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.
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.
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