Ear

The hearing organ. There are three sections of the ear, according to the anatomy textbooks. They are the outer ear (the part we see along the sides of our head behind the temples), the middle ear, and the inner ear. But in terms of function, the ear has four parts: those three and the brain. Hearing thus involves all parts of the ear as well as the auditory cortex of the brain. The external ear helps concentrate the vibrations of air on the ear drum and make it vibrate. These vibrations are transmitted by a chain of little bones in the middle ear to the inner ear. There they stimulate the fibers of the auditory nerve to transmit impulses to the brain. The outer ear looks complicated but it is the simplest part of the ear. It consists of the pinna or auricle (the visible projecting portion of the ear), the external acoustic meatus (the outside opening to the ear canal), and the external ear canal that leads to the ear drum. In sum, there is the pinna, the meatus and the canal. That's all. And the external ear has only to concentrate air vibrations on the ear drum and make the drum vibrate. The middle ear consists of the ear drum (the tympanum or tympanic membrane) and, beyond it, a cavity. This cavity is connected via a canal (the Eustachian tube) to the pharynx (the nasopharynx). The Eustachian tube permits the gas pressure in the middle ear cavity to adjust to external air pressure (so, as you're descending in a plane, it's the Eustachian tube that opens when your ears "open").) The middle ear cavity also contains a chain of 3 little bones (ossicles) that connect the ear drum to the internal ear. The ossicles are named (not the Nina, the Pinta and the Santa Maria but) the malleus, incus, and stapes. In sum, the middle ear communicates with the pharynx, equilibrates with external pressure and transmits the ear drum vibrations to the inner ear. The internal ear is highly complex. The essential component of the inner ear for hearing is the membranous labyrinth where the fibers of the auditory nerve (the nerve connecting the ear to the brain) end. The membranous labyrinth is a system of communicating sacs and ducts (tubes) filled with fluid (the endolymph). The membranous labyrinth is lodged within a cavity called the bony labyrinth. At some points the membranous labyrinth is attached to the bony labyrinth and at other points the membranous labyrinth is suspended in a fluid (the perilymph) within the bony labyrinth. The bony labyrinth has three parts: a central cavity (the vestibule), semicircular canals (which open into the vestibule) and the cochlea (a snail-shaped spiral tube). The membranous labyrinth also has a vestibule which consists of two sacs (called the utriculus and sacculus) connected by a narrow tube. The utriculus, the larger of the two sacs, is the principal organ of the vestibular system (which informs us about the position and movement of the head). The smaller of the two sacs, the sacculus (literally, the little sac) is connected with a membranous tube in the cochlea containing the organ of Corti. It is in the organ of Corti that are situated the hair cells, the special sensory receptors for hearing.

* * *

The organ of hearing : composed of the external e., which includes the auricle and the external acoustic, or auditory, meatus; the middle e., or the tympanic cavity with its ossicles; and the internal e. or inner e., or labyrinth, which includes the semicircular canals, vestibule, and cochlea. SEE ALSO: auricle. SYN: auris [TA]. [A.S. eáre]

- Aztec e. an auricle with the lobule absent.

- bat e. SYN: lop-e..

- bladder e. protrusion of a portion of the bladder into proximal inguinal canal; often seen in pediatric VCUGs and rarely of clinical significance.

- Blainville ears asymmetry in size or shape of the auricles.

- boxer's e. SYN: cauliflower e..

- Cagot e. (ka-go′) an auricle having no lobulus. [a people in the Pyrenees among whom physical stigmata are common]

- cauliflower e. thickening and induration of the e. with distortion of contours following extravasation of blood within its tissues. SYN: boxer's e..

- darwinian e. an auricle in which the upper border is not rolled over to form the helix, but projects upward as a flat, sharp edge.

- dog e. redundant corner of skin, usually the result of mismatch of skin edges in a wound closure, leaving an excessive hump or triangular bit of tissue.

- external e. SYN: auris externa. SEE ALSO: auricle, external acoustic meatus, pinna.

- glue e. middle e. inflammation with thick mucoid effusion caused by long-standing eustachian tube obstruction.

- internal e. SYN: auris interna. SEE ALSO: labyrinth.

- lop e. SYN: outstanding e.. See lop-e..

- middle e. SYN: auris media. SEE ALSO: tympanic cavity.

- Morel e. a large, misshapen, outstanding auricle, with obliterated grooves and thinned edges.

- Mozart e. a deformity of the pinna where the two crura of the antihelix and the crus of the helix are fused, giving a bulging appearance of the superior part of the pinna. [Wolfgang Amadeus Mozart, 1756–1791, composer, said to have had this deformity]

- outstanding e. excessive protrusion of the e. from the head, usually due to failure of the antihelical fold to develop. SYN: lop e., protruding e..

- protruding e. SYN: outstanding e..

- scroll e. a deformity of the external e. in which the pinna is rolled forward.

- Stahl e. a deformed external e., in which the fossa ovalis and upper portion of the scaphoid fossa are covered by the helix; once regarded as a stigma of degenerate constitution.

- swimmer's e. SYN: otitis externa.

- telephone e. noise-induced hearing loss due to exposure to static over telephones.

- Wildermuth e. an e. in which the helix is turned backward and the anthelix is prominent.

* * *

European Association of Radiology

* * *

ear 'i(ə)r n

1) the characteristic vertebrate organ of hearing and equilibrium consisting in the typical mammal of a sound-collecting outer ear separated by the tympanic membrane from a sound-transmitting middle ear that in turn is separated from a sensory inner ear by membranous fenestrae

2 a) the external ear of humans and most mammals

b) a human earlobe <had her \ears pierced>

3 a) the sense or act of hearing

b) acuity of hearing

* * *

n.

the sense organ concerned with hearing and balance. Sound waves, transmitted from the outside into the external auditory meatus, cause the eardrum (tympanic membrane) to vibrate. The small bones (ossicles) of the middle ear - the malleus, incus, and stapes - transmit the sound vibrations to the fenestra ovalis, which leads to the inner ear (see labyrinth). Inside the cochlea the sound vibrations are converted into nerve impulses. Vibrations emerging from the cochlea could cause pressure to build up inside the ear, but this is released through the Eustachian tube. The semicircular canals, saccule, and utricle - also in the inner ear - are all concerned with balance.

* * *

expired air resuscitation.