This picture shows the organism Pneumococci. These bacteria are usually paired (diplococci) or appear in chains. Pneumococci are typically associated with pneumonia, but may cause infection in other organs such as the brain (pneumococcal meningitis) and blood stream (pneumococcal septicemia). (Image courtesy of the Centers for Disease Control and Prevention.)

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.

Pneumonia is an inflammation of the lungs caused by an infection. Many different organisms can cause it, including bacteria, viruses, and fungi. Pneumonia is a common illness that affects millions of people each year in the United States. The symptoms of pneumonia range from very mild to very severe, even fatal. The severity depends on the type of organism causing pneumonia as well as the age and underlying health of the individual.

White nail syndrome may also be called leukonychia. Leukonychia can occur with arsenic poisoning, heart disease, renal failure, pneumonia, or hypoalbuminemia.

This is a photomicrograph of the organism that causes pneumococcal pneumonia. The bacteria are round, but join together to form chains. Frequently, these join together to form pairs and are called diplococci; the prefix di means two.

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