Fundamentals of Anatomy and Physiology

The Muscular System 209

health Alert

Strong Muscles

In order to maintain healthy and strong

muscles, it is necessary to exercise them by

stretching on a daily basis. After a good night’s

sleep, get out of bed and stretch. Start slowly

moving your arms and legs; walk to an area

where there is fresh air and take deep breaths,

stretching your breath-ing muscles and filling

your lungs to ca-pacity. This action can set

your routine of moving and stretching muscles

through normal, daily activities. Walking is one

of the best exercises to maintain healthy mus-

cles. Remain relaxed when stretching, start

slowly to warm up the muscles, and then

move to a more rigorous pace. Even when

running or lifting weights, try to remain in a

relaxed mode because tension puts excessive

in the heart’s inability to pump the blood properly and can
result in death.

The Naming and Actions of

Skeletal Muscles

Muscles can be named according to their action (adductor,-
flexor, extensor), shape (quadratus, trapezius),- origin and
insertion (sternocleidomastoid), -location (e.g., frontalis,
tibialis, radialis), number of divisions (e.g., biceps, triceps,
quadriceps), and, finally, direction their fibers run
(transverse, oblique). Some muscles are named based on a
combination of the above categories, for example,- flexor
digitorum longus is named based on function, plus location,
and plus size.
The more fixed attachment of a muscle that serves as a
basis for the action is the origin. The movable at-tachment,
where the effects of contraction are seen, is called the
insertion. The origin is the proximal (closer to the axial
skeleton) attachment of the muscle to a bone; the insertion
is the distal (farthest away from the axial skeleton)
attachment to the other bone. Most voluntary or skeletal
muscles do not insert directly to a bone, but

strain on muscles and can cause damage to

muscular tissue.

As children grow, instill in them the im-

portance of exercise to maintain both healthy

muscles and bones. Regular exercising should

become part of our regular daily routines

throughout life. Even older adults should be

encouraged to take daily walks. Have you ever

noticed the older “mall walkers” early in the

morning before the stores open? Individ-uals

who are confined to bed for periods of time

should be realigned in body positions a

number of times a day to allow stretching of

muscles that normally would not be worked.

Daily exercise, like walking or more rigorous

jogging or weight lifting, will help maintain a

healthy muscular system.

rather they insert through a strong, tough, nonelastic, white

collagenous fibrous cord known as a tendon. Ten-dons vary

in their lengths from a fraction of an inch to those more

than a foot in length, like the Achilles ten-don in the lower

leg, which inserts on the heel bone. If a tendon is wide and

flat, it is called an aponeurosis (ap-oh-noo-ROH-sis).

Muscles are found in many shapes and sizes. Mus-cles

that bend a limb at a joint are called flexors. Mus-cles that

straighten a limb at a joint are called extensors. If a limb is

moved away from the midline, an abductor is functioning;

however, if the limb is brought in toward the midline, an

adductor is functioning. The muscles rotating an involved

limb are rotators. In movements of the ankle, muscles of

dorsiflexion turn the foot upward, and muscles of plantar

flexion bring the foot toward the ground. In movements of

the hand, turning the forearm when it is extended out so

that the palm of the hand faces the ground is pronation,

whereas turning the forearm so that the palm faces upward

is supination. Levators raise a part of the body, and

depressors lower a part of the body. See Chapter 8 for a

review of movements possible at synovial joints.