air sac


air sac
1. a sac containing air.
2. alveolus (def. 2).
3. any of certain cavities in a bird's body connected with the lungs.
4. a saclike dilation of the wall of a trachea in many insects.
[1820-30]

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      any of the air-filled extensions of the breathing apparatus of many animals. Air sacs are found as tiny sacs off the larger breathing tubes (tracheae) of insects, as extensions of the lungs in birds, and as end organs in the lungs of certain other vertebrates. They serve to increase respiratory efficiency by providing a large surface area for gas exchange. See also pulmonary alveolus.

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Universalium. 2010.

Look at other dictionaries:

  • Air sac — 1. (Anat.) One of the spaces in different parts of the bodies of birds, which are filled with air and connected with the air passages of the lungs; an air cell. [1913 Webster] 2. An {alveolus}. [PJC] …   The Collaborative International Dictionary of English

  • Air sac — is an anatomical term with several meanings: * Pulmonary alveolus, informally known as an air sac, one of innumerable spherical outcroppings of the respiratory bronchioles in the mammalian lung, the secondary sites of gas exchange with the blood… …   Wikipedia

  • air sac — n ALVEOLUS (b) * * * 1. in birds, one of the air filled cavities connected with the air passages of the lungs and usually with cavities in the bones; they assist in respiration and lower the body s specific gravity. Domestic fowl have one or two… …   Medical dictionary

  • air sac — n. any of the air filled cavities in a bird s body, having connections to the lungs …   English World dictionary

  • air-sac — airˈ sac noun 1. An alveolus, or the cluster of alveoli, at the termination of a bronchiole in the lungs 2. An outgrowth of the lung in birds, helping respiration or lightening the body 3. In insects, a dilatation of the trachea • • • Main Entry …   Useful english dictionary

  • air sac — air′ sac n. 1) anat. alveolus 2) 2) orn any of certain cavities in a bird s body connected with the lungs • Etymology: 1820–30 …   From formal English to slang

  • air sac — noun 1. a tiny sac for holding air in the lungs; formed by the terminal dilation of tiny air passageways • Syn: ↑alveolus, ↑air cell • Derivationally related forms: ↑alveolate (for: ↑alveolus) • Hypernyms …   Useful english dictionary

  • air sac — gas bladder, a thin membranous, sometimes alveolated sac in the dorsal portion of the abdominal cavity. Contains a varying mixture of gases, not identical to the composition of air. May be one, two or three chambered. May be connected to the gut… …   Dictionary of ichthyology

  • air sac — /ˈɛə sæk/ (say air sak) noun 1. a sac containing air. 2. any of certain cavities in a bird s body connected with the lungs. 3. a saclike dilatation of an insect trachea …   Australian English dictionary

  • air sac — noun Date: circa 1828 1. one of the air filled spaces in the body of a bird connected with the air passages of the lungs 2. alveolus 1b 3. a thin walled dilation of a trachea occurring in many insects …   New Collegiate Dictionary


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