face. It is caused by a virus. Although
mumps can infect adults, it is most com-
Scientists prepare to X-ray a 3,000-yearold
Egyptian mummy. Scientists use X-rays
to learn more about mummies without taking
apart the wrappings.
BRITANNICA STUDENT ENCYCLOPEDIA Mumps 205
mon in children between the ages of 5
and 15.
The mumps virus infects the glands
that make saliva. Any contact with the
saliva of an infected person can spread
the disease. Also, an infected person can
spread the virus into the air by
coughing or sneezing. Another person
who breathes that air can get the
disease.
The first symptoms, or signs, of mumps
may be a runny nose and a low fever.
These symptoms usually do not appear
until two to three weeks after the person
is infected. Soon the area in front of
each ear becomes swollen and puffy. The
swelling can spread to the upper neck
and jaw. In some cases mumps leads to
swelling of the brain.
Mumps needs no special treatment. The
symptoms start to go away after four or
five days. Because mumps spreads easily,
infected people should stay home. They
should also get plenty of rest.
A person who has been infected with
mumps usually develops immunity to
the disease. This means that the person
will not get mumps again. Children are
often given a shot of a substance called a
vaccine to keep them from getting the
disease.
..More to explore
Vaccine • Virus
Muscat
Population
(2007
estimate), city,
28,987; urban
area, 785,515
Muscat is the capital of Oman, a country
in the Middle East. The city is partly
surrounded by mountains. It has a natural
harbor on the Gulf of Oman.
Mumps causes the glands near the ears to
swell.
Muscat, the capital city of Oman, is located
on the Gulf of Oman.
206 Muscat BRITANNICA STUDENT ENCYCLOPEDIA
Oman’s largest oil company has its
headquarters in Muscat. A stock
exchange was opened in the city in
1989. Just outside Muscat are Oman’s
main centers of trade (Matrah) and business
(Ruwi).
In ancient times Muscat was under
Persian rule. It became an important
trading port. Portugal controlled the
city from 1508 to 1650. The
Portuguese established a trading post
and naval base there. Two Portuguese
forts from the 1500s still overlook
Muscat. Persians again ruled the city
from the mid-1600s to the mid-1700s.
The family that rules Oman today then
took over the area. The family made
Muscat its capital.
#More to explore
Oman
Muscle
Muscles make it possible for animals to
move.Worms move by tightening and
relaxing their muscles in waves. Snails
and clams crawl with the help of a big
muscle called a foot. Insects move their
legs and wings with muscles hidden
under their exoskeleton, or hard covering.
Fish, reptiles, birds, and mammals
move with the help of muscles connected
to their skeleton.
Muscle connected to a skeleton is called
skeletal muscle. Animals with backbones,
including humans, also have two
other types of muscle: cardiac muscle
and smooth muscle. Cardiac muscle
Muscles help animals move.
BRITANNICA STUDENT ENCYCLOPEDIA Muscle 207
makes blood flow. Smooth muscle helps
to digest food.
Skeletal Muscle
Skeletal muscle lies under the skin. It
is made up of long threads, or fibers.
Skeletal muscle controls movement,
posture (position of the body), and
balance. A person can move skeletal
muscle just by thinking about it and
then doing it.
Cordlike structures called tendons connect
skeletal muscle to the skeleton. As
skeletal muscle tightens, or contracts, it
gets shorter. It pulls on the bones
attached to it. As the muscle relaxes, it
gets longer. It lets the bones fall back
into place. In this way skeletal muscle
makes the bones move the parts of the
body.
To make skeletal muscle move, the brain
sends a message along a type of nerve
called a motor nerve. Motor nerves end
in the fibers of the muscle. There the
nerves release chemicals that start a wave
of electrical and chemical activity. This
activity creates energy that moves the
muscle.
Skeletal muscle makes bones move parts of the body.
208 Muscle BRITANNICA STUDENT ENCYCLOPEDIA
Some of the energy also goes into the
body as heat. This means that muscle
movement helps to keep the body at the
right temperature.
Cardiac Muscle
Cardiac muscle is located in the heart.
The fibers of this muscle form a structure
like a net. The fibers form the
chambers, or hollow areas, of the heart.
As the cardiac muscle contracts and
relaxes, blood moves in and out of the
chambers.
Cardiac muscle is involuntary muscle,
which means that it moves automatically.
A person does not have to think
about telling the heart to beat. The cardiac
muscle does not have nerves to tell
it to move, either. A special strip of cardiac
muscle releases bursts of electricity
that help the heart to beat in a regular
rhythm.
Smooth Muscle
Smooth muscle helps to move food
through the digestive system. It lines the
intestines and the stomach. Smooth
muscle also moves the diaphragm, which
helps with breathing. Smooth muscle
makes blood vessels tighten and relax,
too. Like cardiac muscle, smooth muscle
is involuntary muscle. The nervous system
and body chemicals control the
actions of smooth muscle.
Problems with Muscles
