Құстар мен динозаврлардың тыныс алу жүйесіндегі ауа қаптары

Part of the respiratory system of birds
a component of dinosaur and bird skeletal systems
Air sacs are spaces within an organism where there is the constant presence of air. Among modern animals, birds possess the most air sacs (9–11), with their extinct dinosaurian relatives showing a great increase in the pneumatization (presence of air) in their bones.

Birds have a system of air sacs in their ventilation system. The air sacs work to produce a unidirectional flow where air enters and exits the lung at the same rate, contrasting the lungs of other tetrapods such as mammals where air enters and exits the lung in a tidal ventilation. No gas exchange occurs within them. However, this morphology varies among bird species. Birds such as parrots have different air sac arrangements. The morphologies of the individual air sacs also vary among bird taxa. Instead, voluminous expansion occurs in the air sacs. Different air sacs alternate contraction and expansion, causing air motion, the fundamental mechanism of avian respiration. The compliance of the air sacs is related to the timing of all of the moving parts involved in respiration. Birds have hollow pneumatic bones. The hollow air spaces in bird bones outside of the head are connected to the air sacs in a way that a bird with a blocked windpipe and a bone broken in a manner where the inside of the bone was connected to the outside world could still breathe. These pneumatic bones are less vascularized than non pneumatic bones and many pneumatic bones have pneumatic foramina (openings for air passage). Bone pneumaticity is generally found in the appendicular skeleton.