Outer ear
The outer ear ( auris externa ) is part of the ear and includes the auricle and the external auditory canal , in humans also the earlobe . The eardrum is the border between the outer and middle ear .
Layout and function
The auricle is a directionally selective filter that is used to localize sound sources in the median plane . The numerous elevations and depressions of the auricle each form acoustic resonators , which are excited from a certain direction when sound is incident. This results in direction-dependent minima and maxima in the frequency response of the ear sensitivity. By evaluating the maxima and minima in the frequency spectrum of the ear signal, the hearing can distinguish whether sound comes from the front, back, above or below ( direction-determining bands ).
With the help of adjuster muscles, many mammals can align their auricles to a sound source. These are largely regressed in humans and thus the human ears are more or less immobile.
The outer ear develops embryonically from six mesenchymal cusps, which are covered with ectoderm . Three of the humps come from the first and three from the second gill arch . The auricle is created by the merging of the cusps around the first gill groove, while the outer auditory canal and the outer part of the eardrum are formed by sinking the gill groove. An incomplete fusion of the auricle humps is the cause of the so-called auricular appendages. There is usually only a single small bump in front of the auricle, a harmless deformity.
Diseases
An inflammation of the outer ear is called otitis externa called.
See also
literature
- Uwe Gille: Ear, Auris . In: Franz-Viktor Salomon (Ed.): Anatomy for veterinary medicine . 2nd Edition. Enke, Stuttgart 2008, ISBN 978-3-8304-1075-1 , pp. 612-621 .
