Mastoid Cells


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Mastoid Cells

 

air-filled sacs of the floor and external walls of the tympanic cavity in most mammals. They are formed of tympanic bone, an angular bone homologous to the lower jaw in reptiles. Primitive mastoid cells protect the auditory ossicles and tympanic cavity. Increasing complication of the mastoid cells converts them into acoustic resonators or absorbers. Four types of eardrums are distinguished: spherical, chambered, large-cellular, and spongy-small-cellular. The functions of each type are determined by the acoustic properties of the animals’ habitat and characteristics of their orientation.

G. N. SIMKIN

References in periodicals archive ?
1,2,6) Occlusion of the lateral sinus as a result of a nonseptic thrombus impairs venous drainage from the mastoid cells, resulting in venous congestion, interstitial edema, and transudation of fluid into the air spaces.
Most of these anomalies manifested as mild opacification in a few mastoid cells or as evidence of mastoid sclerosis without signs of active disease.
Computed tomography (CT) showed a loss of aeration in the mastoid cells on the left (figure 1).