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air sac

a sac containing air.
alveolus (def 2).
any of certain cavities in a bird's body connected with the lungs.
a saclike dilation of the wall of a trachea in many insects.
Origin of air sac
1820-30 Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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British Dictionary definitions for air sac

air sac

any of the membranous air-filled extensions of the lungs of birds, which increase the efficiency of gaseous exchange in the lungs
any of the thin-walled extensions of the tracheae of insects having a similar function
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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air sac in Medicine

air sac n.
A tiny, thin-walled, capillary-rich sac in the lungs where the exchange of oxygen and carbon dioxide takes place. Also called alveolar sac.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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air sac in Science
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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