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Anatomy Insight |  Comic  Sans | Lexend

Inside each nostril is a small dilated area called the vestibule, lined by skin containing hairs (vibrissae), sebaceous glands, and mucous glands that help trap large particles such as dust. Deeper in the nasal cavity, the mucosa changes into respiratory and olfactory regions. 

The olfactory region lies mainly over the superior nasal concha and upper septum and contains olfactory receptor cells responsible for smell. 

The respiratory region forms the rest of the cavity and is lined by pseudostratified ciliated columnar epithelium with goblet cells. The mucus traps debris and pathogens, while ciliary action sweeps mucus toward the pharynx to be swallowed. 

• Cold air slows ciliary movement, which may cause mucus buildup and a runny nose. 

Serous glands, lysozyme, defensins, and immune cells provide additional antibacterial protection.

The lateral wall of each nasal cavity contains three projections called the superior, middle, and inferior nasal conchae. 

The superior and middle conchae belong to the ethmoid bone, while the inferior concha is a separate bone. Beneath each concha lies a passageway called a meatus. The conchae increase surface area, warm and humidify inspired air, create turbulence to improve filtration, and help conserve moisture during exhalation.

The superior meatus receives the posterior ethmoidal air cells, while above the superior concha is the sphenoethmoidal recess, into which the sphenoidal sinus opens. The middle meatus contains the bulla ethmoidalis and hiatus semilunaris and receives drainage from the frontal sinus, anterior and middle ethmoidal cells, and maxillary sinus. The inferior meatus receives the nasolacrimal duct.