Outer part of ear
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
.
[1]
It gathers sound energy and focuses it on the eardrum (
tympanic membrane
).
Structure
[
edit
]
Auricle
[
edit
]
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
, covered with integument, and connected to the surrounding parts by ligaments and muscles; and to the commencement of the
ear canal
by fibrous tissue. Many
mammals
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.
[2]
Ear canal
[
edit
]
From the pinna, the
sound waves
move into the
ear canal
(also known as the
external acoustic meatus
) a simple tube running through to the
middle ear
. 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.
[
citation needed
]
Auricular muscles
[
edit
]
Intrinsic muscles
[
edit
]
The
intrinsic auricular muscles
are:
- The
helicis major
is a narrow vertical band situated upon the anterior margin of the
helix
. 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
, covering the
crus helicis
.
- The
tragicus
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
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
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.
The intrinsic muscles contribute to the topography of the auricle, while also function as a sphincter of the external auditory meatus. It has been suggested that during prenatal development in the womb, these muscles exert forces on the cartilage which in turn affects the shaping of the ear.
[3]
Extrinsic muscles
[
edit
]
The
extrinsic auricular muscles
are the three
muscles
surrounding the
auricula
or outer ear:
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. The superior auricular muscle also acts as a stabilizer of the
occipitofrontalis muscle
and as a weak brow lifter.
[4]
The presence of auriculomotor activity in the posterior auricular muscle causes the muscle to contract and cause the pinna to be pulled backwards and flatten when exposed to sudden, surprising sounds.
[5]
Function
[
edit
]
| This section
needs expansion
. You can help by
adding to it
.
(
December 2013
)
|
One consequence of the configuration of the outer ear is selectively to boost the
sound pressure
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.
[6]
Clinical significance
[
edit
]
Malformations of the external ear can be a consequence of
hereditary disease
, or exposure to environmental factors such as
radiation
,
infection
. Such defects include:
- A
preauricular fistula
, which is a long narrow tube, usually near the
tragus
. This can be inherited as an
autosomal recessive
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
of the external auditory meatus
or
aplasia
of the pinna,
- Genetic
syndromes
, 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
manner.
- Goldenhar syndrome
, a combination of developmental abnormalities affecting the ears, eyes, bones of the skull, and vertebrae, inherited in an
autosomal dominant
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
and conductive), inherited in an autosomal dominant manner.
- Crouzon syndrome
, characterised by bilateral atresia of the external auditory canal, inherited in an
autosomal dominant
manner.
Surgery
[
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]
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 aids
may prevent complete hearing loss.
Additional images
[
edit
]
References
[
edit
]
This article incorporates text in the
public domain
from
page 1033
of the 20th edition of
Gray's Anatomy
(1918)
- ^
nyu.edu/classes/bello/FMT_files/2_hearing.pdf "Hearing" by Juan P Bello
- ^
"Why Can Some People Wiggle Their Ears?"
.
Live Science
. 30 March 2012.
- ^
Liugan, Mikee; Zhang, Ming; Cakmak, Yusuf Ozgur (2018).
"Neuroprosthetics for Auricular Muscles: Neural Networks and Clinical Aspects"
.
Frontiers in Neurology
.
8
: 752.
doi
:
10.3389/fneur.2017.00752
.
ISSN
1664-2295
.
PMC
5775970
.
PMID
29387041
.
- ^
Chon, Brian H.; Blandford, Alex D.; Hwang, Catherine J.; Petkovsek, Daniel; Zheng, Andrew; Zhao, Carrie; Cao, Jessica; Grissom, Nick; Perry, Julian D. (February 2021).
"Dimensions, Function and Applications of the Auricular Muscle in Facial Plastic Surgery"
.
Aesthetic Plastic Surgery
.
45
(1): 309?314.
doi
:
10.1007/s00266-020-02045-x
.
ISSN
1432-5241
.
PMID
33258010
.
S2CID
227236615
.
- ^
Strauss, Daniel J; Corona-Strauss, Farah I; Schroeer, Andreas; Flotho, Philipp; Hannemann, Ronny; Hackley, Steven A (2020-07-03). Groh, Jennifer M; Shinn-Cunningham, Barbara G; Verhulst, Sarah; Shera, Christopher; Corneil, Brian D (eds.).
"Vestigial auriculomotor activity indicates the direction of auditory attention in humans"
.
eLife
.
9
: e54536.
doi
:
10.7554/eLife.54536
.
ISSN
2050-084X
.
PMC
7334025
.
PMID
32618268
.
- ^
Purves, Dale, George J. Augustine, David Fitzpatrick, William C. Hall, Anthony-Samuel LaMantia, James O. McNamara, and Leonard E. White (2008). "Chapter 13".
Neuroscience. 4th ed
. Sinauer Associates. p. 317.
ISBN
978-0-87893-697-7
.
{{
cite book
}}
: CS1 maint: multiple names: authors list (
link
)
External links
[
edit
]
Media related to
Outer ear
at Wikimedia Commons