Inhale, exhale. Animation of the alveoli in the lungs during breathing, filling with air during inhalation and emptying during exhalation. Alveoli are the site of gaseous exchange in the lungs, where oxygen is taken up by the red blood cells and carbon dioxide is released for exhalation out of the body. The wall of each alveolus is surrounded by capillaries, allowing the diffusion of oxygen into and carbon dioxide out of the blood. Credit Polymime Animation Co. / Science Photo Library http://bit