Caption:
Lung anatomy. Computer artwork of the trachea and bronchiole network of the human lungs, seen in the silhouette of a male human figure. At upper centre the trachea (windpipe) introduces air from the larynx of the throat into the respiratory system. It branches into two bronchi which enter the pair of lungs. Within the lungs the bronchi divide into an internal network of smaller and finer bronchioles. These bronchiole tubes end in tiny balloon-like air sacs called alveoli (not seen). In the alveoli gases are exchanged: inhaled oxygen enters the blood and carbon-dioxide is breathed out. For this respiration process, the lungs are inflated by movement of the diaphragm and ribs.