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nasal cavity[′nā·zəl ¦kav·əd·ē]
the cavity in which the olfactory organs of vertebrate animals are located. In terrestrial vertebrates and in man, the nasal cavity is also the initial division of the respiratory tract.
The nasal cavity is unpaired in cyclostomes and paired in fish. In all pulmonate organisms, the paired nasal cavity opens to the outside through external nasal orifices. The nasal and oral cavities are connected by means of choanae in lungfishes, amphibians, the majority of reptiles, and birds. In animals with a hard palate—crocodiles, mammals, and man—the nasal cavity is connected with the nasopharynx; in this case, the posterior section of the nasal cavity extends into the nasopharyngeal canal. In amniotes and man, the anterior section of the nasal cavity is called the vestibule.
In all terrestrial vertebrates the nasal cavity is divided by the maxilloturbinal bone into two sections: the superior nasal meatus and the inferior nasal meatus. In birds and the majority of mammals the superior nasal meatus contains the concha nasalis, or the turbinate bone. In mammals and man the posterior section of the nasal cavity contains the conchae of the ethmoid bone, which are covered by olfactory epithelium. All terrestrial vertebrates have a nasolacrimal canal that connects the eye socket with the nasal cavity; in most of these animals, Jacobson’s organ is formed by an outgrowth of the nasal cavity. In crocodiles, birds, and especially mammals and man, the nasal cavity is connected with the air cavities in the cranial bones.
N. S. LEBEDKINA