Choana


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Related to Choana: antrochoanal polyp, Torus tubarius

choana

[′kō·ə·nə]
(anatomy)
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.

Choana

 

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 ?
Axial and coronal computed tomography (CT) of the nose and paranasal sinuses demonstrated a soft-tissue opacity filling the left sphenoid sinus and extending into the choana (figure 2).
The pedicle of the sphenochoanal polyp was seen protruding through the left sphenoid ostium into the sphenoethmoid recess and extending into the choana.
Electrocautery was performed to excise the mass at its superior portion near the right choana.
The inferior turbinate should be examined from the naris anteriorly to the choana posteriorly.
Several white plaques were present on the oral mucosa around the choana, and yellow nodules were present on the tongue.
The enlarged antral polyp protrudes through the maxillary infundibulum or accessory ostium into the middle meatus and then the posterior choana, with possible extension into the posterior nasopharynx.
After resection at its origin, it was found to be filling the inferior right nasal airway (figure 2, A) and extending back to the right posterior choana.
Mucoid debris was flushed through the choana, and fluid also exited the fistula near the right commissure, confirming the connection between the sinuses and periorbital spaces.
1) The posterior septal branch of the sphenopalatine artery, also known as the nasoseptal branch, passes horizontally in the lateral-medial direction between the natural ostium of the sphenoid sinus and the choana (figure).