Chapter 11: The Muscular System

1
Chapter 11The Muscular System
2
The Muscular System

• Consists only of skeletal muscles
• Muscle organization affects power, range, and
  speed of muscle movement

3
Fascicles

• Muscle cells (fibers) are organized in bundles
  (fascicles)
• Classification of Skeletal Muscles
• By the way fascicles are organized
• By relationships of fascicles to tendons

4
Muscle Organization

• Groups of fibers are organized into fascicles
• Fibers in fascicle run parallel to fascicle, but
  fascicle can be arranged in 4 different shapes
  with respect to tendon
• Parallel Muscles
• Convergent Muscles
• Pennate Muscles
• - Unipennate, Bipennate, Multipennate
• Circular Muscles

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1. Parallel Muscles

• Fascicles run parallel to length of the muscle
• Most skeletal muscles are arranged this way
• Able to change length extensively
• Can move load over a great distance

Figure 111a
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Parallel Muscle Body

• The center or body of the muscle thickens when
  parallel muscle contracts
• Tension
• Depends on total number of myofibrils
• Directly relates to cross section of muscle
• 1 in.2 (6.45 cm2) of cross section develops 50 lb
  (23 kg) of tension

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2. Pennate Muscles

• Fascicles are arranged at an angle to tendon
• A. Unipennate Fascicle angled on one side of
  tendon
• B. Bipennate Tendon in middle with angled
  fascicles on either side
• C. Multipennate
• - Branched tendon with fascicles organized
  around each branch
• Pennate muscles produce more tension than
  parallel muscles but cannot move so far, less
  distance produced

1. Unipennate

B. Bipennate
C. Multipennate
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Pennate Muscles

• Unipennate
• fibers on 1 side of tendon
• e.g., extensor digitorum
• Bipennate
• fibers on both sides of tendon
• e.g., rectus femoris
• Multipennate
• tendon branches within muscle
• e.g., deltoid

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3. Convergent Muscles

• Fascicles spread out like a fan on one end and
  converge to a single point on the other
• Produce less tension and distance than parallel
  muscles but
• Independent contraction of fascicles can produce
  different movement from the same muscle
• Provides versatility
• Muscle fibers pull in different directions,
  depending on stimulation

Figure 111b
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4. Circular Muscles

• Also called sphincters
• Concentric arrangement of fascicles
• Function
• Decrease diameter of openings to guard entrances
  and exits
• e.g., obicularis oris

Figure 111f
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Why does a pennate muscle generate more tension
than does a parallel muscle of the same size?

1. Parallel fibers do not respond to calcium.
2. A pennate muscle contains more muscle fibers.
3. Muscle force is concentrated on the insertion in
   pennate muscles.
4. This is not a true statement.

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Which type of muscle would you expect to be
guarding the opening between the stomach and the
small intestine?

1. convergent muscle
2. multipennate muscle
3. parallel muscle
4. circular muscle (sphincter)

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Muscle Terminology

• Muscles have 1 fixed point of attachment (origin)
  and 1 moving point of attachment (insertion)
• Origin
• Where the fixed end of the muscle attached to
  bone, cartilage, or CT
• Origin is usually proximal to insertion
• Insertion
• Where the moveable end attaches
• Action
• The specific movement produced by the muscle
  during contraction
• e.g., flexion, extension, adduction, etc.

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Muscles interact to produce or oppose movements.
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Muscle Interactions

• Muscles work in groups to maximize efficiency
• Smaller muscles reach maximum tension first,
  followed by larger, primary muscles

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Muscle Terminology

• Muscle often work in groups to increase tension
  or fine tune movement
• Different muscles serve different function
• Agonist
• prime mover, muscle most responsible for the
  movement
• Synergist
• a muscle with the same action as the agonist
• assists agonist at the beginning of contraction
  when fiber length is not optimal for agonist
• helps start motion or stabilize origin of agonist
  (fixator)
• Antagonist
• a muscle whose action opposes the agonist
• produces the opposite action to fine tune
  movement by the agonist

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Muscle Opposition

• Agonists and antagonists work in pairs
• when 1 contracts, the other stretches
• i.e. flexorsextensors
• abductorsadductors

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The name of a muscle helps identify its location,
appearance, or function.
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Descriptive Names for Skeletal Muscles

1. Location in the body
2. Fascicle organization
3. Relative position
4. Structure, Size and Shape
5. Origin and insertion
6. Action

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Naming Muscles

• Names of muscle are derived from aspects of their
  features
• Location
• - Named for part of the body where theyre
  located
• - e.g. Brachii, Abdominis
• Fascicle Organization
• - Named for how fascicles are organized with
  respect to the body
• - e.g. Rectus straight
• Oblique angle
• Relative Position
• - Named for depth when layered
• - e.g. Externus/Superficialis top, surface
• Internus/Profundus deep

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Naming Muscles

• 4. Structure, Size and Shape
• Number of tendons
• - e.g. triceps, biceps
• Shape of Muscle
• e.g. trapezius trapezoid
• deltoid triangle
• soleus fish
• Size of muscle relative to others
• Major bigger
• Maximus biggest
• Longus long
• Vastus great

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Naming Muscles

• Origin and Insertion
• - Name of regions of attachment, origin
  first,
• insertion second
• - e.g. sternocleidomastoid
• Origin manubrium of sternum and medial
  clavicle
• Insertion mastoid process
• 6. Action
• - Named for action performed and region
• acted upon
• - e.g. extensor digitorum
• Usually multiple naming schemes are combined to
  name the muscle
• e.g. flexor carpi ulnaris
• Individual muscles, orgins, insertions and
  actions are examined in lab.

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Naming Skeletal Muscles
Table 111 (1 of 2)
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Naming Skeletal Muscles
Table 111 (2 of 2)
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Effects of Aging on the Muscular System

• Skeletal muscle fibers become smaller in diameter
• Skeletal muscles become less elastic
• develop increasing amounts of fibrous tissue
  (fibrosis)
• Decreased tolerance for exercise
• Decreased ability to recover from muscular
  injuries

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Muscle A abducts the humerus, and muscle B
adducts the humerus. What is the relationship
between these two muscles?

1. synergists
2. antagonists
3. agonists
4. fixators

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What does the name flexor carpi radialis longus
tell you about this muscle?

1. its size
2. its function
3. its location
4. 1, 2, and 3 are correct

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• A Closer Look
• at the Muscular System

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Axial and Appendicular Muscles
Figure 113a
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Axial and Appendicular Muscles
Figure 113b
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Divisions of the Muscular System

• Axial muscles
• position head and spinal column
• move rib cage
• 60 of skeletal muscles
• Appendicular muscles
• support pectoral and pelvic girdles
• support limbs
• 40 of skeletal muscles

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The Axial Muscles

• Divisions based on location and function
• muscles of head and neck
• muscles of vertebral column
• oblique and rectus muscles
• muscles of pelvic floor

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Muscles of Facial Expression
Figure 114b
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Summary Muscles of Facial Expression
Table 112 (1 of 2)
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Summary Muscles of Facial Expression
Table 112 (2 of 2)
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Anterior Muscles of the Neck
Figure 119
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Oblique and Rectus Muscles

• Lie within the body wall

Figure 1111a, b
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Functions of Oblique and Rectus Muscles

• Oblique muscles
• compress underlying structures
• rotate vertebral column
• Rectus muscles
• flex vertebral column

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Oblique Muscles

• Thoracic region
• intercostal muscles (external and internal
  intercostals)
• respiratory movements of ribs
• Abdominopelvic region (same pattern as thoracic)
• external oblique muscles
• internal oblique muscles

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Rectus Group

• Rectus abdominis
• between xiphoid process and pubic symphysis
• divided transversely by tendinous inscriptions

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Oblique Muscles
Table 119 (1 of 2)
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Oblique and Rectus Muscles
Table 119 (2 of 2)
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The structures and functions of the major
muscle groups of the upper and lower limbs.
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The Appendicular Muscles
Figure 1113b
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The Appendicular Muscles
Figure 1113a
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The Appendicular Muscles

• Position and stabilize pectoral and pelvic
  girdles
• Move upper and lower limbs
• Move the arm
• Move the forearm and hand
• Move the hand and fingers

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Muscles that Position the Pectoral Girdle
Figure 1114b
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Muscles that Position the Pectoral Girdle
Figure 1114a
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Muscles that Position the Pectoral Girdle

• Trapezius
• superficial
• covers back and neck to base of skull
• inserts on clavicles and scapular spines
• Rhomboid and levator scapulae
• deep to trapezius
• attach to cervical and thoracic vertebrae
• insert on scapular border
• Serratus anterior
• on the chest
• originates along ribs
• inserts on anterior scapular margin

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Muscles that Position the Pectoral Girdle
Tables 1111
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Muscles that Move the Arm
Figure 1115a
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Muscles that Move the Arm
Figure 1115b
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9 Muscles that Move the Arm

• Deltoid
• the major abductor (away from longitudinal axis)
• Teres major/minor
• produce rotation at shoulder
• Coracobrachialis
• attaches to scapula
• produces flexion and adduction at shoulder

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9 Muscles that Move the Arm

• Pectoralis major
• between anterior chest and greater tubercle of
  humerus
• produces flexion at shoulder joint
• Latissimus dorsi
• between thoracic vertebrae and humerus
• produces extension at shoulder joint

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The Rotator Cuff

• Muscles involved in shoulder rotation
• supraspinatus, subscapularis, infraspinatus,
  teres minor,and their tendons

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Muscles that Move the Arm
Table 1112
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Baseball pitchers sometimes suffer from rotator
cuff injuries. Which muscles are involved in
this type of injury?

1. rhomboid major and minor, teres major and minor
   muscles
2. teres major, teres minor and serratus anterior
   muscles
3. pectoralis major and minor muscles
4. supraspinatus, infraspinatus, subscapularis, and
   teres minor muscles

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Muscles that Move the Forearm and Hand
Figure 1116a
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Muscles that Move the Forearm and Hand
Figure 1116b
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Muscles that Move the Forearm and Hand

• Originate on humerus and insert on forearm
• Exceptions
• the major flexor (biceps brachii)
• mainly on anterior and medial surfaces
• the major extensor (triceps brachii)
• mainly on posterior and lateral surfaces of arm

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Muscles that Move the Forearm and Hand

• Biceps brachii
• flexes elbow
• stabilizes shoulder joint
• originates on scapula
• inserts on radial tuberosity
• Triceps brachii
• extends elbow
• originates on scapula
• inserts on olecranon
• Brachialis and brachioradialis
• flex elbow

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Muscles that Move the Forearm and Hand

• Flexor carpi ulnaris
• superficial
• flexes wrist
• adducts wrist
• Flexor carpi radialis
• superficial
• flexes wrist
• abducts wrist
• Extensor carpi radialis
• superficial
• extends wrist
• abducts wrist

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Muscles that Move the Forearm and Hand

• Extensor carpi ulnaris
• superficial
• extends wrist
• adducts wrist

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Summary Muscles that Move the Forearm and Hand
Table 1113 (1 of 2)
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Summary Muscles that Move the Forearm and Hand
Table 1113 (2 of 2)
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Muscles that Move the Hand and Fingers
Figure 1117a, b
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Muscles that Move the Hand and Fingers
Figure 1117c, d
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Summary Muscles that Move the Hand and Fingers
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Muscles of the Pelvis and Lower Limbs

• Pelvic girdle is tightly bound to axial skeleton
• permits little movement
• has few muscles

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Muscles that Position the Lower Limbs

1. Muscles that move the thigh
2. Muscles that move the leg
3. Muscles that move the foot and toes

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Muscles that Move the Thigh
Figure 1119a, b
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Muscles that Move the Thigh
Figure 1119c, d
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Muscles that Move the Thigh

• Gluteal muscles
• Lateral rotators
• Adductors
• Iliopsoas

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Muscles that Move the Thigh

• Gluteal Muscles
• Gluteus maximus
• largest, most posterior gluteal muscle
• produces extension and lateral rotation at hip
• Adductors
• Gracilis
• hip flexion and adduction

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Muscles that Move the Leg
Figure 1120a
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Muscles that Move the Leg
Figure 1120b, c
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Muscles that Move the Leg

• Flexors of the knee
• originate on the pelvic girdle
• Extensors of the knee
• originate on the femoral surface
• insert on the patella

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Flexors and Extensors of the Knee

• Flexors of the Knee
• Biceps femoris
• Semimembranosus
• Semitendinosus
• Sartorius
• originates superior to the acetabulum
• Extensors of the Knee
• 4 muscles of the quadriceps femoris
• 3 vastus muscles
• rectus femoris muscle

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Hamstrings

• Hamstrings are made up of
• biceps femoris
• semimembranosus
• semitendinosus

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Muscles that Move the Leg
Table 1117 (1 of 2)
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Muscles that Move the Leg
Table 1117 (2 of 2)
82
You often hear of athletes who suffer a pulled
hamstring. To what does this phrase refer?

1. biceps femoris, gracilis, and adductor magnus
   damage
2. rectus femoris, vastus lateralis and vastis
   medialis damage
3. semitendinosus, biceps femoris, and
   semimembranosus muscle damage
4. sartorius, gracilis and rectus femoris damage

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Muscles that Move the Foot and Toes
Figure 1121a, b
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Muscles that Move the Foot and Toes
Figure 1121c, d
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Muscles that Move the Foot and Toes

• Extrinsic muscles that move the foot and toes
  include
• muscles that produce extension at the ankle
• muscles that produce flexion at the ankle
• muscles that produce extension at the toes
• muscles that produce flexion at the toes

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Muscles that Produce Movement at the Ankle

• Muscles that Produce Extension at the Ankle
• Gastrocnemius
• Soleus
• Fibularis
• Tibialis posterior
• Muscles that Produce Flexion at the Ankle
• Tibialis anterior
• opposes the gastrocnemius

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The Achilles Tendon

• The calcaneal tendon (Achilles tendon)
• shared by the gastrocnemius and soleus

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Muscles the Produce Movement of the Toes

• Muscles that Produce Extension at the Toes
• Extensor digitorum longum
• Muscles that Produce Flexion at the Toes
• Flexor digitorum longum

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SUMMARY

• Effects of muscle structure on function
• Organization of skeletal muscle fibers
• parallel, convergent, pennate, circular
• Relationships between levers and movement
• Actions of first, second, and third class levers
• Origins and insertions of skeletal muscles
• Actions of skeletal muscles
• agonist, antagonist, synergist
• How skeletal muscles are named

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SUMMARY

• Structures and functions of axial muscles
• muscles of head and neck
• muscle of vertebral column
• oblique and rectus muscles
• muscles of pelvic floor
• Structures and functions of the appendicular
  muscles
• muscles of shoulders and upper limbs
• muscles of pelvis and lower limbs
• Effects of aging on the muscular system