UPSC CAPF AC 2020 Paper

During respiration in human beings, the actual place of gaseous exchange is alveoli. Alveoli are tiny air sacs present in our lungs, where gaseous exchange of O2 and CO2 take place between atmospheric air or alveoli air and blood of pulmonary capillaries. Alveoli are made up of single epithelial layer of simple squamous epithelium, which make diffusion of gases easily. Our lungs have about 480 million alveoli, located at the end of bronchial tubes.