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 lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is e ...

" or " fin", plural pinnae), a term that is used more in

zoology Zoology ()The pronunciation of zoology as is usually regarded as nonstandard, though it is not uncommon. is the branch of biology that studies the animal kingdom, including the structure, embryology, evolution, classification, habits, an ...

Structure

The diagram shows the shape and location of most of these components: * ''

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 ...

'' 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'' 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 * ''Fossa triangularis'' is the depression in the fork of the ''antihelix'' * Helix is the folded over outside edge of the ear * ''

Incisura anterior auris The intertragic notch is an anatomical feature of the ears of mammals. In humans, it is the space that separates the tragus from the antitragus in the outer ear. It is the point specified (although not by that name) in the U.S. Army’s regulatio ...

'', 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 Inflammation of the geniculate ganglion of the facial nerve is a late consequence of '' varicella zoster'' virus (VZV) known as Ramsay Hunt syndrome (RHS), commonly known as herpes zoster oticus. In regards with the frequency, less than 1% of va ...

). 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

trauma Trauma most often refers to: *Major trauma, in physical medicine, severe physical injury caused by an external source *Psychological trauma, a type of damage to the psyche that occurs as a result of a severely distressing event *Traumatic inju ...

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 , mottoeng = The Heights Yield to Endeavour , type = Public research university , established = 1862 – Hartley Institution1902 – Hartley University College1913 – Southampton University Coll ...

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 In physics, interference is a phenomenon in which two waves combine by adding their displacement together at every single point in space and time, to form a resultant wave of greater, lower, or the same amplitude. Constructive and destructi ...

, 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.

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, vertical sound localization, 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 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 organs, and tissues of the body. Thus, scarring is a ...

s, including keloids * cystPinna abnormalities and low-set ears.
MedlinePlus. * skin tag * sunburn,

frostbite Frostbite is a skin injury that occurs when exposed to extreme low temperatures, causing the freezing of the skin or other tissues, commonly affecting the fingers, toes, nose, ears, cheeks and chin areas. Most often, frostbite occurs in t ...

* pressure ulcer, often from a poorly fitting

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 ...

* anotia, absent pinna *

microtia Microtia is a congenital deformity where the auricle (external ear) is underdeveloped. A completely undeveloped pinna is referred to as anotia. Because microtia and anotia have the same origin, it can be referred to as microtia-anotia. Microti ...

, 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 Chondrodermatitis nodularis chronica helicis is a small, nodular, tender, chronic inflammatory lesion occurring on the helix of the ear, most often in men. it often presents as a benign painful erythematous nodule fixed to the cartilage of the h ...

(Winkler's nodule), a nodule initiated by solar damage *

actinic keratosis Actinic keratosis (AK), sometimes called solar keratosis or senile keratosis, is a pre-cancerous area of thick, scaly, or crusty skin.Freedberg, et al. (2003). ''Fitzpatrick's Dermatology in General Medicine''. (6th ed.). McGraw-Hill. . Actinic k ...

and cutaneous horn, premalignant lesions caused by solar damage * benign and malignant

neoplasm A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...

, including tumors, keratoacanthoma, carcinoma

In other species

Visible auricles are a common trait in mammals, particularly placental mammals and marsupials, but are poorly developed or absent in monotremes. Many marine mammals usually have either reduced auricles or no auricals 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 auricles in Spinolestes. External auricles are absent in other tetrapod groups such as reptiles, amphibians, and

birds Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...

Additional images

File:Ear with earring.jpg, Left human pinna 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

References

External links

drtbalu otolaryngology online
* {{Authority control Ear Auditory system