Paranasal sinuses
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Paranasal sinuses are air-filled cavities in the bones around the nose. There are four paired sinuses:
- Maxillary sinuses: Located under the eyes
- Frontal sinuses: Located above the eyes
- Ethmoidal sinuses: Located between the eyes
- Sphenoidal sinuses: Located behind the eyes
The paranasal sinuses are named according to the bone in which they are located. They are found in three bones of the neurocranium (braincase), the frontal bone, ethmoid bone, and sphenoid bone. The maxilla is the only facial bone (viscerocranium) that contains its own sinuses.
The paranasal sinuses are lined with cells that make mucus, which keeps the inside of the nose from drying out during breathing.
The paranasal sinuses are believed to be implicated in several roles, including:
- Decreasing the relative weight of the skull
- Increasing the resonance of the voice
- Providing a buffer against facial trauma
- Insulating sensitive structures from rapid temperature fluctuations in the nose
- Humidifying and heating inspired air
