Ethmoid sinus

The ethmoid sinus, one of the paranasal sinuses, is the collective name for the ethmoidal air cells.

Each ethmoid sinus is an air-space enclosed within the ethmoid bone. The ethmoidal air cells consist of numerous thin-walled cavities situated in the ethmoidal labyrinth and completed by the frontal, maxilla, lacrimal, sphenoidal, and palatine bones.

They lie between the upper parts of the nasal cavities and the orbits, and are separated from these cavities by thin bony laminæ.

Three groups
Anatomically, ethmoidal sinuses can be classified as the anterior, middle, and posterior ethmoid sinuses.


 * The posterior drains into the superior meatus under cover of the superior nasal concha; sometimes one or more opens into the sphenoidal sinus.


 * The middle drains into the middle meatus of the nose on or above the bulla ethmoidalis.


 * The anterior drains into the middle meatus of the nose by way of the infundibulum.

Innervation
The ethmoidal air cells are innervated by the anterior and posterior ethmoidal nerves, and the orbital branches of the pterygopalatine ganglion.