What cartilage does do is that it keeps joint motion fluid by coating the surfaces of the bones in our joints and by cushioning bones against impact. It is not as rigid as bone, but is stiffer and less flexible than muscle tissue.
The smallest bronchioles end in tiny air sacs, called alveoli. They inflate when a person inhales and deflate when a person exhales. During gas exchange oxygen moves from the lungs to the bloodstream.
