Atresia is a condition in which an orifice or passage in the body is (usually abnormally) closed or absent.Examples of atresia include:
Aural atresia, a congenital deformity where the ear canal is underdeveloped.
Biliary atresia, a condition in newborns in which the common bile duct between the liver and the small intestine is blocked or absent. [Source: Wikipedia 
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