


Carbon-dioxide-rich blood is pumped from the rest of the body into the alveolar blood vessels where, through diffusion, it releases its carbon dioxide and absorbs oxygen. The alveolar membrane is the gas-exchange surface.The pulmonary alveoli are the terminal ends of the respiratory tree that outcrop from either alveolar sacs or alveolar ducts both are sites of gas exchange.An alveolus is an anatomical structure that has the form of a hollow cavity and is found in the lung parenchyma ( tissue inside the lung).
