narinas

Narinas, also called nares, are the external openings of the nasal cavity. There are two narinas in the human nose, one on each side, and the term narina refers to a single opening. The two narinas are separated by the nasal septum, but each leads into its corresponding nasal vestibule.

Anatomically, each narina opens into the nasal vestibule, which is bounded at the entrance by the alae of the nose. The vestibule is lined at the surface by keratinized stratified squamous epithelium with coarse hairs (vibrissae) that help filter large particles. Deeper within the nasal cavity, the lining switches to respiratory mucosa, comprised mainly of pseudostratified ciliated columnar epithelium, which participates in humidifying and warming inspired air.

Functionally, the narinas serve as the primary entry points for inhaled air. They contribute to the regulation of airflow and resistance, assist in filtration through nasal hairs, and help condition the air by humidifying and warming it before it reaches the lower respiratory tract. By directing air toward the olfactory region at the roof of the nasal cavity, the narinas also support the sense of smell, though the olfactory receptors reside higher up in the nasal cavity.

Clinical relevance and variation: Narina patency can be affected by conditions such as rhinitis, allergies, infections, trauma, or nasal polyps, leading to obstruction or altered breathing. Congenital or acquired changes in nasal structure, including deviations of the nasal septum or valve area, can influence narina size and airflow. Treatments may include medical management of inflammation or, in some cases, surgical interventions to restore patency.