0 a space filled with air that continues from a bird's lungs into one of its bones or another body area, used in breathing --
These sounds are reflected by the dense concave bone of the cranium and an air sac at its base.
While the left abdominal air sac is large and lies to the left of the mesentery.
The big end contains the air sac and its shell is pierced by a higher density of pores than the more pointed end.
Air sac extensions from the lungs occupy the centre of some bones.
The ribbon seal has a large inflatable air sac that is connected to the trachea and extends on the right side over the ribs.
The syrinx and sometimes a surrounding air sac resonate to sound waves that are made by membranes past which the bird forces air.
Such an organ is generally a membrane (tympanum) stretched across a frame backed by an air sac and associated sensory neurons.
Air from the lungs is channeled to the air sac, which resonates to make the sound louder.
