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A funnel-shaped opening, especially the posterior nares.
(invertebrate zoology)
A protoplasmic collar surrounding the basal ends of the flagella in certain flagellates and in the choanocytes of sponges.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



an internal nasal orifice in vertebrates, including man. Choanae evolved after the development of constant or periodic breathing of air. They first arose in crossopterygian and dipnoan fish. In dipnoan embryos, grooves starting from the olfactory sacs change into canals whose internal orifices, or primary choanae, open into the oral cavity. In dipnoan fish, with aquatic respiration, air flows to the lungs through the canals. In terrestrial vertebrates, a naso-oral canal forms during embryonic development and connects with the external nasal orifices, or nostrils, to the oral cavity, where it opens into the primary choanae. In amphibians the choanae remain in this position throughout life. In mammals and in some reptiles and birds the upper part of the oral cavity into which the primary choanae open becomes separated from the lower part because of the development of the secondary hard palate; it forms the nasopharyngeal duct, which opens into the pharyngeal cavity through the secondary choanae. In crocodiles, some birds, and especially mammals the secondary choanae recede farther into the pharynx as the secondary hard palate lengthens. The formation of a nasopharyngeal duct separated from the lower part of the oral cavity and the recession of the choanae close to the larynx enable animals and humans to breathe freely when food is in the oral cavity.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
The major criteria of CHARGE syndrome include coloboma, choanal atresia, and/or characteristic ear anomalies (Chen, 2017).
However, the combination of a mini-Caldwell and endoscopic approaches is needed for the complete removal of CPs if the endonasal technique fails.[3] When a huge CP extending into the oropharynx is encountered, the choanal component can be more easily removed via the transoral route.
Webbed fingers and toes, large floppy ears, choanal atresia, nasolacrimal duct obstruction, cryptorchidism and inguinal hernia are some of the other frequent clinical findings.
Kristiansson, "Hereditary intractable diarrhoea with choanal atresia - a new familial syndrome," Journal of Pediatric Gastroenterology & Nutrition, vol.
Twin A, however, passed away from complication of presumed necrotizing enterocolitis with bowel perforation following admission for repair of her choanal atresia at three months of age.
The CHD7 gene encodes a chromatin-remodeling factor and is mutant in CHARGE syndrome, which has the constellation of Colobomata, Heart Anomalies, choanal Atresia, Retardation, Genital and Ear anomalies (42).
Preterm babies with meconium aspiration, congenital pneumonia, congenital anomalies like choanal atresia, tracheo-oesophageal fistula and diaphragmatic hernia.
Digital palpation of the nasopharynx was performed just before curettageto assess adenoid site, size, and degree of choanal occlusion, and then just after removal to determine whether there were any remnants and assess the opening of the posterior choana.
([dagger][dagger][dagger]) Cleft lip with cleft palate (749.20-749.25), cleft palate without cleft lip (749.00-749.04), cleft lip (749.10-749.14), or choanal atresia (748.0).
Heinz et al., "Mutation of the gene encoding human TTF-2 associated with thyroid agenesis, cleft palate and choanal atresia," Nature Genetics, vol.