nostrils

Nostrils, also known as the anterior nares, are the two external openings of the nose. They serve as the entry points to the nasal passages and are separated by the nasal septum. In humans, the nostrils are the visible part of the nose and play a role in breathing and in the sense of smell.

Each nostril leads into the nasal cavity, where air is warmed, humidified, and filtered before reaching the lungs. The outer skin is lined with fine hairs that trap large particles. Inside, mucous membranes produce mucus and are lined with ciliated cells that move mucus and trapped debris toward the throat. The interior also contains turbinates (nasal conchae) that increase surface area to condition the air. The roof houses the olfactory epithelium, which contains receptors for smell.

Functionally, the nostrils act as passages for inhaled air while contributing to its conditioning and filtration. The sense of smell is mediated by receptors in the nasal cavity’s olfactory region, which detect odorants that have dissolved in mucus as they reach the upper nasal area.

Clinical notes commonly address nasal congestion from colds, allergies, or irritants that reduce airflow through one or both nostrils. Structural issues such as a deviated septum or nasal polyps can impair patency. The nasal mucosa is prone to dryness and nosebleeds, and the nasal cycle can cause alternating openness between the two nostrils over time.