Mastoid air cells

Last revised by Raymond Chieng on 8 Jun 2023

The mastoid air cells (cellulae mastoideae) represent the pneumatization of the mastoid part of the temporal bone and are of variable size and extent. 

At the superior and anterior part of the mastoid process the air cells are large and irregular and contain air, but toward the inferior part they diminish in size, while those at the apex of the process are frequently quite small and contain marrow. Occasionally, they are entirely absent.

Mastoid air cells communicate with the middle ear via the mastoid antrum and the aditus ad antrum

The mastoid air cells are traversed by the Koerner septum, a thin bony structure formed by the petrosquamous suture that extends posteriorly from the epitympanum, separating the mastoid air cells into medial and lateral compartments.

Mastoid process develops at birth, from petromastoid part of temporal bone and fused with squamozygomatic part and tympanic part of the temporal bone. The growth of mastoid process accelerates between age two to five, and completes by age six 5.

Pneumatization of mastoid process begins at infancy, and completes at the age of six 5.

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