Muscles make up a large portion of our body weight and help us move,
talk and eat. There are 3 types of muscles:
- voluntary muscles of the skeletal system
- involuntary smooth muscles (handle functions like digesting food,
focusing the eyes)
- involuntary cardiac muscles (heart muscle)
The 605 skeletal muscles vary in shape and strength. The muscles that
surround the spine are the most powerful. Regular exercise helps keep
our muscles in good shape. Injuries to muscles and the tendons that
attach muscle to bone are usually the result of overexertion or a sudden
pull or twist. When injured, muscles can repair themselves. Muscle
strain occurs when the muscle fibers are damaged, usually due to
constant repetition of a movement. A muscle tear occurs when a large
number of muscle fibers are torn. This causes severe pain and swelling.
Many diseases that affect muscle, such as polio, are diseases of the
nerves that are connected to muscles. This can result in weakness and
wasting away of the muscle, or a muscle twitch. Muscle diseases can be
inherited, as the result of an infection, or a side effect of
medication. These diseases include muscular dystrophy, myopathy,
myositis, lupus and vitamin deficiency.
Introduction
Muscles are very important elements of the human body. They account for
about half of a person’s weight.
Understanding how muscles work and how they can be injured is necessary
for preventing muscle injuries and recognizing symptoms of muscle
disease.
This patient education program reviews the types of muscles, how they
function, and the various injuries and diseases that can harm them.
Muscles
There are 3 types of muscles in the body.
- voluntary muscles of the skeletal system
- involuntary smooth muscles
- involuntary cardiac muscles
This program will help you understand the voluntary skeletal muscles.
The involuntary muscles handle unconscious functions such as pushing the
food along in the digestive system, focusing the eyes, and controlling
the width of arteries.
Cardiac muscles are involuntary too, but they have a special structure
and function and are only in the heart.
All muscles
- can be excited by a nerve or a stimulus
- contract when stimulated
- relax after contraction
Skeletal Muscles
About 605 skeletal muscles make up almost half the weight of the body.
Muscles work together with the skeletal system and the nervous system.
A typical skeletal muscle stretches from one bone to another, crossing a
joint. Muscles are attached to bones with tendons. Tendons are special
tissues of connective fibers.
Ligaments also connect bones. Ligaments are made of tough connective
tissue.
The brain sends messages to the muscles, telling them to move, through
the spinal cord and the spinal nerves, finally reaching the muscle.
A muscle contracts when the electrical impulse of a nerve reaches it.
Each muscle has thousands of specialized fibers, which start sliding
along each other when stimulated, causing a contraction.
As a muscle contracts, it moves one bone relative to another. Many
muscles are attached to more than 2 bones.
Muscles are arranged opposite of each other. For instance, the movement
of the triceps reverses the movement of the biceps. This way, the biceps
allow us to bend our elbow and the triceps allows us to extend it.
Anatomy
The skeletal muscles vary in shape and strength. The muscles that
surround the spine are the most powerful muscles. They give us posture.
Shoulder muscles help move our arms. For example, the deltoid muscle
allows us to move our arm away from our body.
The muscles of the front forearm allow us to make a fist and bend our
fingers. The muscles on the back of the forearm do the opposite: they
allow us to open our hand and extend our fingers.
The quadriceps muscle, the big, bulky muscle on the front of the thigh,
allows us to straighten our knee. The hamstring muscle on the back of
the thigh allows us to bend our knee.
The muscles in the shin of the leg allow us to bend our ankle upward,
while the calf muscle allows us to bend our ankle downward.
The combination of all the skeletal muscles allows us to walk, run,
write, and play!
The muscles in the face allow us to open and close our eyes and mouth.
They also allow us to make facial expressions, such as smiling and
frowning.
The tongue and cheek muscles allow us to chew and eat. The throat
muscles allow us to swallow and breathe.
Other muscles are very important but we do not notice them all the time.
These include our neck, back, chest and abdomen muscles. They help us
maintain a good posture and move the spine. They also protect the organs
in our chest and belly.
Regular exercise helps to keep our muscles in good shape.
Muscle Injuries
Muscle injuries are more frequent than muscle diseases. When injured,
muscles are capable of repairing themselves.
Injuries to muscles and tendons are usually the result of overexertion
or a sudden pull or twist.
Muscle strain is when the muscle fibers are damaged. Some bleeding
inside the muscle causes tenderness and swelling. Pain and visible
bruising accompany strain.
Muscle strains can occur due to constant repetition of a certain
movement, mainly if performed incorrectly.
Strains are usually treated with short-term immobilization and physical
therapy and anti-inflammatory drugs.
A muscle tear is when a large number of muscle fibers are torn. Muscle
tears cause severe pain and swelling. Severe bleeding may results in the
formation of a blood clot. Surgery may be necessary to repair a muscle
tear.
Inflammation of a tendon, called tendonitis, can happen when stretching
or repeated movement causes swelling of a tendon. Activities like
running and kicking can cause inflammation of tendons in the foot. This
may cause pain, swelling, and restricted movement.
When a tendon tears, damage to the tendon is so severe it separates it
from the bone. Lifting too much weight can result in tendon tears. Minor
tendon tears are treated with immobilization and physical therapy.
However, more serious tendon tears sometimes require surgery.
Muscle Diseases
Many diseases that affect muscles are actually diseases of the nerves
that are connected to the muscles. The result is weakness and wasting
away of the muscle, called atrophy.
As the muscles weaken, they may start twitching. This muscle twitching
is called fasciculation.
Here are some of the diseases that affect muscles by affecting their
nerves.
- Spinal cord injuries
- Pinched nerves in the neck or back
- Polio
- Charcot-Marie-Tooth disease.
- Lou Gehrig’s disease
Most muscle cramps are caused by nerves malfunctioning. During a cramp,
the muscle contracts by itself due to abnormal nerve signals. Muscle
cramps can be very painful. They may occur particularly after exercise
or at night. Stretching the muscle can relieve cramp pain.
Diseases that affect the muscles directly, rather than their nerve
supply, include
- Muscular dystrophy
- Myopathy
- Myositis
Muscle diseases can be inherited, the result of infections, or side
effects of medications taken for other conditions. The affected muscles
usually become weak and sometimes painful.
Other diseases of the body affect the muscles, such as lupus, thyroid
problems, and vitamin deficiencies.
Diagnosis
To diagnose muscle diseases, a very detailed personal and family history
must be taken. A physical exam is very important in assessing the
extent of weakness. It also checks for atrophy and fasciculations.
Blood and urine tests may also be needed to diagnose muscle disease.
MRIs of the affected spine or brain area, as well as the affected
muscles, may be necessary.
Needle tests called EMG for ElectroMyoGram and NCV for Nerve Conduction
Velocity may be done to determine whether the disease is primarily in
the muscles or whether it is due to nerve damage.
A small piece of muscle may need to be taken and studied by a
pathologist under a microscope. This is called a muscle biopsy. The
muscle sample is taken using either a needle or a scalpel.
Treatment
Muscle and tendon strains are usually treated with immobilization and
physical therapy. Muscle and tendon tears are treated the same way,
although surgery may be needed to fix a tear.
The treatment of muscle diseases depends on what causes the disease. If
the disease is caused by lack of vitamins, a simple vitamin supplement
may fix the problem. Weakness due to low hormone levels may be treated
with hormone replacement.
Some types of muscular dystrophy have no effective treatments. Most
treatment for serious muscle disease requires physical therapy to
strengthen the muscles.
Occupational therapy is sometimes needed if muscle weakness persists.
The patient has to learn “tricks” in order to do daily activities. For
example, the patient may use a reacher to put clothes on.
Summary
Muscles make up a large portion of the body’s weight and help us to walk, run, talk, and eat.
Keeping muscles healthy and strong is important for a healthy lifestyle.
Learning how to exercise safely and avoiding repetitive motion that can cause strain is essential to healthy living.
