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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 ?
1 The abbreviation "CHARGE" characterizes the association of coloboma, heart anomalies, choanal atresia, and retardation of growth, genital and ear anomalies.
David (a pseudonym) was an older adolescent who exhibited many major features of CHARGE syndrome including coloboma of the eye, heart defect, choanal atresia, ear anomalies, and small stature, as well as a cleft palate and facial paralysis.
Table 1: types of lasers used for common conditions in ORL surgeries Common conditions treated by laser Types of laser used in ORL surgery Nasal surgery: Nasal and paranasal polypi, hypertrophied CO2, Nd:YAG, Ho: YAG, turbinates, concha bullosa media, Diode and KTP Lasers Synechia, cicatricial stenosis and granulation, Septum spear and septal crest, talengectasia and capilary hemangioma, adenoids and choanal atresia.
5 LMA gave a reliable airway in case 7 with PRS and choanal atresia and this acted as a conduit for fibreoptic intubation advancement of an adjacent bougie.
On the other hand, women who have Grave's disease that is diagnosed in the first trimester of pregnancy should be started on PTU, because methimazole is associated with certain birth defects such as cutis aplasia and choanal or esophageal atresia, Dr.
Exposure to sulfonamides was associated with the most defects, including anencephaly, hypoplastic left heart syndrome, coarctation of the aorta, choanal atresia, and transverse limb deficiency.
A baby in the special senses category had bilateral choanal atresia and two babies had ear malformations associated with internal abnormalities.
It has also successfully conducted bilateral choanal atresia surgery ti save lives of newborn babies, said Francesca.
In the past, PTU was considered the drug of choice for treatment of hyperthyroidism in pregnancy because clinicians believed it crossed the placenta to a lesser degree than did methimazole, and because methimazole was associated with fetal esophageal and choanal atresia and fetal cutis aplasia (congenital skin defect of the scalp).
Coloboma, congenital heart disease and choanal atresia with multiple anomalies: CHARGE association.