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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 ?
The choanae (posterior nares) were beak shaped, obliquely placed openings located at level of caudal face of second molar tooth and continued caudally into a short passage as nasopharynx (Fig.
Removal is usually achieved via anterior rhinoscopy or endoscopy, although a lateral rhinotomy approach has been required in select cases in which complete removal through the nostrils or the posterior choanae was not possible due to the large size of the mass (13).
mallei in lung and choanae specimens was examined by using standard culturing techniques as described by Wittig et al.
The letters in Charge stand for: Coloboma of the eye, Heart defects, Atresia of the choanae, Retardation of growth and/or development, Genital and/or urinary abnormalities, and Ear abnormalities and deafness.
At posterior rhinoscopy: mucosa of epipharynx was of pink color, its cavity and choanae were free.
2006): Observations on the palate and choanae structures in Mesoeucrocodylia (Archosauria, Crocodylomorpha): Phylogenetic implications.
29) based on common features of the syndrome: C-- coloboma of the eye (missing part of iris and/or retina); H--heart defects; A--atresia of the choanae (bony or membranous blocking of nasal passage); R--retardation of growth and/or development; G--genitourinary anomalies; E--ear anomalies and/or deafness.
The velopharynx closes to prevent food from entering the nasal cavity via the posterior choanae.
4 % eye length; two postrictal tubercles; choanae round or oval, not concealed by palatal shelf of maxillary arch; vomerine odontophores median and posterior to choanae, each about size of a choanae, narrowly separated, each bearing slightly slanted row of 3-5 teeth; tongue oval, its posterior border not notched, posterior Vi not adherent to floor of mouth; vocal slits lateral to tongue; vocal sac subgular.
Prevomers not converging medially; ossified area just behind palatine process; anterior ends somewhat rounded and bluntly serrated; dentigerous processes very slightly rounded and directed posterolaterally, slanted backwards in relation to main axis of cranium; lateral wings moderately developed, bordering choanae, lateral rami pointed and smooth anterolaterally, posterolateral rami slender, four fifths length to neopalatines (Trueb and Cloutier 1991, Trueb 1993), and synchondrotic to sphenethmoid and neopalatines.
Emily was born with CHARGE (coloboma--a cleft, slit, gap, or fissure of the eye; heart defects; atresia of the choanae [a non-closure of one of the communicating passageways in the upper respiratory system]; retardation of growth and development, and central nervous system abnormalities; genital hypoplasia [small genitalia]; and ear abnormalities which affect several functions of her body).
Vocal slits large, extending from beneath postero-lateral margin of tongue to near jaw angle; tongue with a shallow posterior notch; vomerine teeth in two well-separated, transverse rows between posterior halves of obliquely elliptical choanae.