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Anotia
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.
== Developmental biology of the ear ==
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.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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