Britannica Sources used in this answer

How does the nose filter, warm, and moisten inhaled air?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Illustration showing different animals and their respiratory organs: a spider with book lungs, a chicken with lungs, a sponge with labeled inflow and outflow pores, a fish with gills, and a caterpillar with spiracles. — Respiratory system Different methods of respiration in animals.

The nose conditions inhaled air through a specialized structural design within the nasal cavity that prepares it for the delicate tissues of the lower respiratory tract.1

Filtering

The process begins at the vestibule, the entrance to the nose, which contains short, thick hairs called vibrissae that trap large particles. Further inside, the respiratory area is lined with a mucous membrane that secretes mucus. This sticky layer traps smaller debris, such as dust, soot, and bacteria. Fine, hairlike projections known as cilia then work to collect and move this trapped debris.12

Warming and Moistening

The nasal cavity is lined with a respiratory mucosa that contains venous plexuses. These networks of blood vessels help warm the air as it passes through. Additionally, the mucosa contains mucus-secreting glands that add moisture to the air, ensuring it is properly humidified before reaching the lungs. The complex shape of the cavity, created by bony ridges called nasal conchae, increases the surface area for these conditioning processes to occur efficiently.12