alveolus
air sac
air cell

A network of air cells constantly adjusts the seat to fit the occupant.

For your purposes, the important question is: are most of the air cells of the final foam open or closed?

Eventually the walls will begin to rupture, and the contents of the air cells escape.

Its air cell, normally on the bottom, was on the side.

The duckling in egg No. 1 had managed to find the air cell and was halfway out of its shell.

The air cell is a small cylindrical chamber with a hole in one end.

The air cell is mounted so as to minimise thermal contact with the mass of the head.

It is present at birth as rudimentary air cells, and develops throughout childhood.

As the fat clumps increase in size, there are also fewer to enclose the air cells.

The surgery used to be a common way to treat an infection in the mastoid air cells.