The air sacs of the lungs are called __________.
Gas exchange in the lungs takes place in the tiny air sacs called alveoli in the lungs. The process of inhalation must inflate the alveoli, but it can only do so because of the presence of a surfactant fluid that coats the alveoli and lowers the surface tension of their walls.as exchange in the lungs takes place in the tiny air sacs called alveoli in the lungs. The process of inhalation must inflate the alveoli, but it can only do so because of the presence of a surfactant fluid that coats the alveoli and lowers the surface tension of their walls.