Ear canal
Encyclopedia
The ear canal , is a tube running from the outer ear
Outer ear
The outer ear is the external portion of the ear, which consists of the pinna, concha, and external auditory meatus. It gathers sound energy and focuses it on the eardrum . One consequence of the configuration of the external ear is to selectively boost the sound pressure 30- to 100-fold for...

 to the middle ear
Middle ear
The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the cochlea. The mammalian middle ear contains three ossicles, which couple vibration of the eardrum into waves in the fluid and membranes of the inner ear. The hollow space of the middle ear has...

. The human ear canal extends from the pinna to the eardrum
Eardrum
The eardrum, or tympanic membrane, is a thin membrane that separates the external ear from the middle ear in humans and other tetrapods. Its function is to transmit sound from the air to the ossicles inside the middle ear. The malleus bone bridges the gap between the eardrum and the other ossicles...

 and is about 35 mm in length and 5 to 10 mm in diameter.

Structure

The human ear canal is divided into two parts. The fibrocartilaginous 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 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.

Size and shape of the canal vary among individuals. The canal is approximately 35 mm long and 5 to 10 mm in diameter. 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
Earplug
An earplug is a device that is meant to be inserted in the ear canal to protect the wearer's ears from loud noises or the intrusion of water, foreign bodies, dust or excessive wind.-Protection from water:...

s.

Disorders

The ear canal, because of its relative exposure to the outside world, is a common victim of diseases and other disorders. Some disorders include:
  • Atresia
    Atresia
    Atresia is a condition in which a body orifice or passage in the body is abnormally closed or absent.Examples of atresia include:* Imperforate anus - malformation of the opening between the rectum and anus....

     of the ear canal
  • Otitis externa
    Otitis externa
    Otitis externa is an inflammation of the outer ear and ear canal. Along with otitis media, external otitis is one of the two human conditions commonly called "earache". It also occurs in many other species. Inflammation of the skin of the ear canal is the essence of this disorder...

     (swimmer's ear), bacteria-caused inflammation of the ear canal
  • Contact dermatitis
    Contact dermatitis
    Contact dermatitis is a term for a skin reaction resulting from exposure to allergens or irritants . Phototoxic dermatitis occurs when the allergen or irritant is activated by sunlight....

     of the ear canal
  • Ear fungus
  • Ear myiasis
    Myiasis
    Myiasis is a general term for infection by parasitic fly larvae feeding on the host's necrotic or living tissue. Colloquialisms for myiasis include flystrike, blowfly strike, and fly-blown. In Greek, "myia" means fly....

    , an extremely rare infestation of maggots
  • Bone exposure, caused by the wearing away of skin in the canal
  • Granuloma
    Granuloma
    Granuloma is a medical term for a tiny collection of immune cells known as macrophages. Granulomas form when the immune system attempts to wall off substances that it perceives as foreign but is unable to eliminate. Such substances include infectious organisms such as bacteria and fungi as well as...

    , a scar
    Scar
    Scars are areas of fibrous tissue that replace normal skin after injury. A scar results from the biological process of wound repair in the skin and other tissues of the body. Thus, scarring is a natural part of the healing process. With the exception of very minor lesions, every wound results in...

     usually caused by tympanostomy tube
    Tympanostomy tube
    A tympanostomy tube is a small tube inserted into the eardrum in order to keep the middle ear aerated for a prolonged period of time, and to prevent the accumulation of mucus in the middle ear. The operation to insert the tube involves a myringotomy...

    s
  • Stenosis
    Stenosis
    A stenosis is an abnormal narrowing in a blood vessel or other tubular organ or structure.It is also sometimes called a stricture ....

    , a gradual closing of the canal
  • Foreign body in ear
  • Cholesteatoma
    Cholesteatoma
    Cholesteatoma is a destructive and expanding growth consisting of keratinizing squamous epithelium in the middle ear and/or mastoid process.-Signs and symptoms:...

  • Ear mite
    Ear mite
    Ear mites are mites that live in the ears of animals. The most commonly seen species is Otodectes cynotis .-Contagion:...

    s in animals.

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, fungi
Fungus
A fungus is a member of a large 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, Fungi, which is separate from plants, animals, and bacteria...

, and insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s. Excess or impacted cerumen can press against the eardrum and/or occlude the external auditory canal and impair hearing.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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