atresia /atre·sia/ (ah-tre´zhah) congenital absence or closure of a normal body opening or tubular structure.atret´ic
anal atresia , atresia a´ni imperforate anus.
aortic atresia congenital absence of the aortic orifice.
biliary atresia obliteration or hypoplasia of part of the bile ducts due to arrested fetal development, causing persistent jaundice and liver damage ranging from biliary stasis to biliary cirrhosis, with splenomegaly as portal hypertension progresses.
follicular atresia degeneration and resorption of an ovarian follicle before it reaches maturity and ruptures.
laryngeal atresia congenital lack of the normal opening into the larynx.
mitral atresia congenital obliteration of the mitral orifice, often associated with hypoplastic left heart syndrome or transposition on great vessels.
prepyloric atresia pyloric atresia; congenital membranous obstruction of the gastric outlet, with vomiting of gastric contents only.
pulmonary atresia congenital severe narrowing or obstruction of the pulmonary orifice, with cardiomegaly, reduced pulmonary vascularity, and right ventricular atrophy. It is usually associated with tetralogy of Fallot, transposition of great vessels, or other cardiovascular anomalies.
pyloric atresia prepyloric a.
tricuspid atresia congenital absence of the tricuspid orifice, circulation being made possible by the presence of an atrial septal defect. 
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Tricuspid atresia, here displaying a ventricular septal defect and normally related great arteries, the arrows showing the altered flow of blood through the heart.
urethral atresia congenital imperforation of the urethra.
| follicular atresia n. The normal process affecting the ovarian primordial follicles in which death of the ovum results in cystic degeneration followed by cicatricial closure. |
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