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The paranasal sinuses are air-filled cavities within the facial bones and skull base that are lined by respiratory mucosa (ciliated pseudostratified columnar epithelium) and communicate with the nasal cavity.

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• Functions: lightening skull weight, humidifying inspired air, resonance of voice, and contributing to immunological defense.

https://youtu.be/v7NHFGKBvjg

https://youtu.be/LpLCsj8_oeo

https://youtu.be/O8n6WeDAjos

Anatomy of PNS

1. Maxillary Sinus

• Largest sinus (~15 mL).
• Pyramidal in shape, located in maxilla.
• Drainage: via ostiomeatal complex into middle meatus.
• Related to: orbit (roof), teeth (floor), nasal cavity (medial wall).

2. Frontal Sinus

• Located in frontal bone, above orbit.
• Drains via frontonasal duct into middle meatus.
• Variable size; may be absent.

3. Ethmoid Sinuses (Ethmoid air cells)

• Multiple small air cells in ethmoid bone between orbits.
• Divided into: anterior, middle, posterior.
• Drainage:
  • Anterior & middle → middle meatus (ostiomeatal complex).
  • Posterior → superior meatus.