began fighting for control of the country.
The war lasted until 2002. Luanda
and the rest of the country suffered during
the long civil war.
..More to explore
Angola
Lung
Lungs are baglike organs, or body parts,
used for breathing. They are part of the
body’s respiratory system. All animals
An Angolan woman carries a
plate of fruit to sell in the streets
of Luanda.
BRITANNICA STUDENT ENCYCLOPEDIA Lung 183
that have a backbone and breathe air
have lungs. When an animal inhales
(breathes in), air filled with oxygen flows
into the lungs. When an animal exhales
(breathes out), a gas called carbon dioxide
and water vapor flow out of the
lungs.
Structure
A body has two lungs, one on each side
of the chest. The heart is located
between the lungs. The right lung has
three rounded sections called lobes. The
left lung has two lobes. The base of each
lung rests on a strong sheet of muscle
called the diaphragm. In normal breathing
the diaphragm and the muscles
between the ribs automatically tighten
and relax. This movement helps the
lungs to fill with air and to empty.
Air enters and leaves the lungs through a
series of tubes. A large, tough tube called
the trachea, or windpipe, connects the
top of the throat to two branching tubes
called bronchi. Each of these tubes leads
to a different lung. The bronchi then
divide into a web of smaller tubes called
bronchioles. The bronchioles lead to
tiny sacs called alveoli.
Jobs of the Lungs
When an animal breathes in, the oxygen
in the air passes through the walls of the
alveoli into tiny blood vessels called capillaries.
Red blood cells then pick up the
oxygen and take it to cells throughout
the body. The blood also carries wastes,
including carbon dioxide and water
vapor, back into the lungs. The lungs
send the wastes out of the body when
the animal breathes out.
The lungs also trap and get rid of harmful
substances from the air. A sticky liquid
called mucus lines the lungs and the
tubes leading to the lungs. The mucus
traps harmful substances such as pollution
and bacteria. Mucus and harmful
substances leave the lungs when an animal
coughs.
Lung Diseases
Most problems with the lungs can cause
coughing, chest pain, and trouble with
breathing. Pneumonia and tuberculosis
are serious infections of the lungs.
Emphysema and lung cancer are deadly
diseases of the lungs. Smoking is one of
the main causes of emphysema and lung
cancer.
#More to explore
Air • Blood • Cough • Respiratory
System
The lungs of
an average
person contain
more than
600 million
alveoli.
Ribs protect both lungs. The diagram shows
the inside of one lung, with the ribs cut away.
184 Lung BRITANNICA STUDENT ENCYCLOPEDIA
Lusaka
Population
(2005
estimate), urban
area,
1,260,000
Lusaka is the capital of Zambia, a country
in southern Africa. It is the largest
city in Zambia. It is also the center of
the country’s economy.
Many people in Lusaka work for the
government or businesses that provide
services. Farmers from surrounding areas
sell their crops and livestock in the city.
Factories in Lusaka make cement and
processed foods and drinks.
People have lived in the Lusaka area for
thousands of years. In the 1890s a British
company took control of the area.
Lusaka was founded in 1905 as a station
on a railway line. Great Britain made the
area into a colony in 1924. Lusaka
became the capital of the colony in
1935.
Lusaka was the center of a political
movement seeking to end British rule in
the area. In 1964 Zambia became an
independent country with Lusaka as its
capital. Since then the city has grown
rapidly.
..More to explore
Zambia
Lusitania
The Lusitania was a famous British
steamship of the early 1900s. A German
submarine sank the Lusitania in the
Atlantic Ocean duringWorldWar I.
Almost 1,200 people died, including
128 U.S. citizens. Partly because of this
attack, the United States entered World
War I in 1917.
Germany and Great Britain were
enemies inWorldWar I. The Germans
warned that they would try to sink the
Lusitania. They said that the ship carried
weapons as well as passengers. British
officials told the captain of the Lusitania
that German submarines had sunk other
ships along the Lusitania’s route. The
captain ignored the warnings.
On May 7, 1915, the Lusitania was near
the coast of Ireland when it was
attacked. A German submarine fired a
torpedo that struck the ship. The Lusitania
sank within 20 minutes. Only about
750 people survived.
The Lusitania docks at a crowded port.
BRITANNICA STUDENT ENCYCLOPEDIA Lusitania 185
The attack angered many people in the
United States. They wanted their country
to declare war on Germany. But for
two years the United States stayed out of
the war. The United States finally
entered the war in 1917. It said that
German submarine attacks were one of
the reasons for its decision.
#More to explore
Submarine •WorldWar I
Luther, Martin
The German priest and scholar Martin
Luther began the Reformation in 1517.
This movement at first sought to
change, or reform, the Roman Catholic
church. Instead it led to the establishment
of Protestantism, one of the major
branches of Christianity. The Protestant
church known as Lutheran grew out of
