Alveolar macrophages — white blood cells that are part of the immune system and found in the alveoli or ‘air sacs’ of the lungs — remove dust and microorganisms from the airways.

a: Gross anatomy of lung and thorax. b: Microscopic anatomy of bronchial wall. C: View of terminal airway and alveoli. d: Alveolar structure.

The lungs consist of thin-walled air sacs called alveoli. Gas exchange occurs between alveolar air and capillaries within ...