Last update: Dec 7th, 2017

Paranasal Sinuses

Introduction to the Paranasal Sinuses:

• The paranasal sinuses are cavities in the bones of the face and cranium.

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• These air – filled spaces vary in size and are lined by mucous membrane.
• The mucous secretions drain into the nasal cavity and help, warm, humidify, and clean the air.
• The paranasal sinuses also help lighten the skull and resonate the voice.

Anterior View:

1. Frontal sinuses – two cavities located just above the orbits and behind the superciliary arches. [Anterior view]

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• Mucous secretions are drained from each sinus by a frontonasal duct, which empties into the nasal cavity at the middle meatus.

Coronal View:

1. Ethmoid sinuses – a collection of small cavities located between the orbits in the lateral masses (or labyrinths) of the ethmoid bone. [Coronal view]

The coronal view of the ethmoid sinuses

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• Each lateral mass contains approximately 6 to 12 cavities, which are referred to as ethmoid air cells.
• The mucous secretions produced by the air cells drain into the nasal cavity at the superior and middle meatuses.

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2. Maxillary sinuses – two large, cavities located in the body of the maxillary bone, on either side of the nasal cavity. [Coronal view]

The coronal view of the maxillary sinuses

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• Mucous produced by each sinus drains into the mid-lateral wall of the nasal cavity.

Sagittal View:

1. Sphenoid sinuses – two cavities (right & left) in the centre (or body) of the sphenoid bone. [Sagittal view]

The sagittal view of the sphenoid sinuses

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• A thin bony septum separates the two sinuses.
• Mucous from the sinuses drains into the spheno-ethmoidal recess located at the top of the nasal cavity.

2. Frontal sinuses – two cavities located just above the orbits and behind the superciliary arches. [Sagittal view]

The sagittal view of the frontal sinus

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• Mucous secretions are drained from each sinus by a frontonasal duct, which empties into the nasal cavity at the middle meatus.

Test yourself:

Anterior view [Show/Hide answers]

Test yourself - anterior view

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Test yourself:

Coronal view [Show/Hide answers]

Test yourself - coronal view

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Test yourself:

Sagittal view [Show/Hide answers]

Test yourself - Sagittal view

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