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   Ethmoidal air sinuses are thin walled air cavities in the lateral masses of ethmoid bone occupting medial wall of orbit & upper third of lateral wall of nose.

CELLS: 3-18 in number.


                         ETHMOIDAL AIR SINUS


A)      ANTERIOR GROUP: 1. Agger Nasi cells. 2. Ethmoid bulla. 3. Supra orbital cells. 4. Fronto ethmoid cells. 5. Haller cells. Consists of anterior & meddle air cell. Separated from posterior group of basal lamina. Drain into middle meatus.

B)      POSTERIOR GROUP: 1-7 in number. Spheno ethmoidal cell- onodi cell. Open into superior or supreme meatus. Optic nerve & carotid artery are related to it.


1.       ROOF: Fovea ethmoidalis & related to anterior cranial fossa.

2.       LATERAL WALL: A papery thin bone, Lamina propria & related to orbit & cranial sac.

3.       POSTEROLATERAL WALL: Related to sphenoid sinus.

4.       MEDIAL WALL: Related to nasal cavity.

A semi-circular opening drains into infundibulum of osteomeatal complex.