Some species are devoid of hair in the lower (proximal) ear canal (eg horse) hair follicle density in the dog is variable – usually simple but in some breeds compound hair follicles.įoreign bodies can become lodged in the external auditory meatus, but glands are present that produce wax which can trap these. The density of hair follicles on the concave pinna is variable, as is the density and distribution of hair follicles in the ear canal itself. The skin of the normal ear has a thin stratified keratinising epidermis and a thin dermis containing adnexal structures – hair follicles, sebaceous and apocrine glands. The cartilage and bony process of the external ear and the tympanic membrane are covered by skin. ![]() The vertical ear canal lies in a rostroventral orientation before bending medially to become the horizontal canal. The annular cartilage lies between the proximal horizontal ear canal and the bony acoustic process of the tympanic bulla, connected by ligaments. The scutiform cartilage lies rostromedially in the lower ear canal and provides support. Proximally, the auricular cartilage is rolled into a funnel shape, known as the concha. There are also irregularities on the concave surface with ridges and prominences, the medial and lateral crus of the helix on the medial aspect of the opening of the external ear canal, opposite the rectangular tragus on the lateral aspect. The hair covering on the convex side is usually similar to the rest of the body but the hair covering on the concave or medial aspect is variable. The auricular cartilage is flared distally into a flattened cone shape, covered by skin on both sides - more tightly on the medial or concave side than the convex side. (8) The brain’s “ processing centres” link the incoming impulses of acoustic frequencies with the relevant information, and we understand what we have just heard.The pinna consists of the auricular cartilage, and skin which allows for flexibility and elasticity. Here the signals from both ears are processed together. (7) In the brain stem they are allocated to the appropriate “processing centre” in the brain. (6) The acoustic nerve receives the impulses and passes them to the brain stem. Electric impulses are created in its approximately 20,000 hearing cells. This is where the actual spiral organ (of Corti) is located. (5) In the inner ear, the cochlea, the liquid causes the basilar membrane to vibrate. These bones convert the vibrations in the air into liquid movement which then reach the inner ear. The smallest bones in the body (malleus, incus and stapes which combine to form the ossicular chain) can be found there. It is filled with air that enters from the nasopharynx via the so-called Eustachian tube. (4) The middle ear is a cavity also known as the "tympanic cavity". (3) The eardrum then passes the vibrations on to the middle ear. (2) These vibrations are carried through the auditory canal to the eardrum. The shape of the auricle supports the ability of the ear to locate sound sources. The sound waves from the environment that reach the outer ear in the form of air movements are bundled and transmitted through the auditory canal. (1) The outer ear consists of the auricle and the auditory canal, which is up to about 3.5 centimetres long. The auditory components: The ear and its structure and function Our hearing therefore functions selectively. The healthy ear is able to pass on the sound in such a way that the useful sound can be filtered out in the brain. On the other hand, there are the unimportant or even disturbing noises such as machine noise, the traffic and babble of voices. ![]() Important signals include, for example, the voice of a familiar person, a certain type of music or an announcement on a train platform. Via the auditory nerve, the sound information thus processed reaches the auditory centre of the brain, where it is decoded.ĭuring the hearing process, sound processing takes place which differentiates between important and unimportant sound signals. The inner ear with the auditory nerve then converts the alternating pressure into electrical nerve impulses. The sound first passes through the auditory canal of the outer ear, then the middle ear. But the ear is much more than that, and it is precisely the other part which makes the wonder of hearing possible. When we speak about the ear we normally mean the auricle, the part of the ear we can see. The ear - How hearing and sound processing work
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