Nasal cavities and sinuses filter, warm, and humidify air, as well as detect smells.
The nasal cavities are separated into right and left halves by a partition called the nasal septum, made of bone and cartilage.
Nasal cavities contain several drainage openings including:
- paranasal sinuses (sinuses of the maxillary, frontal, ethmoidal, and sphenoidal) from where mucus drains into the nasal cavity
- nasolacrimal ducts from where tears drain into the nasal cavity
Nasal cavities also contain receptor cells for the sense of smell. Olfactory organs cover the upper parts of the nasal cavity and a part of the nasal septum.
Air enters through two openings in the nose called the nostrils or nares.
Nasal conchae are three bony projections that appear on the lateral walls of the nasal cavities. They increase the surface area of the cavities and support the ciliated mucous membrane lining the nasal cavities.
The mucous membrane contains mucus-secreting cells and blood vessels which warms air and traps dust and other particles to the sticky mucus.
Paranasal sinuses are found on each side of the nose from the forehead to the cheek and include the following:
- two frontal sinuses
- six ethmoidal sinuses
- two sphenoidal sinuses
- two maxillary sinuses