pinna (anatomy)
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The auricle or auricula is the visible part of the ear that is outside the head. It is also called the pinna (
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for '
wing A wing is a type of fin that produces both Lift (force), lift and drag while moving through air. Wings are defined by two shape characteristics, an airfoil section and a planform (aeronautics), planform. Wing efficiency is expressed as lift-to-d ...
' or ' fin', : pinnae), a term that is used more in
zoology Zoology ( , ) is the scientific study of animals. Its studies include the anatomy, structure, embryology, Biological classification, classification, Ethology, habits, and distribution of all animals, both living and extinction, extinct, and ...
.


Structure

The diagram shows the shape and location of most of these components: * '' antihelix'' forms a 'Y' shape where the upper parts are: ** ''Superior crus'' (to the left of the ''fossa triangularis'' in the diagram) ** ''Inferior crus'' (to the right of the ''fossa triangularis'' in the diagram) * ''
Antitragus The antitragus is a feature of mammalian ear anatomy. In humans, it is a small Tubercle (anatomy)#Ears, tubercle on the visible part of the ear, the Auricle (anatomy), auricle. The antitragus is located just above the earlobe and points anatomical ...
'' is below the ''tragus'' * ''Aperture'' is the entrance to the ear canal * ''Auricular sulcus'' is the depression behind the ear next to the head * ''Concha'' is the hollow next to the ear canal * Conchal angle is the angle that the back of the ''concha'' makes with the side of the head * ''Crus'' of the helix is just above the ''tragus'' * ''Cymba conchae'' is the narrowest end of the ''concha'' * External auditory meatus is 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 auricle to the eardrum and is about in length and in diameter. S ...
* ''Fossa triangularis'' is the depression in the fork of the ''antihelix'' * Helix is the folded over outside edge of the ear * '' Incisura anterior auris'', or intertragic incisure, or intertragal notch, is the space between the ''tragus'' and ''antitragus'' * Lobe (lobule) * ''Scapha'', the depression or groove between the helix and the anthelix * Tragus


Development

The developing auricle is first noticeable around the sixth week of gestation in the human fetus, developing from the auricular hillocks, which are derived from the first and second pharyngeal arches. These hillocks develop into the folds of the auricle and gradually shift upwards and backwards to their final position on the head. En route accessory auricles (also known as preauricular tags) may be left behind. The first three hillocks are derived from the 1st branchial arch and form the tragus, crus of the helix, and helix, respectively. Cutaneous sensation to these areas is via the trigeminal nerve, the attendant nerve of the 1st branchial arch. The final three hillocks are derived from the second branchial arch and form the antihelix, antitragus, and lobule, respectively. These portions of the ear are supplied by the cervical plexus and a small portion by the facial nerve. This explains why vesicles are classically seen on the auricle in herpes infections of the facial nerve ( Ramsay Hunt syndrome type II). The auricle's functions are to collect sound and transform it into directional and other information. The auricle collects sound and, like a funnel, amplifies the sound and directs it to the auditory canal. The filtering effect of the human pinnae preferentially selects sounds in the frequency range of human speech.


Amplification and modulation

Amplification of sound by the pinna, tympanic membrane and middle ear causes an increase in level of about 10 to 15 dB in a frequency range of 1.5 kHz to 7 kHz. This amplification is an important factor in
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 the ...
trauma resulting from elevated sound levels. Non-electrical hearing apparatuses which were designed to protect hearing (particularly that of musicians and others who work in loud environments) which fit snugly in the concha have been studied by the Institute of Sound and Vibration Research (ISVR) at the
University of Southampton The University of Southampton (abbreviated as ''Soton'' in post-nominal letters) is a public university, public research university in Southampton, England. Southampton is a founding member of the Russell Group of research-intensive universit ...
in the U.K.


Notch of pinna

Due to its anatomy, the pinna largely eliminates a small segment of the frequency spectrum; this band is called the '. The pinna works differently for low and high frequency sounds. For low frequencies, it behaves similarly to a reflector dish, directing sounds toward the ear canal. For high frequencies, however, its value is thought to be more sophisticated. While some of the sounds that enter the ear travel directly to the canal, others reflect off the contours of the pinna first: these enter the ear canal after a very slight delay. This delay causes phase cancellation, virtually eliminating the frequency component whose wave period is twice the delay period. Neighboring frequencies also drop significantly. In the affected frequency band – the pinna notch – the pinna creates a band-stop or notch filtering effect. This filter typically affects sounds around 10 kHz, though it can affect any frequencies from 6 – 16 kHz. It also is directionally dependent, affecting sounds coming from above more than those coming from straight ahead. This aids in vertical
sound localization Sound localization is a listener's ability to identify the location or origin of a detected sound in direction and distance. The sound localization mechanisms of the mammalian auditory system have been extensively studied. The auditory system u ...
.


Functions

In animals, the function of the ''pinna'' is to collect sound, and perform spectral transformations to incoming sounds which enable the process of vertical localization to take place. It collects sound by acting as a funnel, amplifying the sound and directing it to the auditory canal. While reflecting from the pinna, sound also goes through a filtering process, as well as frequency dependent amplitude modulation which adds directional information to the sound (see
sound localization Sound localization is a listener's ability to identify the location or origin of a detected sound in direction and distance. The sound localization mechanisms of the mammalian auditory system have been extensively studied. The auditory system u ...
, head-related transfer function, pinna notch). In various species, the pinna can also signal mood and radiate heat.


Clinical significance

There are various visible ear abnormalities: * traumatic injury * infection * wart, mole, birthmark *
scar A scar (or scar tissue) is an area of fibrosis, fibrous tissue that replaces normal skin after an injury. Scars result from the biological process of wound repair in the skin, as well as in other Organ (anatomy), organs, and biological tissue, t ...
s, including keloids * cystPinna abnormalities and low-set ears.
MedlinePlus.
*
skin tag A skin tag, or acrochordon (: acrochorda), is a small benign tumor that forms primarily in areas where the Human skin, skin forms creases (or rubs together), such as the neck, armpit and groin. They may also occur on the face, usually on the ey ...
* sunburn, frostbite *
pressure ulcer Pressure ulcers, also known as pressure sores, bed sores or pressure injuries, are localised ulcer (dermatology), damage to the skin and/or underlying tissue that usually occur over a Bone, bony prominence as a result of usually long-term pres ...
, often from a poorly fitting hearing aid * anotia, absent pinna * microtia, underdeveloped pinna * cryptotia, a pinna covered beneath the skin of the scalpEar Deformities.
Division of Plastic and Reconstructive Surgery. University of North Carolina at Chapel Hill School of Medicine.
* Stahl's deformity, pointed pinna due to an extra fold of cartilage * cupped or constricted ear deformity, a hooded superior helix * preauricular pitNeonatal Dermatology: Ear Anomalies.
Auckland District Health Board.
* preauricular tag * Darwin's tubercle, protuberance on the anterior helixHawke, M. (2003
Chapter 1: Diseases of the Pinna.
''Ear Disease: A Clinical Guide''. Hamilton, Ontario. Decker DTC.
* hypertrichosis, including hypertrichosis lanuginosa acquisita, a hairy pinna * cauliflower ear, post-traumatic cartilage deformity * tophus, nodule on the pinna related to gout * chondrodermatitis nodularis chronica helicis (Winkler's nodule), a nodule initiated by solar damage * actinic keratosis and cutaneous horn, premalignant lesions caused by solar damage * benign and malignant neoplasm, including tumors, keratoacanthoma, carcinoma


In other species

Visible pinnae are a common trait in
theria Theria ( or ; ) is a scientific classification, subclass of mammals amongst the Theriiformes. Theria includes the eutherians (including the Placentalia, placental mammals) and the metatherians (including the marsupials) but excludes the egg-lay ...
n mammals ( placentals and marsupials), but are poorly developed or absent in monotremes. Marine mammals usually have either reduced pinnae or no pinnae due to sound travelling differently in water than in air, as well as the fact that auricles would potentially slow them down in the water. Skin impressions show large, mouse-like pinnae in '' Spinolestes''. External pinnae are absent in other tetrapod groups such as reptiles,
amphibians Amphibians are ectothermic, anamniote, anamniotic, tetrapod, four-limbed vertebrate animals that constitute the class (biology), class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all Tetrapod, tetrapods, but excl ...
, and
birds Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...
.


Additional images

File:Ear with earring.jpg, Left human auricle File:Slide2COR.JPG, External ear. Right auricle. Lateral view. File:Slide3COR.JPG, External ear. Right auricle. Lateral view. File:Slide4COR.JPG, External ear. Right auricle. Lateral view. File:Large, rounded, well-defined male ear.jpg, Male right auricle


See also

* Earrings for pierced ears * Auriculotherapy


References


External links


drtbalu otolaryngology online
* {{Authority control Ear Auditory system