The lungs are part of the respiratory system, a group of organs and tissues that work together to help us breathe.
Each lung is divided into lobes. The bronchial tree running through the lungs is made up of the windpipe, bronchus, bronchi, bronchioles, and alveoli.

The main function of the lungs is the process of gas exchange called respiration. In respiration, oxygen from incoming air enters the blood and carbon dioxide, waste gas from the metabolism, leaves the blood.

The tissue of the lungs can be affected by a number of respiratory diseases, including pneumonia and lung cancer. Chronic obstructive pulmonary disease includes chronic bronchitis and emphysema, and can be related to smoking or exposure to harmful substances. A number of occupational lung diseases can be caused by substances such as coal dust, asbestos fibres, and crystalline silica dust. Diseases such as bronchitis can also affect the respiratory tract.