Pneumatized

Pneumatized is an adjective used in anatomy to describe tissues or bones that contain air-filled cavities. In vertebrates, bones or spaces described as pneumatized have been invaded by air-filled cavities that communicate with the respiratory system. Pneumatization typically occurs when diverticula from the lungs or air sacs extend into developing bone, forming a network of connected air spaces lined with mucosa.

Paranasal sinuses (maxillary, frontal, ethmoidal, sphenoidal) are classic human examples of pneumatized bones; the mastoid air cells of the temporal bone are another well-known example.

In birds, extensive skeletal pneumatization is common, with many skull bones, the vertebrae, and limb bones featuring air spaces that extend from the bird's air sac system. This adaptation reduces skeletal weight and is part of the avian respiratory design that supports flight. Evidence of pneumatized bones in extinct dinosaurs, including theropods, has been cited as supporting the presence of air sacs and a flow-through respiratory system related to flight in the avian lineage.

Beyond birds and humans, pneumatization occurs in various taxa and tissues, reflecting different functional pressures. The term is often used in radiology and comparative anatomy to distinguish air-filled from solid bone or tissue.