Hearing organs allow you to perceive the variety of sounds of the outside world, to recognize their nature and location. Thanks to the ability to hear, a person gains the ability to speak. The hearing organ is a complex, finely tuned system of three departments connected in series.
Outer ear
The first section is the auricle - a complex form of the cartilaginous plate, covered on both sides by the skin, and the external auditory meatus.
The main function of the auricle is the adoption of acoustic air vibrations. From the hole in the auricle, the external auditory meatus begins - a tube 27 - 35 mm long that goes deep into the temporal bone of the skull. In the skin lining the ear canal, there are sulfur glands, the secret of which prevents the penetration of infection into the organ of hearing. The eardrum, a thin but strong membrane, separates the outer ear from the second section of the hearing organ, middle ear.
Middle ear
In the deepening of the temporal bone is the tympanic cavity, which makes up the main part of the middle ear. The auditory (Eustachian) tube is the connecting link between the middle ear and the nasopharynx. During swallowing movements, the Eustachian tube opens and allows air to penetrate into the middle ear, which balances the pressure in the tympanic cavity and the external auditory canal.
In the middle ear, there are miniature auditory ossicles movably interconnected, a complex mechanism for transmitting acoustic vibrations coming from the external auditory canal to the auditory cells of the inner ear. The first bone is a malleus, with a long end attached to the eardrum. The second is an anvil connected to the third miniature bone, a stirrup. The stirrup is adjacent to the oval window from which the inner ear begins. The bones, which includes the organ of hearing, are very small. For example, the mass of the stapes is only 2.5 mg.
Inner ear
The third section of the hearing organ is represented by the vestibule (miniature bone chamber), semicircular canals and a special formation - a thin-walled bone tube twisted into a spiral.
This part of the auditory analyzer, reminiscent of the shape of a grape snail, is called the auditory snail.
The hearing organ has important anatomical formations, which allows you to maintain balance and evaluate the position of the body in space. This is the vestibule and semicircular canals, filled with liquid and lined with very sensitive cells from the inside. When a person changes the position of the body, there is a displacement of fluid in the channels. Receptors record fluid displacement and send a signal about this event to the brain. So the organ of hearing and balance allows the brain to learn about the movements of our body.
The membrane inside the cochlea consists of about 25 thousand of the thinnest fibers of various lengths, each of which responds to sounds of a certain frequency and excites the ends of the auditory nerve. Nerve stimulation is first transmitted to the medulla oblongata, then reaches the cerebral cortex. In the auditory centers of the brain, irritations are analyzed and systematized, as a result of which we hear sounds that fill the world.