The major features of the lungs include the bronchi, the bronchioles and the alveoli. The alveoli are the microscopic blood vessel-lined sacks in which oxygen and carbon dioxide gas are exchanged.

This x-ray shows a single lesion (pulmonary nodule) in the upper right lung (seen as a light area on the left side of the picture). The nodule has distinct borders (well-defined) and is uniform in density. Tuberculosis (TB) and other diseases can cause this type of lesion.

This CT scan shows a single lesion (pulmonary nodule) in the left lung. This nodule is seen as the light circle in the upper portion of the dark area on the left side of the picture. A normal lung would look completely black in a CT scan.

Aspergillosis is an acute pulmonary infection caused by the aspergillus fungus. Aspergillus can cause illness three ways: an allergic reaction in asthmatics; a colonization in scarred lung tissue; and an invasive infection with pneumonia which can affect the heart, lungs, brain and kidneys.

Aspergillosis is an acute pulmonary infection caused by the aspergillus fungus. Aspergillus can cause illness three ways: an allergic reaction in asthmatics; a colonization in scarred lung tissue; and an invasive infection with pneumonia which can affect the heart, lungs, brain and kidneys.

Aspergillosis is a fungal infection. The fungus invades and destroys tissue. This type of infection usually occurs in immunocompromised individuals. Here, a chest x-ray shows that the fungus has invaded the lung tissue. The lungs are usually seen as black areas on an x-ray. The cloudiness on the left side of this x-ray is caused by the fungus.

Air is breathed in through the nasal passageways, travels through the trachea and bronchi to the lungs.