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Outer ear
Last reviewed: 23.11.2021
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The external ear (auris externa) includes the auricle and the external auditory meatus, which form a kind of funnel for catching sounds and directing the sound wave to the eardrum.
The auricula is based on a complex form of elastic cartilage (cartilago auriculae), covered with a densely attached skin to the cartilage. There is no cartilage in the lower part of the auricle. Instead, there is a skin fold with a fat tissue inside - a lobulus auriculae - a lobe. The free edge of the shell is wrapped, forms a curl (helix), which ends in the anterior part of the shell over the external ear canal in the form of a crus helicis.
The external ear canal (meatus acusticus externus), open from the outside, ends blindly in the interior, separating from the middle ear cavity by the tympanic membrane. The length of the ear canal in an adult is an average of 35 mm, the diameter reaches 9 mm at the beginning and 6 mm in the narrowest place, where the cartilaginous external auditory canal passes into the bone.
The drum membrane (membrana tympani) is a thin translucent oval plate measuring 11x9 mm, separating the external auditory canal from the drum cavity (middle ear). The tympanic membrane is fixed at the end of the ear canal, in the groove of the drum part of the temporal bone. The large lower part of the membrane is a stretched part (pars tensa), and the upper part, approximately 2 mm in width, adjacent to the scaly part of the temporal bone, is called the not straightened part (pars flaccida).
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