so the air can go thought it easily
The air sac must have thin walls so that air passes easily through it.
lubricated
The air in the thermosphere is very thin because of it's high altitude.
The layer of the atmosphere where the air is very thin and has little moisture is the mesosphere. This region is located above the stratosphere and below the thermosphere, and it is characterized by low temperatures and a decrease in air density.
diffusion of gases (oxygen and carbon dioxide) to & from air in lungs and capillaries in alveoli
The air is usually very thin at the top of a mountain.
Their must be a very unhappy bird flying past. Just kidding, the definition if 'thin air' implies it came into existence from nowhere, which is a bit improbable. My explanation is that it was a drop of water (rain, vapour, roof etc)
Because the higher you go the more thin air. So the engines have to work very hard to suck air in their engines dues to thin air and less air.
MacBook Air
the paouch like air secs at the smallest lenchioles is called alveoli.the walls of alveoli are very thin and they are sorrounding thin blood capllaries .it is in alveoli exchange of gaseouse takes place there are so many alveoli in blood so they provides very larges surface srea for cxchanges of gaseouse
The air at the very tip is really thin, and not enough to survive mostly.
Lung arterioles are relatively thin-walled to allow for gas exchange to occur easily. Thin walls help facilitate the diffusion of oxygen from the air sacs in the lungs into the bloodstream and carbon dioxide out of the bloodstream and into the air sacs. This design maximizes efficiency of gas exchange in the lungs.