atresia

1. The absence or closure of a normal body orifice or tubular passage such as the anus, intestine, or external ear canal.
2. The degeneration and resorption of one or more ovarian follicles before a state of maturity has been reached.

[New Latin atrēsia : Greek a-, not, without; see a-¹ + Greek trēsis, perforation, orifice.]

The congenital absence or occlusion of a normal opening of one or more ducts in an organ.

Congenital absence or closure of a normal body opening or tubular structure.

• anal a., a. ani — see anal atresia.
• aortic a. — absence of the opening from the left ventricle of the heart into the aorta.
• aural a. — absence of closure of the auditory canal.
• biliary a. — congenital obliteration or hypoplasia of one or more components of the bile ducts, resulting in persistent jaundice and liver damage.
• choanal a. — see imperforate buccopharyngeal membrane.
• follicular a., a. folliculi — premature degeneration and resorption of a graafian follicle of the ovary. It may be postovulatory or preovulatory atresia. It is a normal occurrence when several ova mature together. Abnormal atresia may be a cause of anestrus.
• ileal a., a. ilei — the congenital obstruction in calves may cause sufficient abdominal distention to result in dystocia.
• inherited alimentary tract segmental a. — occurs in cattle and horses. A variety of segments are involved, including ileum, colon, rectum and anus.
• jejunal a., a. jejuni — resembles ileal atresia clinically.
• lacrimal puncta a. — atresia of the lacrimal puncta causing tearing from birth.
• mesonephric duct a. — causes stenosis or aplasia of epididymis or ductus deferens.
• nasolacrimal duct a. — atresia of the nasolacrimal duct causing tearing from birth.
• paramesonephric duct a. — causes uterus unicornis or duplex uterus or segmental aplasia of a uterine horn or tube.
• rectal a., a. recti — congenital absence of luminal development leading to abdominal distention after birth. There is obvious absence of feces and staining and inability to pass a sound.
• salivary duct a. — congenital atresia causes distention of the gland followed by atrophy.
• tracheal a. — common in English bulldogs; may be segmental or affect the entire length of the tube.
• tricuspid a. — absence of the opening between the right atrium and right ventricle, circulation being made possible by an atrial septal defect.

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

Examples of atresia include:

• Anorectal atresia - malformation of the opening between the rectum and anus.
• Aural (External Auditory Canal) atresia- Absence of the ear canal or failure of the canal to be tubular or fully formed (can be related to Microtia- a congenital deformity of the pinna (outer ear).)
• Biliary atresia - Condition in newborns in which the common bile duct between the liver and the small intestine is blocked or absent.
• Choanal atresia - blockage of the back of the nasal passage, usually by abnormal bony or soft tissue.
• Esophageal atresia - affects the alimentary tract causing the esophagus to end before connecting normally to the stomach.
• Intestinal atresia - malformation of the intestine, usually resulting from a vascular accident in utero
• Ovarian follicle atresia, atresia refers to the degeneration and subsequent resorption of one or more immature ovarian follicles.
• Pulmonary atresia - malformation of the pulmonary valve in which the valve orifice fails to develop.
• Tricuspid atresia - a form of congenital heart disease whereby there is a complete absence of the tricuspid valve. Therefore, there is an absence of right atrioventricular connection.
• Vaginal atresia - congenital occlusion (blocking) of the vagina or subsequence adhesion (sticking together) of the walls of the vagina occluding it.

• Renal Atresia - congenital decreased size of the kidney leading absolute no functionality of the kidney .It is usually related to a single kidney.

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