Alveoli are part of lung parenchyma and can be termed as an anatomical structure that acts like an ending to one’s respiratory tree. Alveoli are basically air sacs that act as the point of formation and termination of a person’s respiratory tract. Around 700 million alveoli are present in a pair of lungs. Wrapped in capillaries, these alveoli have a surface area of around 70 square meters. While each alveolus is about 200 micrometers in diameter, its size can increase when a person inhales.
