The cone-shaped lungs are sponge-like organs that fill the
chest cavity and make up most of the lower respiratory tract. Their most
important job is providing oxygen to capillaries so they can oxygenate blood.
Each lung is divided into lobes. The right lung has three, but the left lung has only two to
accommodate the heart.
Together, the lungs’ tissue surface is almost 40 times
greater than the body’s outer surface, making the lungs (together) one of the
largest organs in the body.
Each lung houses a bronchial
tree, which gets its name from the intricate network of air passages that
supply the lungs with air. The air-filled sacs in the lungs called alveoli resemble grape clusters. White
blood cells known as macrophages, located inside each alveolus, ingest and
destroy airborne irritants that enter the lungs. After you exhale, the lungs
stay partly inflated because of a fluid called surfactant that is produced by
special cells and secreted within the alveoli. Surfactant contains fatty
proteins and helps to prevent lung infections.
Suffering from a respiratory disorder is one of the most
common reasons for doctor visits in industrialized countries, where the air is
filled with chemicals, pollutants, dust, pollen, bacteria, and viruses. The
billions of microorganisms — bacteria, viruses, and fungi — in the air you
breathe can enter the lungs, and they make respiratory infections quite common.
Some infections, such as the common cold or sinusitis, affect the upper
respiratory tract, and others, such as bronchitis and pneumonia, affect the
lower respiratory tract.
Some respiratory disorders are:
- Acute bronchitis: This develops suddenly and can
occur as a complication of an upper respiratory tract infection, such as a
common cold, usually caused by a virus.
- Lung cancer: Lung cancer, a smoking-related illness,
remains a leading cause of death among adults.
- Pneumonia: Pneumonia causes the smallest parts of the
lungs (bronchioles and alveolar tissue) to become inflamed. Pneumonia can be
fatal for elderly people, children, and others with lowered immune systems.
- Asthma: Asthma attacks are caused by constricted
airways. Allergic asthma—a type caused by allergens—often develops in
childhood. The number of cases of childhood asthma continues to rise.
- Tuberculosis: Tuberculosis is a contagious bacterial
infection of the lungs. It continues to be a problem for people living in