Outer ear

The outer ear (auris externa) is an integral part of the ear and includes the pinna, the ear lobe and the external auditory canal. The tympanic membrane represents the boundary between the outer ear and middle ear

In humans is the outer ear and the ear is in this case in particular, a direction- selective filter, which is used for localization of sound sources in the median plane. The various projections and recesses of the external ear in each case form acoustic resonators can be excited with incident sound from a specific direction. This results in directional minima and maxima in the frequency response of the ear sensitivity. By evaluating the maxima and minima in the frequency spectrum of the signal ear can distinguish the hearing if the sound from the front, back, top or bottom is ( direction-determining bands).

With the help of control muscles many mammals can align the ears to a sound source. These are largely regressed in humans and thus the human ear more or less immobile.

The external ear develops from embryonic mesenchymal six cusps, which are covered with ectoderm. Three of the cusp are from the first and three from the second branchial arch. Through the fusion of the cusps to the first branchial cleft formed the ear, while the formation of the outer ear canal and the outer portion of the ear drum by depression of branchial cleft. An incomplete fusion of the pinna cusp is the cause of so-called Aurikularanhänge. It is this almost always only a single small bump in front of the ear, a harmless malformation.

Inflammation of the outer ear is referred to as otitis externa.