Mastoid cell

A mastoid cell (mastoid sinus) is an air pocket in the mastoid process, which is a part of the temporal bone of the skull located just behind the ear. They are also more appropriately called mastoid sinuses as they are air pockets and not cells in the usual biological sense. The mastoid process contains many small mastoid cells.

The function of mastoid cells is yet unclear. One researcher suggests that the mastoid cells may buffer the inner ear from changes in temperature, by insulating it from the outside environment, and pressure by acting as a store of air.