Air bladder and Air cell

Air bladder noun - An air-filled sac near the spinal column in many fishes that helps maintain buoyancy.

Air cell and air bladder are semantically related. In some cases you can replace phrase "Air cell" with "Air bladder", this phrases are similar.

Air cell noun - A tiny sac for holding air in the lungs; formed by the terminal dilation of tiny air passageways.

Air bladder and air cell are semantically related. You can use "Air bladder" instead a noun phrase "Air cell".