The alveoli are tiny air pockets, which have elastic walls consisting a single, thin cell layer or epithelium which makes gaseous exchange possible. Around the alveolus is a very dense network of cappilaries which provide an excellent blood supply. The alveoli is provided with deoxygenated blood from the pulmonery artery and when the blood leaves the alveolus, it is oxygenated and is carried away to the pulmonery vein.
There are about 700 million alveoli in man's lungs witha total absorbing surface of about 70-80 square metres. The lining of alveoli is covered witha thin film of moisture, which allows the diffusion of oxygen to the blood and carbon dioxide into the alveolus.
Supported by these adaptations, alveoli carries a major role in the exhange of gases, allowing carbon dioxide to diffuse out and oxygen to diffuse into the blood. So, the role of alveoli is very important in gaseous exchange.
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