Atresia

Atresia is a condition in which a body orifice or passage in the body is abnormally closed or absent.

Examples of atresia include:
 * Biliary atresia
 * Ovarian follicle atresia, atresia refers to the degeneration and subsequent resorption of one or more immature ovarian follicles.
 * Vaginal atresia - congenital occlusion of the vagina or subsequence adhesion (sticking together) of the walls of the vagina occluding it.
 * Esophageal atresia - affects the alimentary tract causing the esophagus to end before connecting normally to the stomach.
 * Choanal atresia - blockage of the back of the nasal passage, usually by abnormal bony or soft tissue.
 * Anorectal atresia - malformation of the opening between the rectum and anus.
 * Pulmonary atresia - malformation of the pulmonary valve in which the valve orifice fails to develop.
 * Aural atresia (see Microtia) - a congenital deformity of the pinna (outer ear).
 * Intestinal atresia - malformation of the intestine