Air sac

Air sac

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
* an anatomical structure continuous with the trachea found in some insects which can be used to actively pump air throughout the body
* an anatomical structure unique to the dinosaur and bird respiratory systems that allows unidirectional flow of air into the lungs and through the body


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  • 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 — 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 disease — noun : a serious inflammatory condition of the air sacs of poultry * * * air sac disease «AIR SAK», chronic respiratory disease in domestic fowl …   Useful english dictionary

  • 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] * * * ▪ anatomy       any of the air filled extensions… …   Universalium

  • 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 …  

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