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.
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 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, an extremely rare infestation of maggots
*Foreign body in ear
*
Granuloma, 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