MUSCULAR SYSTEM
Chapter 9
Joe Pistack MS/Ed
MUSCULAR SYSTEM

The word muscle comes from the Latin
word muse, which means little mouse.

When a muscle contracts, the muscle
movement under the skin resembles the
movement of the mice scurrying around.
TYPES OF MUSCLES
Three types of
muscle:
Skeletal
Smooth
cardiac
SKELETAL MUSCLE
-Generally attached to
bone.
-Voluntary musclecontrolled by choice.
-Skeletal muscle cells
are long, shaped like
cylinders or tubes.
-Appearance is striped
or striated.
SKELETAL MUSCLE
Functions:
 Produce movement.
 Maintain body posture.
 Stabilize joints.
 Produce heat-helps to maintain body
temperature.

SMOOTH MUSCLE
Generally found in the
walls of the viscera.
 Found in the
bronchioles and blood
vessels.
 Involuntary-functions
automatically.
 Does not appear striped
or striated. (nonstriated)

CARDIAC MUSCLE
Cardiac Muscle-found only in the heart.
 Function-pumps blood throughout the
body.
 Cardiac muscle is made of long branching
cells that fit together tightly at junctions
called intercalated discs. These discs
promote the rapid conduction of
electrical signals throughout the heart.

LAYERS OF CONNECTIVE TISSUE
Fascia-layers of tough
connective tissue that
surround large skeletal
muscle.
 Epimysium-the outer
layer of the fascia.
 Tendon-strong cordlike
structure that extends
toward and attaches to
the bone.

LAYERS OF CONNECTIVE TISSUE
Perimysium-another
layer of connective
tissue, surrounds smaller
bundles of muscle fibers.
 Fascicles-bundles of
muscle fibers.
 Endomysium-third level
of connective tissue the
surround the individual
muscle fibers.

LAYERS OF CONNECTIVE TISSUE
COMPARTMENT SYNDROME

Compartment syndrome or crush
syndrome, usually occurs from a crushing
injury.
◦ Ex. Pinned between two automobiles.
Usually occurs in the lower extremities.
 A normal limb has an extensive amount of
fascia that separates the muscle into
isolated compartments.

COMPARTMENT SYNDROME
Each compartment receives the blood
vessels and nerves necessary for muscle
function.
 In a “crush injury” the muscle is damaged,
it becomes red and inflamed and leaks
into the compartment.
 Pressure in the compartment increases
and compresses the nerves and blood
vessels.

COMPRESSION SYNDROME
The muscles and
nerves begin to die
due to lack of oxygen
and nourishment.
 Immediate treatment
involves reduction of
the compartment
pressure by slicing the
fascia lengthwise.

COMPARTMENT SYNDROME
MUSCLE ATTACHMENT
Muscles attach to other
structures in three ways:
 (1)tendon attaches the
muscle to the bone.
 (2)muscle attaches
directly to the bone.
 (3)sheet like fascia called
aponeurosis connects
muscle to muscle or muscle
to bone.

STRUCTURE AND FUNCTION
Actin and Myosin are two proteins that
are necessary for the contraction of
muscles.
 Sarcomere-contractile unit made up of
myofibrils.
 Muscles can only pull, not push.
 When a muscle contracts it shortens.

HOW MUSCLES CONTRACT
Sliding filament theory-the interaction of
actin and myosin sliding past each other
causing the muscles to contract.
 ATP and calcium play an important role in
the contraction and relaxation of muscles.

SOMATIC MOTOR NEURON
Motor or somatic nerve-nerve that
supplies skeletal muscle so that muscle
contraction can take place.
 A motor nerve comes from the spinal
cord and supplies several muscle fibers
with nerve stimulation.
 Neuromuscular junction (NMJ)-area
where the motor nerve meets the
muscle.

MUSCLE STIMULATION

Electrical signal is given muscle membrane.

Triggers a series of events.

Results in muscle contraction.
DISORDERS OF NMJ
Myasthenia Gravis-disease that attacks
the neuromuscular junction.
 Symptoms-are due to damaged receptor
sites on the muscle membrane.
 Muscle contraction is impaired and the
person experiences extreme weakness.
 As the disease progresses, the person
experiences difficulty breathing since
breathing muscles are skeletal muscles.

MYASTHENIA GRAVIS
TETANUS



Neurotoxins are
transmitted by certain
bacteria.
Clostridium tetani
secretes a neurotoxin
that causes excessive
firing of the motor
nerves.
Results in severs muscle
spasm and tetanic
contractions.
RESPONSE OF WHOLE MUSCLE
Single muscle fiber-contracts in an all-ornothing response.
 Whole muscle-capable of contracting
partially, can contract weakly or very
strong.

◦ Ex. Small force is necessary to lift a pencil,
greater force is necessary for 100lb. Weight.
RESPONSE OF A WHOLE MUSCLE
Recruitment-the process of recruiting
additional fibers to achieve a greater
muscle force.
 Twitch-muscle contracts and then fully
relaxes in response to a stimulus.
 Tetanus-if a muscle is stimulated
immediately and has no time to relax it
remains contracted. Sustained muscle
contraction is called tetanus.

MUSCLE TONE

Tetanic muscle contractions play an
important role in maintaining posture.

The muscle being able to tetanize gives us
an upright posture.
TONUS

Tonus-the normal continuous state of
partial muscle contraction.

Muscle tone in the smooth muscle of the
blood vessels helps to maintain blood
pressure.
ENERGY SOURCE

Muscle contraction requires a rich source
of ATP for energy, it is consumed by
contracting muscles and replaced by:
(1)Aerobic metabolism
 (2)Anaerobic metabolism
 (3)Metabolism of creatine phosphate

ORIGIN AND INSERTION

Origin-attachment
of the muscle to a
stationary bone.

Insertion-attaches
to a movable bone.
MUSCLE TERMS

Prime Mover-”chief muscle”, a single
muscle that is generally responsible for
most of the movement.

Synergists-”helper muscle”, works with
other muscles.

Antagonists-muscles that oppose the
action of other muscles.
MUSCLE TERMS

Hypertrophyoveruse of a muscle,
the muscles
increase in size.
ATROPHY

Atrophy-wasting
away or decrease
in the size of a
muscle, due to
lack of exercise
or use.
CONTRACTURE
Contractureabnormal formation
of fibrous tissue
within the muscle.
 Result of the
muscle being
immobilized for
long periods of
time.

HOW MUSCLES ARE NAMED
The names of skeletal muscles are
generally based on one or more of the
following:
 (1) size
(5)number of origins
 (2)Shape
(6)origin & insertion
 (3)direction of fibers (7)muscle action
 (4)location

Muscles of the Head
Grouped into 2 categories:
 (1) facial muscles
 (2)chewing muscles

When facial muscles contract, they pull on
the soft tissue.
 This muscular activity is responsible for
smiling and frowning.

Frontalis Muscle




Flat muscle-covers the
frontal bone.
Extends from the
cranial aponeurosis to
the skin of the
eyebrows.
Contraction of this
muscle raises your
eyebrows.
Gives us surprised
look and wrinkles your
forehead.
Orbicularis Oculi
Sphincter muscle
that encircles the
eye.
 Sphincter-ring shaped
muscle that controls
the size of an
opening.
 Contraction of the
muscle closes the eye
and assists with
winking, blinking and
squinting.

Orbicularis Oculi
Orbicularis Oris
Sphincter muscle
that encircles the
mouth.
 Contraction of this
muscle assists in
closing the mouth,
forming words, and
pursing lips.
 Kissing Muscle

Kissing Muscle
Buccinator



Inserts into the
orbicularis oris and
flattens the cheek
when contracted.
Used in whistling and
playing the trumpet.
Considered the
chewing muscle, on
contraction it helps
position food between
the teeth for chewing.
The Buccinator
The Zygomaticus

The smiling muscle.

Extends from the
corners of the
mouth to the
cheekbones.
The Smiling Muscle
Chewing Muscles

Also called muscles of
mastication(chewing).

Inserted on the mandible, or lower jaw
bone.

Considered to be some of the strongest
muscles in the body.
Masseter
Extends from the
Zygomatic Process
to the temporal
bone in the skull to
the mandible.
 Contraction of this
muscle closes the
jaw.
 Synergistically works
with the other
chewing muscles.

Temporalis

Fan-shaped muscle
that extends from
the flat portion of
the temporal bone
to the mandible.

Works synergistically
with other chewing
muscles.
The Temporalis
Sternocleidomastoid

Contraction of only one of the
sternocleidomastoid muscles causes the
head to rotate toward the opposite
direction.

Torticollis or wryneck is a spasm of this
muscle.

Characterized by twisting of the neck and
rotation of the head to one side.
Sternocleidomastoid

Extends from the sternum and clavicle to
the mastoid process of the temporal
bone in the skull.

Contraction of both muscles on either
side of the neck causes flexion of the
head.

The head bows as in prayer, called the
Praying Muscle.
Sternocleidomastoid
Trapezius

Origin is at the
base of the
occipital bone in
the skull and to
the spine of the
upper vertebral
column.
Trapezius

Origin is at the base of the occipital bone in
the skull and to the spine of the upper
vertebral column.

Contraction of the trapezius allows the head
to tilt back so that the face looks at the sky.

Works antagonistically with the
sternocleidomastoid muscle, which flexes
and bows the head. Also attached to and
moves the shoulder.
Trapezius Muscle
Muscles of the Trunk
Functions of the trunk muscles:

Involved in breathing.

Form the abdominal wall.

Move the vertebral column.

Form the pelvic region
Muscles Involved In Breathing

Intercostal muscles –
located between the
ribs and are
responsible for raising
and lowering the rib
cage during breathing.

External and Internal
Intercostals musclesare attached to the rib
cage.
Diaphragm

Dome-shaped muscle that
separates the thoracic
cavity from the abdominal
cavity.

Chief muscle of inhalation.

Breathing cannot occur
without the contraction
and relaxation of the
intercostal muscles and
the diaphragm.
Muscles That Form The Abdominal
Wall

The abdominal wall consists of four muscles
in an arrangement that provides
considerable strength.

Muscles are layered so that the fibers of
each of the four muscles run in four different
directions.

The arrangement enables the muscles to
contain, support, and protect abdominal
organs.
Muscles of The Abdominal Wall

The abdominal muscles also cause flexion of
the vertebral column and compression of
the abdominal organs during urination,
defecation, and childbirth.

The four abdominal muscles include:
Rectus abdominis
External oblique
Internal oblique
Transverse abdominis




Rectus Abdominus

Fibers run up-anddown or longitudinal
direction.

Extends from the
sternum to the pubic
bone.

Contraction of this
muscle flexes, or bends
the vertebral column.
External Oblique

Make up the lateral
walls of the
abdomen.

The fibers run
obliquely or slanted.
Internal Oblique

Part of the lateral
walls of the
abdomen.

Adds to the strength
provided by the
external oblique
muscles, as fibers of
the oblique muscles
form a crisscross
pattern.
Transverse Abdominis

Form the innermost
layer of the
abdominal muscles.

The fibers run
horizontally across
the abdomen.
Abdominal Muscles

Linea alba – white
line, an aponeurosis
of the abdominal
muscles on the
opposite sides of the
midline.

Extends from the
sternum to the pubic
bone.
Muscles of the Shoulder and Upper
Arm
Trapezius – attaches to
the base of the occipital
bone, thoracic vertebrae,
and scapula.
 When contracted, shrugs
shoulders.
 Gets its name because
the right and left
trapezius form the shape
of a trapezoid.

Trapezius Muscle
Serratus Anterior

Located on the sides
of the chest and
extends from the
ribs to the scapula.

Has a jagged shape,
like the edge of a
serrated knife.
Serratus Anterior
When the serratus
anterior contracts,
the shoulders are
lowered and the
upper arm moves
forward as if pushing
a shopping cart.
 The trapezius and
the serratus anterior
attach the scapula to
the axial skeleton.

Pectoralis Major
Large, broad muscle
that helps to form
the anterior chest
wall.
 Connects the
humerus with the
clavicle and
structures in the
anterior chest.

Pectoralis Major

Contraction of the
pectoralis major
moves the upper arm
across the front of
the chest as in
pointing to an object
in front of you.
Latissimus Dorsi

Large, broad muscle
located in the middle
and lower back
region.

Extends from the
back structures to
the humerus.
Latissimus Dorsi

Contraction of the
latissimus dorsi
muscle lowers the
shoulders and brings
the arm back as in
pointing to an object
behind you as in
swimming or rowing.
The Deltoid

Forms the rounded
portion of your
shoulder; your
shoulder pad.

Extends from the
clavicle and scapula
to the humerus.
The Deltoid

Contraction of the
deltoid muscle abducts
the arm, raising it to a
horizontal position, the
scarecrow position.

Common site of
intramuscular
injections.
Rotator Cuff Muscles

Group of 4 muscles that attach the
humerus to the scapula. These muscles
make up the Rotator Cuff

They include:
(1) Subscapularis
(2) Supraspinatus
(3) Infraspinatus
(4) Teres Minor
Rotator Cuff Muscles

The tendons of these four muscles form a
cap or a cuff over the proximal humerus,
this stabilizes the joint capsule.

The rotator cuff muscles help to rotate
the arm at the shoulder joint.
Rotator Cuff Muscles
Rotator cuff injury or impingement
syndrome is caused by repetitive
overhead motions, common in athletes
and causes shoulder pain.
 The tendons are pinched and become
inflamed resulting in pain.
 If the condition continues the inflamed
tendon can degenerate and separate from
the bone.

Rotator Cuff Muscles
Muscles That Move The Lower Arm

Triceps brachii – lies
along the posterior
surface of the
humerus.

The origin is the
scapula and the
insertion is the
olecranon of the
ulna.
Triceps Brachii
The triceps brachii is
the muscle that
supports the weight
of the body when a
person does a pushup or walks with
crutches.
 Muscle that packs
the greatest punch
for a boxer, called the
boxer’s muscle.

Biceps Brachii

Located along the
anterior surface of
the humerus.

Origin is the scapula
and the insertion is
the radius of the
forearm.
Brachialis and Brachiordialis

Act synergistically
with biceps brachii to
flex the forearm.

The biceps brachii
and the brachialis are
the prime movers for
flexion of the
forearm.
Biceps Brachii

Biceps brachii is
the muscle that is
most visible when
someone is asked
to “make a
muscle”.
Muscles That Move The Hands and
Fingers

More than 20 muscles move the hands
and fingers.

Enable the hands and fingers to perform
delicate movements.

The muscles are generally located along
the forearms.
Muscles That Move The Hands and
Fingers
Flexors are located on the anterior
surface.
 Extensors are located on the posterior
surface.
 Tendons of these muscles pass through
the wrist into the hand.
 Contraction of the muscles in the
forearm pull on the tendons thereby
moving the fingers. (like puppet strings)

Carpal Tunnel

The flexor tendons in the carpal tunnel
(wrist area), are encased in tendon
sheaths and normally slide back forth
easily.

Repetitive motion of the hand and fingers
can cause the tissues within the carpal
tunnel to become inflamed and swollen.
Carpal Tunnel

The swelling puts pressure on the median
nerve, which is located in the carpal
tunnel.

The irritated nerve causes tingling,
weakness, and pain in the hand. Pain may
radiate to arm and shoulder.

This is called carpal tunnel syndrome.
Carpal Tunnel Syndrome
Gluteal Muscles

Located on the posterior surface:

The gluteal muscles include:
(1) Gluteus Maximus
(2) Gluteus Medius
(3) Gluteus Minimus
Gluteus Maximus
Largest muscle in the
body.
 Forms the area of
the buttocks.
 Muscle that you sit
on.
 Straightens or
extends the thigh at
the hip as you climb
the stairs.

Gluteus Medius

Lies partly
behind and
superior to
the gluteus
maximus.
Gluteus Muscles
Iliopsoas

Located on the
anterior surface of
the groin.

Contraction of this
muscle flexes the
thigh, making it
antagonistic to the
gluteus maximus.
Adductor Muscles
Located on the inner
surface of the thigh.
 Adducts the thighs
by pressing them
together. (muscles
that hoarse riders
use to stay on horse)
 Include: adductor
longus, adductor
brevis, adductor
magnus, and gracilis.

Quadraceps Femoris
Most powerful muscle in the body.
 Located on the anterior thigh and is the
prime mover of knee extension.
 Contains 4 heads (points of attachment):
(1) Vastas lateralis
(2) Vastas intermedius
(3) Vastas Medialis
(4) Rectus Femoris

Quadriceps Femoris

The quads straighten
or extend the leg at
the knee as in “kicking
a football”.

Flexes the thigh at the
hip joint.

Vastas lateralis is used
as an IM injection site.
Sartorius

Longest muscle in the
body.

Strap like muscle located
on the anterior surface
of the thigh.

Allows the leg to rotate
so that you can sit
crossed-leg.
Hamstring Muscles

Group of muscles located on the
posterior surface of the thigh.

All muscles extend from the ischium to
the tibia.

Flex the leg at the knee, antagonistic to
the quadriceps femoris.
Hamstring Muscles

Strong tendon of these muscles can be
felt behind the knee.

Popliteal fossa –where the tendons form a
pit behind the knee.

Hamstring muscles include: biceps femoris,
semimembranosus, semitendinosus.
The Hamstring Muscles
Tibialis Anterior

Located on the
anterior surface,
causes
dorsiflexion of the
foot.
Peroneus Longus

Located on the
lateral surface,
everts the foot
(turns outward).
Supports the arch
of the foot and
assists in plantar
flexion.
Gastrocnemius and Soleus
Major muscles on the
posterior surface of
the leg and form the
calf of the leg.
 Contraction of these
muscles causes
plantar flexion.
 Aids in walking and
allows us to stand on
tiptoe, called the
dancer’s muscle.

Disorders Of The Muscular System

Fibromyositis – also called a charley horse.
Pain and tenderness in the fibromuscular
tissue of the thighs usually due to muscle
strain or tear.

Cramp – a painful, involuntary skeletal
muscle contraction.

Flatfoot – abnormal flatness in the sole and
arch of the foot.
Disorders Of The Muscular System

Frozen shoulder - shoulder becomes stiff
and painful making normal movement
difficult. Often caused by disuse of the
shoulder due to injury or pain associated
with bursitis.

Hypertonia – increased muscle tone
causing spasticity or rigidity.
Disorders Of The Muscular System
Hypotonia – decrease in or absence of
muscle tone, causing loose, flaccid
muscles.
 Myalgia – pain or tenderness in the
muscle.
 Myopathy – any disease of the muscles,
not associated with the nervous system.
Characterized by muscular degeneration.
