Ear

The ear is the body which is used to collect the its and is responsible for the direction of the Ouïe. The word can refer to the whole system which carries out the collection and the comprehension of the sounds, or to the external part only.

The Mammalian ear of the S

Majority of the mammals, whose human being, have two ears, one on each side of the head. Their main components are:

  • auditory House

  • Canal
  • Tympanum
  • lenticular Clamp
  • Os
  • Hammer
  • oval Anvil
  • Window
  • round Window
  • Eustachian tube
  • Scala tympani
  • Scala vestibuli
  • Cochlea
  • nervous Fiber
  • semicircular Channels

These components are divided into three distinct zones.

The Outer ear

The outer ear includes/understands two segments: the house and the external auditory canal
  • the house is a blade folded on itself in various directions, ovalaire at large higher end by having as a whole the shape of a house of ear trumpet. The house has a skeleton made of elastic cartilage enabling him to take again its normal position. On this level there does not exist subcutaneous cellular fabric. The lower part is represented by the ear lobe of which the central part fat, is innervée little and richly vascularized.
  • the external auditory canal with the shape of an acoustic horn which decreases by diameter as one approaches towards the bottom i.e. the tympanum: the external two-thirds have a cartilagineux skeleton and the internal third has an osseous skeleton in the temporal membrane (air bone). Its internal part is covered of skin which contains many pores with glands sébacés and glands sudoripares apocrines: cérumineuses glands which manufacture of a liquid proteinic and glucolipidic, pigmented and sticking, cerumen.

The Middle ear

It includes/understands the tympanum ( tympanum ), as well as the ossicles (the “chain ossiculaire”), four very small Os. They are called respectively the hammer ( maleus ), the anvil ( incus ), the lenticular Os (which is the smallest bone of the human body) and the clamp ( pillars ). These names come from their characteristic forms. The hammer and the anvil form a not very flexible articulation called block incudo-maléaire.

The sounds are the result of vibrations of the air in the auditory canal which cause to make vibrate the tympanum. These vibrations will be then transmitted to the ossicles then with the internal ear via the oval window.

The design which currently dominates over the propagation of the vibrations in the middle ear is that of Khana and Tonndorf, elaborate in 1972: schematically, the lines of the concentric zones of Iso-amplitude of certain frequencies are parallel to the handle of the hammer, with, for the membrane of the tympanum, the zones of vibration fuller than for this handle.

Since the middle ear is hollow, an environment of high pressure (as water) would pose the risk to burst the tympanum. To mitigate this risk is the function of the Eustachian tubes. Descendants évolutionnaires of respiratory hearing of the Poisson S, these horns connect the middle ear to the nasal fossae in order to decompress the middle ears.

The Internal ear

She contains not only the body of hearing, the Cochlée or snail ( cochlea ), but also the hall , body of balance, person in charge of the perception of the angular position of the head and her acceleration. The movements of the clamp are transmitted to the Cochlée via the oval window and the hall.

The Cochlée is a hollow body filled with a liquid called endolymphe ( endolympha ). It is papered of ciliées cells - capped sensory cells of filamentous structures, the stéréocils ( stereocilia ), grouped in a free tuft ciliaire to vibrate. These cells are laid out along a membrane (the membrane basilaire ) which comes partitionner the Cochlée in two rooms. The whole of the ciliées cells and the membranes which are assistant for them constitutes the body of Corti .

The membrane basilaire and the ciliées cells which it door are put moving by the vibrations transmitted through the median ear. Along the Cochlea, each cell answers a certain frequency preferentially, to make it possible the brain to differentiate the height from the sounds. Thus, the ciliées cells closest to the base of the cochlea (oval window, with more close to the median ear) answer the acute ones preferentially. Those located in its apex (last tower of the cochlea) answer the low frequencies.

In fact the ciliées cells make the mecanoelectric Transduction: they transform a movement of their tuft ciliaire into nervous Signal by the auditive Nerf, which will be interpreted by the Cerveau like a its of the tonal Height corresponding to the excited cell.

The vestibular apparatus constitutes of three semicircular channels , orthogonally arranged on the three planes. They are filled of same the endolymphe as the cochlea. When the ear is subjected to a movement, the inertia of this liquid makes this movement detectable by ciliées cells, completely similar to those of the Cochlée. The provision of the three channels in three orthogonal plans makes it possible to detect the angular position of the head in all the possible directions.

Diseases of the ear and hearing

See too

Internal bonds

ear|ear

External bonds

  • Walk around the cochlea

Fiu-vro: Kõrv Simple: Ear Zh-min-nan: Hīⁿ

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