air sac

Science Dictionary
air sac  
  1. An air-filled space in the body of a bird that forms a connection between the lungs and bone cavities and aids in breathing and temperature regulation.

  2. See alveolus.

  3. A saclike enlargement in the trachea of an insect.

  4. A baglike piece of skin or tissue below the jaw of certain animals, such as the bullfrog and orangutan, that can be inflated to increase sound production.


The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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