Anotia
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Anotia ("no ear") describes a rare congenital deformity that involves the complete absence of the pinna, the outer projected portion of the ear, and narrowing or absence of the ear canal. This contrasts with microtia, in which a small part of the pinna is present. Anotia and microtia may occur unilaterally (only one ear affected) or bilaterally (both ears affected). This deformity results in conductive hearing loss, deafness.
Ear development begins in about the third week of human embryonic development. Beginning with the formation of the Otic Placodes which are an extension of the early hind brain. By the fourth week of development the otic placodes invaginate, or sink inward forming pits which close themselves off for the outer surface ectoderm and begin forming the inner ear labyrinthe on the inside. Outer ear development begins in about the fifth week of human embryonic development. Upon the pharyngeal arches Auricle Hillocks begin to form. By the seventh week the three pairs of hillocks' have enlarged differentiated and fused together to start forming the Pinna, or out portion of the ear. Throughout fetal development the hillocks' will move from the sides of the neck to the sides of the head. simultaneously in the seventh week of development the auditory tube begins to form out of the tympanic membrane.
The human ear is divided into three sections. Each section has possesses its own specialized function.
1. The outer ear acts like a funnel and takes in the sound.
2. The middle ear holds the tympanic membrane, or ear drum and several little bones that are moved by the sound waves that have entered the ear via the canal. These movements are very small, like vibrations and are transmitted to the inner ear.
3. The inner ear contains a structure called the cochlea, which contains small hair- like cells that respond to sound information and transmits it via nerve impulses down the auditory nerve and to the brain, where they are processed.
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