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, thus allowing room 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
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. Others, such as bronchitis and pneumonia, affect the lower respiratory
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
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 or weakened immune systems.
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 is a contagious bacterial infection
of the lungs. It continues to be a problem for people living in developing countries.