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. Cochlear implants transmit the sound that is heard as if it were a nervous signal, bypassing the cochlea. Active middle ear implants send sound vibrations to the ossicles in the middle ear, bypassing any non-functioning parts of the outer and middle ear.
Approximately one out of one thousand children suffer some type of congenital deafness related to the development of the inner ear. 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. Hearing loss problems also derive from inner ear anomalies because its development is separate from that of the middle and external ear. 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.
Tinnitus is not a disease but a symptom that can result from a number of underlying causes. One of the most common causes is noise-induced hearing loss. Other causes include: , disease of the heart or blood vessels, Ménière's disease, , emotional stress, exposure to certain medications, a previous head injury, and earwax. It is more common in those with depression and anxiety.
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 "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"."
The auricles have an effect on facial appearance. In Western societies, protruding ears (present in about 5% of ethnic Europeans) have been considered unattractive, particularly if asymmetric. 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.
Pointy ears are a characteristic of some creatures in folklore such as the French croquemitaine, Brazilian curupira or Japanese earth spider. It has been a feature of characters on art as old as that of Ancient Greece and medieval Europe. Pointy ears are a common characteristic of many creatures in the fantasy genre, including elves, faeries, , , or orcs. They are a characteristic of creatures in the horror genre, such as . Pointy ears are also found in the science fiction genre; for example among the Vulcan and Romulan races of the Star Trek universe and the Nightcrawler character from the X-Men universe.
Georg von Békésy was a Hungarian Biophysics 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.
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. It was developed as an alternative to ear repair or grafting procedures and the results met with much publicity and controversy in 1997.
All mammals have three auditory ossicles. The external pinna in 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.
Some large such as and (and also ) have undeveloped ear that are non-functional vestigial structures, yet are still large enough to be easily identified.Charles Darwin (1871). The Descent of Man, and Selection in Relation to Sex. John Murray: London. An ear muscle that cannot move the ear, for whatever reason, has lost that biological function. serves as evidence of 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. 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.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.
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 localise the direction of the sound source.
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. There are five types of ear carriage in domestic rabbits, some of which have been bred for exaggerated ear length—a potential health risk that is controlled in some countries.
Simpler structures allow other to detect 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 vibrationsScoble, M.J. 1992. The Lepidoptera: Form, function, and diversity. Oxford University Press and allow them to respond to sound.
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, , and other infective and congenital diseases may also result in the perception of vertigo. (2025). 9780702030840, Churchill Livingstone/Elsevier. ISBN 9780702030840
Injury
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. Chronic damage to the ears can cause cauliflower ear, a common condition in boxing and wrestling 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. Owing to its exposed position, the external ear is susceptible to frostbite as well as , including squamous-cell carcinoma and basal-cell carcinomas.
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. These may cause a discharge from the ear called otorrhea, and are often investigated by Otoscope and audiometry. Treatment may include watchful waiting, antibiotics and possibly surgery, if the injury is prolonged or the position of the ossicles is affected. 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. 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.
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 hearing loss.Senate Public Works Committee, Noise Pollution and Abatement Act of 1972, S. Rep. No. 1160, 92nd Cong. 2nd session. 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%).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 Furthermore, according to the National Health and Nutrition Examination Survey (NHANES), approximately twenty-two million (17%) US workers reported exposure to hazardous workplace noise. 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. (2025). 9780444626301 ISBN 9780444626301 While often described as a ringing, it may also sound like a clicking, hiss or roaring. Rarely, unclear voices or music are heard. The sound may be soft or loud, low pitched or high pitched and appear to be coming from one ear or both. Most of the time, it comes on gradually. In some people, the sound causes depression, anxiety, or concentration difficulties.
Society and culture
The ears have been ornamented with jewelry for thousands of years, traditionally by ear piercing of the earlobe. In ancient and modern cultures, ornaments have been placed to stretch and enlarge the earlobes, allowing for larger plugs to be slid into a large fleshy gap in the lobe. Tearing of the earlobe from the weight of heavy , or from traumatic pull of an earring (for example, by snagging on a sweater), is fairly common.
Other animals
The ears of are placed somewhat symmetrically on either side of the head, an arrangement that aids sound localization.
(2004). 9781585972753, Leathers Publishing. ISBN 9781585972753 Abnormalities in the skull of a half-lop rabbit were in 1868. In marine mammals, are one of three groups of .
Invertebrates
Only vertebrate animals have ears, though many invertebrates detect sound using other kinds of sense organs. In insects, are used to hear distant sounds. They are located either on the head or elsewhere, depending on the insect family. 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 billionths of a second, but it is enough to allow the fly to home in directly on a singing male cricket and parasitise it.Ross Piper (2007), Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals, Greenwood Press.
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