External auditory canal
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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 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 ...
and is about in length and in diameter.


Structure

The human ear canal is divided into two parts. The elastic cartilage part forms the outer third of the canal; its anterior and lower wall are cartilaginous, whereas its superior and back wall are fibrous. The cartilage is the continuation of the cartilage framework of pinna. The cartilaginous portion of the ear canal contains small hairs and specialized sweat glands, called apocrine glands, which produce cerumen (
ear wax An ear is the organ (anatomy), organ that enables hearing and, in mammals, Sense of balance, 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 in ...
). The bony part forms the inner two thirds. The bony part is much shorter in children and is only a ring (''annulus tympanicus'') in the newborn. The layer of epithelium encompassing the bony portion of the ear canal is much thinner and therefore, more sensitive in comparison to the cartilaginous portion. Size and shape of the canal vary among individuals. The canal is approximately long and in diameter.Faddis, B. T. (2008). "Structural and functional anatomy of the outer and middle ear". In W. Clark & K. Ohlemiller (Eds.), ''Anatomy and physiology of hearing for audiologists'' (pp. 93–108). Thomson Delmar Learning. It has a sigmoid form and runs from behind and above downward and forward. On the cross-section, it is of oval shape. These are important factors to consider when fitting
earplug An earplug is a device that is inserted in the ear canal to protect the user's ears from loud noises, intrusion of water, foreign bodies, dust or excessive wind. Since they reduce the sound volume, earplugs are often used to help prevent heari ...
s.


Disorders

Due to its relative exposure to the outside world, the ear canal is susceptible to diseases and other disorders. Some disorders include: *
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 ear canal *Cerumen impaction * Bone exposure, caused by the wearing away of skin in the canal *Auditory canal osteoma (bony outgrowths of the temporal bone) * Cholesteatoma *
Contact dermatitis Contact dermatitis is a type of acute or chronic inflammation of the skin caused by exposure to chemical or physical agents. Symptoms of contact dermatitis can include itchy or dry skin, a red rash, bumps, blisters, or swelling. These rashes are ...
of the ear canal * Fungal infection ( otomycosis) *
Ear mite Ear mites are mites that live in the ears of animals and humans. The most commonly seen species in veterinary medicine is '' Otodectes cynotis'' (Gk. ''oto''=ear, ''dectes''=biter, ''cynotis''=of the dog). This species, despite its name, is also ...
s in animals * Ear
myiasis Myiasis is the parasitic infestation of the body of a live animal by fly larvae (maggots) which grow inside the host while feeding on its tissue. Although flies are most commonly attracted to open wounds and urine- or feces-soaked fur, some spe ...
, an extremely rare infestation of maggots *Foreign body in ear *
Granuloma A granuloma is an aggregation of macrophages that forms in response to chronic inflammation. This occurs when the immune system attempts to isolate foreign substances that it is otherwise unable to eliminate. Such substances include infectious o ...
, a
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 ...
usually caused by tympanostomy tubes * Otitis externa (swimmer's ear), bacteria-caused inflammation of the ear canal *
Stenosis A stenosis (from Ancient Greek στενός, "narrow") is an abnormal narrowing in a blood vessel or other tubular organ or structure such as foramina and canals. It is also sometimes called a stricture (as in urethral stricture). ''Stricture'' ...
, a gradual closing of the canal


Earwax

Earwax, also known as cerumen, is a yellowish, waxy substance secreted in the ear canals. It plays an important role in the human ear canal, assisting in cleaning and lubrication, and also provides some protection from
bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...
,
fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately fr ...
, and
insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pa ...
s. Excess or impacted cerumen can press against the eardrum and/or occlude the external auditory canal and impair hearing, causing conductive hearing loss. If left untreated, cerumen impaction can also increase the risk of developing an infection within the ear canal.


Additional images

File:Gray187.png, Base of skull. Inferior surface. File:Gray189.png, Left infratemporal fossa. File:Gray907.png, External and middle ear, opened from the front. Right side. File:Gray908.png, Horizontal section through left ear; upper half of section. File:Slide1CAC.JPG, Lateral head anatomy detail. Facial nerve dissection.


See also

* List of specialized glands within the human integumentary system


References


External links


Veterans Health Administration web siteOtoscopy Tutorial w/ Images
* {{Authority control Auditory system Ear