The structure of the ear
The ear consists of three parts: the outer, middle and inner.
The outer ear includes the pinna, which collects and directs sound waves, and the external auditory canal, through which they pass to the eardrum, causing it to move.
The middle ear consists of the eardrum andthree small bones (hammer, anvil and stirrup). United together, they form with the eardrum moving mechanical system of sound vibrations. The air pressure in the middle ear cavity through the atmospheric auditory or eustachian, tube that connects it with the nasal cavity. In children this shorter pipe and direct than in adults, which facilitates the penetration of the infection into the nasal cavity of the middle ear.
The concept of the inner ear (labyrinth) consists of threestructure: the snail, and the threshold of the semicircular canals. By hearing the analyzer has a direct bearing on the cochlea (it contains the sound-machine), and the threshold and the semicircular canals of the vestibular analyzer to include regulating the balance, body movement in space, coordination of movements and so forth.
The inner ear (cochlea) filled with liquid,which converts vibrations transmitted from the middle ear into nerve impulses. That is, the membrane oscillations driven middle ear bone, the signal is amplified and transmitted from the bones into the cochlea, where the liquid is excited oscillation hairs receptors immersed in this liquid. These signals are received by the auditory nerve to the brain.
Diseases of the ear
Professional ear diseases develop for the following reasons:
- prolonged exposure to sudden noises, sounds and vibrations
- sharp differences of atmospheric pressure
- toxic effects of certain chemicals used in the manufacturing process.
Prolonged exposure to noise and sounds
Prolonged exposure to noise and soundsexcessive force causes the inner ear injury. An example of such effects can be sharp high-pitched whistle of the locomotive, and the noise of a jet engine, giving 150-160 dB, which exceeds the threshold of pain sensitivity. The trauma causes bleeding in the cochlea, the displacement and the swelling spiral organ cells (located in the inner ear, sound vibrations directly voprinimaet).
In modern production facilities are more commonchronic acoustic (auditory) injury - to heavy industrial plants, machinery for weaving mills. Prolonged exposure to noise in the intensity of its 70 to 100 dB, and shaking cause hearing loss analyzer. The degree of hearing loss depends on the nature of the noise and the duration of work in hazardous environments. The noise transmitted through the air, first cause hearing loss at high frequencies, and then to low.
Production processes are accompanied byvibration, reduce the perception of low frequency sounds. Prolonged exposure to vibrations propagating through bone conduction, causes devastating changes in the nerve cells of the ear and vestibular apparatus. The impact of noise on the central nervous system is manifested in the form of fatigue, reduced performance, the development of neuroses.
Sudden changes in atmospheric pressure
Sudden atmospheric pressure causeear damage, called barotrauma. Meets is a professional disease of divers and pilots, when working in the caissons. During normal patency of the auditory tube (ear, and connects the nasopharynx, and serves to equalize the pressure in both cavities) usually occurs alignment changing atmospheric pressure. Violation of the auditory tube patency at differences of pressure leads to a sharp protrusion or indentation of the tympanic membrane up to its rupture. The rapid reduction of pressure in the middle ear, leading to dilation of blood vessels, transudate effusion, hemorrhage development. The rapid increase in atmospheric pressure may cause severe pain.
If barotrauma oto- picture can be of different nature:
- bleeding in the tympanic cavity without rupture of the tympanic membrane appears as a dark blue translucence;
- perforation of the large size and yellow color of the tympanic cavity mucosa observed at rupture of the tympanic membrane;
- complete destruction of the tympanic membrane under intense trauma.
Hearing loss occurs by sound conduction disorders. In severe injuries pressure is transmitted to the inner ear and hearing loss has a mixed character.
Assistance with barotrauma isPrevention of infection in the middle ear. This requires the introduction of the external auditory canal of a sterile cotton ball and providing specialist advice. In the case of secondary infection is the treatment of purulent otitis media. Small gaps eardrum zarubtsovyvayutsya quickly, bleeding in the tympanic cavity dissolves more durable.
The toxic effects of chemical substances
The toxic effects of chemical substancescause inner ear damage. Toxic effect on the ear have a lead and its compounds, mercury, arsenic and benzene. There are cases of lesions of hearing when working with carbon monoxide. All of these substances can cause hearing loss and deafness.