The outer ear, external ear, or auris externa is the external part of the

ear An ear is the organ that enables hearing and, in mammals, body balance using the vestibular system. In mammals, the ear is usually described as having three parts—the outer ear, the middle ear and the inner ear. The outer ear consists of ...

, 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 to the eardrum and is about in length and in diameter. Struc ...

. 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 air ...

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 audito ...

, covered with integument, and connected to the surrounding parts by ligaments and muscles; and to the commencement of the

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 or ...

s can move the pinna (with the

auriculares muscles 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. It gathers sound energy and focuses it on the eardrum (tympanic membrane). Structure Auricle Th ...

) 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

(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 The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...

to 12 kHz.

Muscles

Intrinsic muscles

The intrinsic muscles of the external ear are: * The

helicis major The helicis major (or large muscle of helix) is an intrinsic muscle of the outer ear. In human anatomy, it is the form of a narrow vertical band situated upon the anterior margin of the helix, at the point where the helix becomes transverse. It ...

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 helices, ...

. It arises below, from the

spina helicis At the front part of the auricula, where the helix bends upward, is a small projection of cartilage Cartilage is a resilient and smooth type of connective tissue. In tetrapods, it covers and protects the ends of long bones at the joints as ar ...

, and is inserted into the anterior border of the helix, just where it is about to curve backward. * The

helicis minor The Helicis minor (musculus helicis minor or smaller muscle of helix) is a small skeletal muscle. The helicis minor is an intrinsic muscle of the outer ear. The muscle runs obliques and covers the helical crus, part of the helix located just abo ...

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 short ...

, covering the

crus helicis Crus can refer to: *''Crus'', a subgenus of the fly genus '' Metopochetus'' *Crus (lower leg) *Crus, a plural of Cru (wine) *CRUs, an abbreviation of Civil Resettlement Units * Rektorenkonferenz der Schweizer Universitäten (CRUS; English: Recto ...

. * The tragicus is a short, flattened vertical band on the lateral surface of the tragus. Also known as the mini lobe. * The

antitragicus The antitragicus is an intrinsic muscle of the outer ear. In human anatomy, the antitragicus arises from the outer part of the antitragus, and is inserted into the cauda helicis (or tail of the helix) and antihelix. The function of the muscle i ...

arises from the outer part of the antitragus, and is inserted into the

cauda helicis In the lower part of the helix the cartilage is prolonged downward as a tail-like process, the cauda helicis; this is separated from the antihelix The antihelix (anthelix) is a part of the visible ear; the pinna. The antihelix is a curved promin ...

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 on the pinna. The antihelix divides above into two ''legs'' or crura; the ''crura antiheli ...

. * 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, ...

to the prominence corresponding with the

scapha The auricle or auricula is the visible part of the ear that is outside the head. It is also called the pinna (Latin for "wing" or "fin", plural pinnae), a term that is used more in zoology. Structure The diagram shows the shape and location of ...

. * 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 muscl ...

s surrounding the '' auricula'' or outer ear: *

anterior auricular muscle The anterior auricular muscle, the smallest of the three auricular muscles, is thin and fan-shaped, and its fibers are pale and indistinct. It arises from the lateral edge of the epicranial aponeurosis, and its fibers converge to be inserted into ...

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 supe ...

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 ba ...

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 hydrophone ...

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 A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosomal abnormality. Although polygenic disorders ...

, 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 dise ...

. Such defects include: *A

preauricular fistula Preauricular sinuses and preauricular cysts are two common congenital malformations. Each involves the external ear. The difference between them is that a cyst does not connect with the skin, but a sinus does. Frequency of preauricular sinus dif ...

, 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 and t ...

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 Aplasia (; from Greek ''a'', "not", "no" + ''plasis'', "formation") is a birth defect where an organ or tissue is wholly or largely absent. It is caused by a defect in a developmental process. Aplastic anemia is the failure of the body to produ ...

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 σύνδρομον, meaning "concurrence". When a syndrome is paired ...

s, which include: ** Konigsmark syndrome, characterised by small ears and atresia of the external auditory canal, causing

conductive hearing loss Conductive hearing loss (CHL) occurs when there is a problem transferring sound waves anywhere along the pathway through the outer ear, tympanic membrane (eardrum), or middle ear ( ossicles). If a conductive hearing loss occurs in conjunction wi ...

and inherited in an

manner. **

Goldenhar syndrome Goldenhar syndrome is a rare congenital defect characterized by incomplete development of the ear, nose, soft palate, lip and mandible on usually one side of the body. Common clinical manifestations include limbal dermoids, preauricular skin ta ...

, 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 Treacher Collins syndrome (TCS) is a genetic disorder characterized by deformities of the ears, eyes, cheekbones, and chin. The degree to which a person is affected, however, may vary from mild to severe. Complications may include breathing prob ...

, 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 r ...

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

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 su ...

s may prevent complete hearing loss.

Additional images

File:Gray907.png, External and middle ear, opened from the front. Right side.

References

{{DEFAULTSORT:Outer Ear Auditory system Ear