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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.



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.

References in periodicals archive ?
Coloboma, congenital heart disease and choanal atresia with multiple anomalies: CHARGE association.
14) Fusion of mediopalatines: The dorsal walls of the choanal fossa of the paired palatine bones (= mediopalatines) were fused or sutured together in the midline for part (usually) or all of their length, except in Pyrenestes and Hypargos and a few scattered specimens (no entire species) in other genera.
Mutation of the gene encoding human TTF-2 associated with thyroid agenesis, cleft palate and choanal atresia.
Like in vipers and other hydrophiine elapids, but not elapines, the palatine of Acanthophis has no connections to the maxilla, choanal passage, or snout, potentially allowing greater excursions of the jaw apparatus.
narrow nostrils, wide columella, enlarged turbinates, deviated septum, polyps, nasopharyngeal adenoid tissue, decreased posterior choanal height, constricted luminal valves, external nasal deformity) and oropharyngeal abnormalities (e.
Numerous other less common associations have been described, including choanal atresia, vesicoureteric reflux, conductive hearing loss, and recurrent respiratory infections [1, 4, 6, 7].
Disorders such as Down syndrome, Pierre Robin syndrome (a disorder characterized by abnormally small jaw, displaced tongue, and cleft palate), choanal atresia (absence of the opening from the nasal passage to the windpipe), and others, can cause associated sleep-disordered breathing.
Choanal polyps have frequently been described as arising from the maxillary sinus (1) and have been infrequently reported to be arising from the sphenoid sinus.
Intralesional cisplatin chemotherapy and topical cryotherapy for the control of choanal squamous cell carcinoma in an African penguin (Spheniscus demersus).
Colobomas can occur as an isolated congenital abnormality or as part of a syndromic setting, including CHARGE (Coloboma, Heart malformations, choanal AtResia, Growth and/or mental retardation, genital anomalies, Ear anomalies and/or deafness), VATER (Vertebrae, Anus, Trachea, Esophagus, and Renal), branchio-oculo facial, Meckel-Gruber, Walker-Warburg, and Goldenhar syndromes; Aicardi, basal cell nevus; and Trisomy 13 and 18.
2) Osteogenesis imperfecta patients present with multiple fractures; however, these are more severe than in pycnodysostosis, and have associated features such as choanal atresia and blue sclera.
The nonrandom association of coloboma, choanal atresia, retardation of growth and development, and genital and ear anomalies are frequently present in various combinations and degrees in individuals with CHARGE syndrome (Tegay & Yedowitz, 2009).