<P> The alveoli consist of an epithelial layer and an extracellular matrix surrounded by small blood vessels called capillaries . In some alveolar walls there are pores between alveoli called Pores of Kohn . The alveoli contain some collagen and elastic fibres . The elastic fibres allow the alveoli to stretch as they are filled with air during inhalation . They then spring back during exhalation in order to expel the carbon dioxide - rich air . </P>
<P> The alveoli consist of an epithelial layer and an extracellular matrix surrounded by small blood vessels called capillaries . In some alveolar walls there are pores between alveoli called Pores of Kohn . The alveoli contain some collagen and elastic fibres . The elastic fibres allow the alveoli to stretch as they are filled with air during inhalation . They then spring back during exhalation in order to expel the carbon dioxide - rich air . </P>
the walls of the alveoli are mostly made of
the walls of the alveoli are mostly made of
collagen and elastic fibres
collagen and elastic fibres