The outer ear, external ear, or auris externa is the external part of the
ear, which consists of the
auricle (also pinna) and the
ear canal
The ear canal (external acoustic meatus, external auditory meatus, EAM) is a pathway running from the outer ear to the middle ear. The adult human ear canal extends from the pinna (anatomy), pinna to the eardrum and is about in length and in di ...
. It gathers sound energy and focuses it on the eardrum (
tympanic membrane
In the anatomy of humans and various other tetrapods, the eardrum, also called the tympanic membrane or myringa, is a thin, cone-shaped membrane that separates the external ear from the middle ear. Its function is to transmit sound from the a ...
).
Structure
Auricle
The visible part is called the
auricle, also known as the
pinna, especially in other animals. It is composed of a thin plate of yellow
elastic cartilage
Elastic cartilage, fibroelastic cartilage or yellow fibrocartilage is a type of cartilage present in the pinnae (auricles) of the ear giving it shape, provides shape for the lateral region of the external auditory meatus, medial part of the aud ...
, covered with integument, and connected to the surrounding parts by ligaments and muscles; and to the commencement of the
ear canal
The ear canal (external acoustic meatus, external auditory meatus, EAM) is a pathway running from the outer ear to the middle ear. The adult human ear canal extends from the pinna (anatomy), pinna to the eardrum and is about in length and in di ...
by fibrous tissue. Many
mammal
Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur ...
s can move the pinna (with the
auriculares muscles) in order to
focus their hearing in a certain direction in much the same way that they can turn their
eyes. Most humans do not have this ability.
Ear canal
From the pinna, the
sound wave
In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid.
In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the ...
s move into the
ear canal
The ear canal (external acoustic meatus, external auditory meatus, EAM) is a pathway running from the outer ear to the middle ear. The adult human ear canal extends from the pinna (anatomy), pinna to the eardrum and is about in length and in di ...
(also known as the ''external acoustic meatus'') a simple tube running through to the
middle ear
The middle ear is the portion of the ear medial to the eardrum, and distal to the oval window of the cochlea (of the inner ear).
The mammalian middle ear contains three ossicles, which transfer the vibrations of the eardrum into waves in the ...
. This tube leads inward from the bottom of the auricula and conducts the vibrations to the tympanic cavity and amplifies frequencies in the range 3
kHz to 12 kHz.
Muscles
Intrinsic muscles
The intrinsic muscles of the external ear are:
* The
helicis major is a narrow vertical band situated upon the anterior margin of the
helix
A helix () is a shape like a corkscrew or spiral staircase. It is a type of smooth space curve with tangent lines at a constant angle to a fixed axis. Helices are important in biology, as the DNA molecule is formed as two intertwined helic ...
. It arises below, from the
spina helicis, and is inserted into the anterior border of the helix, just where it is about to curve backward.
* The
helicis minor is an oblique
fasciculus
''Fasciculus vesanus'' is an extinct species of stem-group ctenophores known from the Burgess Shale of British Columbia, Canada. It is dated to and belongs to middle Cambrian strata.
The species is remarkable for its two sets of long and shor ...
, covering the
crus helicis.
* The
tragicus
The tragicus (muscle of tragus or Valsalva muscle) is an intrinsic muscle of the outer ear.
It is a short, flattened vertical band on the lateral surface of the tragus.
While the muscle modifies the auricular shape only minimally in the majorit ...
is a short, flattened vertical band on the lateral surface of the
tragus. Also known as the mini lobe.
* The
antitragicus arises from the outer part of the antitragus, and is inserted into the
cauda helicis and
antihelix
The antihelix (anthelix) is a part of the visible ear; the pinna.
The antihelix is a curved prominence of cartilage parallel with and in front of the helix
A helix () is a shape like a corkscrew or spiral staircase. It is a type of smooth s ...
.
* The
transverse muscle is placed on the cranial surface of the
pinna. It consists of scattered fibers, partly tendinous and partly muscular, extending from the
eminentia conchae
Eminence may refer to:
Places
* Eminence, Arkansas, a place in Arkansas, U.S.
* Eminence, Indiana, U.S.
* Eminence, Kansas, U.S.
* Eminence, Kentucky, U.S.
* Eminence, Mississippi, in Covington County, Mississippi, U.S.
* Eminence, Missouri, U ...
to the prominence corresponding with the
scapha.
* The
oblique muscle also on the cranial surface, consists of a few fibers extending from the upper and back part of the
concha to the convexity immediately above it.
Extrinsic muscles
The auricular muscles (or extrinsic muscles) are the three
muscle
Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of mus ...
s surrounding the ''
auricula'' or outer ear:
*
anterior auricular muscle
*
superior auricular muscle
The superior auricular muscle is a muscle above the auricle of the outer ear. It originates from the epicranial aponeurosis, and inserts into the upper part of the medial surface of the auricle. It draws the auricle upwards.
Structure
The su ...
*
posterior auricular muscle
The posterior auricular muscle is a muscle behind the auricle of the outer ear. It arises from the mastoid part of the temporal bone, and inserts into the lower part of the cranial surface of the auricle of the outer ear. It draws the auricle ...
The superior muscle is the largest of the three, followed by the posterior and the anterior.
In some mammals these muscles can adjust the direction of the pinna. In humans these muscles possess very little action.
The auricularis anterior draws the auricula forward and upward, the auricularis superior slightly raises it, and the auricularis posterior draws it backward.
Function
One consequence of the configuration of the outer ear is selectively to boost the
sound pressure
Sound pressure or acoustic pressure is the local pressure deviation from the ambient (average or equilibrium) atmospheric pressure, caused by a sound wave. In air, sound pressure can be measured using a microphone, and in water with a hydrop ...
30- to 100-fold for frequencies around 3 kHz. This amplification makes humans most sensitive to frequencies in this range—and also explains why they are particularly prone to acoustical injury and hearing loss near this frequency. Most human speech sounds are also distributed in the bandwidth around 3 kHz.
Clinical significance
Malformations of the external ear can be a consequence of
hereditary disease, or exposure to environmental factors such as
radiation
In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes:
* ''electromagnetic radiation'', such as radio waves, microwaves, infrared, visi ...
,
infection
An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable di ...
. Such defects include:
*A
preauricular fistula, which is a long narrow tube, usually near the
tragus. This can be inherited as an
autosomal recessive
In genetics, dominance is the phenomenon of one variant ( allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant an ...
fashion and may suffer from chronic infection in later life.
* Cosmetic defects, such as very large ears, small ears.
* Malformation that may lead to functional impairment, such as
atresia
Atresia is a condition in which an orifice or passage in the body is (usually abnormally) closed or absent.
Examples of atresia include:
*Aural atresia, a congenital deformity where the ear canal is underdeveloped.
* Biliary atresia, a condition i ...
of the external auditory meatus or
aplasia of the pinna,
* Genetic
syndrome
A syndrome is a set of medical signs and symptoms which are correlated with each other and often associated with a particular disease or disorder. The word derives from the Greek language, Greek σύνδρομον, meaning "concurrence". When a sy ...
s, which include:
**
Konigsmark syndrome, characterised by small ears and atresia of the external auditory canal, causing
conductive hearing loss and inherited in an
autosomal recessive
In genetics, dominance is the phenomenon of one variant ( allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant an ...
manner.
**
Goldenhar syndrome, a combination of developmental abnormalities affecting the ears, eyes, bones of the skull, and vertebrae, inherited in an
autosomal dominant
In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and t ...
manner.
**
Treacher Collins syndrome, characterised by dysplasia of the auricle, atresia of the bony part of the auditory canal, hypoplasia of the auditory ossicles and tympanic cavity, and 'mixed' deafness (both
sensorineural
Sensorineural hearing loss (SNHL) is a type of hearing loss in which the root cause lies in the inner ear or sensory organ (cochlea and associated structures) or the vestibulocochlear nerve (cranial nerve VIII). SNHL accounts for about 90% of rep ...
and conductive), inherited in an autosomal dominant manner.
**
Crouzon syndrome
Crouzon syndrome is an autosomal dominant genetic disorder known as a branchial arch syndrome. Specifically, this syndrome affects the first branchial (or pharyngeal) arch, which is the precursor of the maxilla and mandible. Since the branchial ...
, characterised by bilateral atresia of the external auditory canal, inherited in an
autosomal dominant
In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and t ...
manner.
Surgery
Usually, malformations are treated with surgery, although artificial prostheses are also sometimes used.
*Preauricular fistulas are generally not treated unless chronically inflamed.
*Cosmetic defects without functional impairment are generally repaired after ages 6–7.
If malformations are accompanied by hearing loss amenable to correction, then the early use of
hearing aid
A hearing aid is a device designed to improve hearing by making sound audible to a person with hearing loss. Hearing aids are classified as medical devices in most countries, and regulated by the respective regulations. Small audio amplifiers s ...
s may prevent complete hearing loss.
Additional images
File:Gray907.png, External and middle ear, opened from the front. Right side.
See also
*
Ear
*
Inner ear
The inner ear (internal ear, auris interna) is the innermost part of the vertebrate ear. In vertebrates, the inner ear is mainly responsible for sound detection and balance. In mammals, it consists of the bony labyrinth, a hollow cavity in th ...
*
Middle ear
The middle ear is the portion of the ear medial to the eardrum, and distal to the oval window of the cochlea (of the inner ear).
The mammalian middle ear contains three ossicles, which transfer the vibrations of the eardrum into waves in the ...
*
Ear instillation
Ear instillation is the process of introducing otic medication or other liquids into the ear canal. Proper care is needed in delivering such liquids.
Indications for ear instillation
* patients with otitis media
* patients with otitis externa
* ...
*
Ear drop
Ear drops are a form of topical medication for the ears used to treat infection, inflammation, impacted ear wax and local anesthesia. They are commonly used for short-term treatment and can be purchased with or without a prescription. Before u ...
References
{{DEFAULTSORT:Outer Ear
Auditory system
Ear