Chapter 10
Anatomy of the
Muscular System
1
Introduction



There are over 600 muscles in the body
Muscles make up 40-50% of our weight
Muscle helps to determine the form and contours of
our body
2
Structure of Skeletal Muscle
 Epimysium

Layer of connective tissue that surrounds the entire muscle
 Perimysium

Separates the muscle into fasicles
 Fasicle

A group of muscle fibers
 Endomysium

Surrounds an individual muscle fiber
 Tendon

Connect muscle to bone
3
Structure of Skeletal Muscle
• Sometimes muscles are connected to
each other by broad sheets of connective
tissue called aponeuroses.
4
6
Types of Fiber Arrangements
• Parallel Fibers- run across
• Convergent- converge to a narrow
attachment
• Oblique- diagonal
– Pennate- one feather
– Bipennate- two feathers
• Direction of fibers important for strength
and range of motion
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Fiber Arrangements
 Skeletal Muscle Actions
A.
Origin and Insertion
1.
The immovable end of a
muscle is the origin, while the
movable end is the insertion;
contraction pulls the insertion
toward the origin.
2.
Some muscles have more
than one insertion or origin.
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Muscle Actions
• Prime mover- primary muscle being
moved
• Antagonist- muscles that oppose the prime
movers
• Synergist- (Syn= together Erg= work)
muscles that contract along with the prime
mover
• Fixator Muscles- joint stabilizers
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How Muscles Are Named
• Direction of Muscle Fibers
– Rectus- parallel to midline
• Location
– Temporalis near Temporal Bone
• Number of Origins
– Bicep or Tricep
• Point of Attachment
– Sternocleidomastoid muscle
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How Muscles are Named
• Function
– Adductor
– Abductor
– Flexor
– Exensor
• Shape
– Deltoid (triangular)
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How Muscles Are Named
• Size
– Maximus
– Medius
– Minimus
– Longus
– Brevis
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Head and Neck Muscles
• Two Large Categories
– Facial Muscles
• Unique because at least one of their attachments
is to the deep layers of the skin
• Allows for facial expression
– Chewing Muscles
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Facial Muscles
• Frontalis
– Covers frontal bone
– Raise eyebrows and wrinkle forehead
• Occipitalis
– Covers the posterior aspect of the skull and
pulls the scalp back posteriorly
• Epicranial Aponeurosis
– connects the Frontalis and Occipitalis
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Facial Muscles
• Obicularis Oris
– Circular muscles of the lips
– Closes the mouth
– Protrudes the lips
– Called the kissing muscle
• Obicularis Oculi
– Circular muscle around the eyes
– Allows you to close your eyes, squint, blink
and wink
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Facial Muscles
• Buccinator
– Flattens the cheek to whistle or blow trumpet
– Also a chewing muscle
• Zygomaticus
– Smiling muscle that raises the corners of the
mouth upwards
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21
Chewing Muscles
• Called muscles of mastication
• Buccinator belongs in this group
• Masseter
– Closes jaw
• Temporalis
– Lies over the temporal bone
– Inserts into the mandible and acts as a
synergist of the masseter in closing the jaw
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Neck Muscles
• Platysma
– Covers the neck anterolateral
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Neck Muscles
• Sternocleidomastoid Muscle
– Two heads of origin
• Sternum and clavicle
– Inserts in the
mastoid process
of temporal bone
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Neck Muscles
• Sternocleidomastoid Muscle
– Both flex (angle is decreased) causes bowing
of head
• Called the prayer muscles
– If only one is flexed, the head turns to the side
• In some difficult births, muscle can be
injured and spasms develop
– Called torticollis or wryneck
26
Trunk Muscles
• Anterior Muscles
– Pectoralis Major
• Large fan muscle of the chest
• Origin- from the sternum, shoulder girdle, and first
six ribs
• Inserts proximal end of the humerus
• Adducts and flexes the arm
– Pectoralis Minor
• Under the pectoralis major
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Anterior Trunk Muscles
• Intercostal Muscles
– Found between the ribs
• External Intercostals
– Elevates the rib cage for breathing
• Internal Intercostals
– Depresses the rib cage for breathing
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Anterior Trunk Muscles
• Diaphram
– Large flat muscle that separates the thoracic
from the abdominal cavity
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Muscles of the Abdominal Wall
• This group of muscles connects the rib
cage and vertebral column to the pelvic
girdle
• A band of tough connective tissue, the
linea alba, extending from the xiphoid
process to the symphysis pubis, serves as
an attachment for certain abdominal wall
muscles
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Muscles of Abdominal Wall
•Rectus Abdominus
•Outer layer
•Runs from pubis to
rib cage
•Flexes vertebral
column
•Compresses
abdominal cavity
Muscles of the Abdominal Wall
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Muscles of Abdominal Wall
• External Oblique
– Make up the lateral walls of the abdomen
– Flex the vertebrae
– Rotates the trunk
– Bend the trunk laterally
• Internal Obliques
– Fibers run at right angles to external oblique
• Transverse Abdominus
– Parallel fibers
Muscles of the Pelvic Floor
• Muscles of pelvic floor support the pelvic
cavity
• Diamond shaped outlet is called the
perineum
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Posterior Trunk Muscles
• Trapezius
– Diamond shaped muscle of back
– Shrug the shoulders
– Hold head up
– Adducts the arm
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Posterior Trunk Muscles
• Latissimus Dorsi
– Large flat muscle of lower back
– Originates in lower spine
– Inserts at the distal end of the humerus
– Extends and _____ the arm
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Posterior Trunk Muscles
• Erector Spinae
– Deep muscles of the back
• Longissimus
• Iliocostalis
• Spinalis
– Powerful back extensors (erectors)
– Can go into spasms and are a common
source of lower back pain
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ADD
• Picture of Erector Spinae
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Posterior Trunk Muscles
• Deltoid
– Triangle shoulder muscle
– Inserts in the deltoid tuberosity of the
humerus
– Multifunctional muscle
– Abducts the arm
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44
Muscles of the Upper Limb
• 6 muscles attach arm so
lots of movement
• 4 muscles form a cap or
cuff around shoulder
joint- rotator cuff
–
–
–
–
Infraspinatus
Supraspinatus
Subscapularis
Teres minor
Muscles That Act On The
Forearm
• Cause elbow flexion
• Biceps Brachii
– Two origins- scapula coracoid and
superglenoid tuberosity
– Inserts in the radial tuberosity
– Supinates the forearm
– “It turns the corkscrew and pulls the cork”
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Muscles That Act on the
Forearm
• Brachialis
– Lies deep to the bicep muscle and helps with
flexion
• Brachioradialis
– Weak muscle in the forearm
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Muscles That Act On The
Forearm
• Tricep Brachii
– Has three heads
– Is the prime mover of elbow extension
– Atagonist of the bicep
– Called the boxer’s muscle
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Muscles that Move The Wrist,
Hand, and Fingers
• Are located on the forearm
• Many intrinsic muscles
– 8 separate muscles serve the thumb
• As a general rule, forearm names reflect
their activities
– Flexor carpi and flexor digitorum muscles
cause flexion of wrist and fingers
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Muscles that Move the Wrist, Hand, and Fingers
1.
Movements of the hand are caused by
muscles originating from the distal
humerus, and the radius and ulna.
2.
Flexors include the flexor carpi radialis,
flexor carpi ulnaris, palmaris longus, and
flexor digitorum profundus.
3.
Extensors include the extensor carpi
radialis longus, extensor carpi radialis
brevis, extensor carpi ulnaris, and
extensor digitorum.
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Carpal Tunnel Syndrome
• Tendon sheath becomes inflamed and
puts pressure on the median nerve
• Characterized by weakness, pain, and
tingling in hand
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Carpal Tunnel
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Carpal Tunnel
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Causes of Carpal Tunnel
• Repetitive movements
– Playing piano
– Typing
– Swinging a hammer
– Meat cutters
– Quilting, cross-stitch, handicrafts
– Some factory work
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Carpal Tunnel Treatment
• Can be relieved with anti-inflammatory
injections
• Can wear braces to help
• Use specially designed keyboards
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Carpal Tunnel Treatment
• Permanent cure is surgical cutting or
removing swollen tissue pressing on nerve
• Will come back if you continue to do the
same tasks that caused it.
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Carpal Tunnel Treatment
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Muscles Of The Lower Limb
• Among the strongest muscles in the body
• Because pelvic girdle is composed of
heavy, fused bone that allow little
movement, no special group of muscles is
necessary to stabilize it
• Muscle that move leg form the flesh of the
thigh
• Muscles originating on leg move the ankle
and foot
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Muscles Causing Movement At
The Hip
• Gluteus Maximus
– Forms most of the buttocks
• Gluteus Medius
– Is a hip abductor
– Beneath the gluteus maximus
• Gluteus Minimus
– Under the gluteus medius
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Muscles Causing Movement At
The Hip
• Iliopsoas
– Formed by iliacus and psoas major
– Runs from iliac crest to insert on greater
trochanter of the femur
– Prime mover of hip flexion
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Iliopsoas
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Adductor Muscles
• Form the medial side of each thigh
• Since gravity does most of the work for
them, special exercises are usually
needed to keep them toned
– Adductor Longus
– Adductor Magnus
– gracilis
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Muscles Causing Movement At
The Knee Joint
• Hamstring Group
– Posterior Thigh Muscles
– Consists of three muscles
• Bicep femoris- lateral
• Semembraneous-medial
• Semitendinous- between these two
– Flexes the leg
– Butchers used to use their tendons to hang
hams from for smoking
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Muscles Causing Movement At
The Knee Joint
• Sartorius
– Thin straplike muscle
• Most superficial of thigh muscles
• Runs oblique across the thigh
• Called “tailor’s muscle” since it is a
synergist in the crossed-leg position
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Muscles Causing Movement At
The Knee Joint
• Quadriceps
–
–
–
–
Rectus Femoris
Vastus Lateralis
Vastus Medialis
Vastus Intermedius
• All 4 muscles insert
into the tibial
tuberosity of the
patellar ligament
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Muscles Causing Movement At
The Knee Joint
• Quadriceps act to extend the knee
powerfully
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Muscles Causing Movement At
The Ankle And Foot
• Tibialis Anterior
– Dorsiflexes and inverts the foot
– Inflammation of this muscle is the cause of
shin splints
• Extensor Digitorium Longus
– Lateral to the tibialis anterior
– Prime mover of toe extention and dorsiflexor
of the foot
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Muscles Causing Movement At
The Ankle and Foot
• Fibularis Muscles- found on lateral part of
leg
– Longus
– Brevis
– Tertius
– Plantar flexes and everts the foot
• Soleus
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Muscles Causing Movement At
The Ankle and Foot
• Gastrocnemius
– Bulging calf muscle
– Connects to the heal (calcaneus) by the
Achilles tendon
– Plantar flexes the foot
– Called the “toe dancer’s muscle”
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Intramuscular Injection
• Allows the Dr. to inject a large amount of
the drug at one time yet have it enter the
circulation gradually
• 5 ml or less- deltoid
• More than 5 ml- gluteus medius
• Vastus lateralis in children
86
Placement of Intramuscular
Injections
• Important to avoid the
sciatic nerve
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Intramuscular Injection Sites
Figure 6.18, 6.19b, d
R.I.C.E. Treatment For Injuries
• Rest
• Ice
– On for 15 min. off for 20 min.
• Compression
– Limits swelling
• Elevation
– Reduces swelling
– Should be above level of heart
• Referral
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Effect of Exercise On Muscle
• Muscle burns calories at three times the
rate of fat
– Lean body is more energetically efficient
• Aerobic or endurance exercises result in
stronger, more flexible muscles with
greater resistance to fatigue
• Resistance or isometric exercises increase
muscle size and strength
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Weight Training and Muscles
• Trapezius
• Pectorals
• Abdominals
– Rectus abdominus v. obliques
• Latissimus Dorsi
• Erector Spinae
• Deltoid
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Weight Training and Muscles
•
•
•
•
•
•
•
Rotator Cuff
Biceps
Triceps
Flexor and extensor muscles of forearm
Gluteal Muscles
Adductor Thigh Muscles
Hamstring Group
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Weight Training and Muscles
•
•
•
•
•
•
•
Rotator Cuff
Biceps
Triceps
Flexor and extensor muscles of forearm
Gluteal Muscles
Adductor Thigh Muscles
Hamstring Group
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Weight Training and Muscles
• Quadriceps
• Gastrocnemius
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Weight Training and Muscles
• Does the order of your weight training
exercises matter?
• Yes, lift major muscle groups first and then
small ones
• The small groups tire more easily and may
affect your ability to do the large groups if
they are tired.
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Anabolic Steroids
• Synthetically produced versions of male
sex hormone testosterone
• Banned by international athletic
competitions
• Advantages
– Increased muscle mass and strength
– Increased oxygen carrying capacity of blood
– Increased aggressive behavior
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Anabolic Steroids
• Complications
– Bloated faces
– Shriveled testes and infertility
– Damage to liver and liver cancer
– Increased blood cholesterol
– Increased risk of heart disease
– Roid rage
– Withdrawal symptoms similar to heroine
– Reduced production of natural testosterone
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Massage Therapy
• Lots of skill involved
• Can help recover from injuries and prevent
further problems
• Training varies greatly
• All programs require understanding of
anatomy and physiology
• Look for an accredited program of the
American Massage Therapy Association.
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