Chapter 11: The Muscular System Biol 141 A

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Chapter 11The Muscular SystemBiol 141 AP
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The Muscular System

• Consists only of skeletal muscles
• How are fascicles arranged in the various types
  of muscles, and what are the resulting functional
  differences?

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Muscle Organization and Function

• Muscle organization affects power, range, and
  speed of muscle movement
• 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

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Organization of Skeletal Muscle Fibers

• 4 patterns of fascicle organization
• 1) Parallel-
• Fibers parallel to the long axis of muscle
• - e.g., biceps brachii
• 2) Convergent-
• 3) Pennate-
• 4) Circular-

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Parallel Muscles
Figure 111a
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Parallel Muscle Body

• The center or body of the muscle thickens when
  parallel muscle contracts
• Parallel muscles contract about 30
• Parallel Muscle 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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Convergent Muscles
Figure 111b
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Convergent Muscles

• A broad area converges on attachment site
  (tendon, aponeurosis, or raphe)
• Muscle fibers pull in different directions,
  depending on stimulation
• e.g., pectoralis muscles

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Pennate Muscles
Figure 111c, d, e
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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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Pennate Muscles

• Form an angle with the tendon
• Do not move as far as parallel muscles
• Contain more myofibrils than parallel muscles
• Develop more tension than parallel muscles

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Circular Muscles
Figure 111f
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Circular Muscles

• Also called sphincters
• Open and close to guard entrances of body
• e.g., obicularis oris

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Skeletal Motion

• Skeletal muscles attach to skeleton, produce
  motion
• Type of muscle attachment affects power, range,
  and speed of muscle movement

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What are the classes of levers, and how do they
make muscles more efficient?

• Levers
• Mechanically, each bone is a lever (a rigid,
  moving structure)
• and each joint a fulcrum (a fixed point)
• Muscles provide applied force (AF)
• required to overcome resistance (R)

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Functions of a Lever

• To change
• direction of an AF
• distance and speed of movement produced by an AF
• effective strength of an AF

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3 Classes of Levers

• Depend on the relationship between applied force,
  fulcrum, and resistance
• first class
• second class
• third class

First, Second, and Third-Class Levers
PLAY
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First-Class Levers
Figure 112a
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First-Class Levers

• Seesaw is an example
• Center fulcrum between applied force and
  resistance
• Force and resistance are balanced

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SecondClass Levers
Figure 112b
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Second-Class Levers

• Wheelbarrow is an example
• Center resistance between applied force and
  fulcrum
• A small force moves a large weight

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Third-Class Levers
Figure 112c
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Third-Class Levers

• Most common levers in the body
• Center applied force between resistance and
  fulcrum
• Greater force moves smaller resistance
• Maximizes speed and distance traveled

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KEY CONCEPT

• Skeletal muscles can shorten to 70 of resting
  length
• Power, speed, and range of movement
• Depend on positions of muscle attachment
• Relative to joints

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How are actions of a muscle based on the relative
positions of its origin and insertion?
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Origins and Insertions

• Muscles have 1 fixed point of attachment (origin)
  and 1 moving point of attachment (insertion)
• Most muscles originate or insert on the skeleton
• Origin is usually proximal to insertion

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Actions

• Movements produced by muscle contraction
• Body movements
• e.g., flexion, extension, adduction, etc.
• Described in terms of bone, joint, or region

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How do muscles interact to produce or oppose
movements? 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 Based on Function

• Agonist (prime mover)
• produces a particular movement
• Antagonist
• opposes movement of a particular agonist
• Synergist
• a smaller muscle that assists a larger agonist
• helps start motion or stabilize origin of agonist
  (fixator)

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Muscle Opposition

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

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How does the name of a muscle help identify its
location, appearance, or function?
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Names of Skeletal Muscles

• Correct names of muscles include the term muscle
• Exceptions
• platysma
• diaphragm

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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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Descriptive Names for Skeletal Muscles

• Location in the body-Identifies body regions
  e.g.- temporalis muscle
• Origin and insertion- First part of name
  indicates origin, Second part of name indicates
  insertion e.g. genioglossus muscle
• Fascicle organization-Describes fascicle
  orientation within muscle
• i.e., rectus (straight), transversus, oblique

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Descriptive Names for Skeletal Muscles

• 4. Relative position- Externus (superficialis)
• visible at body surface
• Internus (profundus)deep muscles
• Extrinsicmuscles outside an organ
• Intrinsicmuscles inside an organ
• 5. Structural characteristics- Number of tendons
• bi 2, tri 3
• Shape trapezius, deltoid, rhomboid
• Size-
• 6. Action- Movements e.g., flexor, extensor,
  retractor
• Occupations or habits e.g., risor laughter

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Names for Muscle Size (1 of 2)

• Longus long
• Longissimus longest
• Teres long and round
• Brevis short
• Magnus large
• Major larger
• Maximus largest
• Minor small
• Minimus smallest

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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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What are the principle axial muscles of the
body, their origins, insertions, actions, and
innervation? 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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6 Muscle Groups of the Head and Neck

• Muscles of facial expression
• originate on skull
• Extrinsic eye muscles
• originate on surface of orbit
• control position of eye

3D Peel-Away of Muscles of the Head and Neck
PLAY
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6 Muscle Groups of the Head and Neck

• Muscles of mastication
• move the mandible
• Muscles of the tongue
• names end in glossus
• Muscles of the pharynx
• begin swallowing process

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6 Muscle Groups of the Head and Neck

• Anterior muscles of the neck
• control position of larynx
• depress the mandible
• support tongue and pharynx

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Muscles of Facial Expression
Figure 114a
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Muscles of Facial Expression
Figure 114b
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Muscles of Facial Expression

• Orbicularis oris
• constricts the mouth opening
• Buccinator
• moves food around the cheeks
• Muscles of the epicranium (scalp)

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Muscles of the Epicranium (Scalp)

• Temporoparietalis
• Occipitofrontalis
• frontal and occipital bellies
• separated by epicranial aponeurosis
• Platysma
• covers anterior surface of neck

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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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Extrinsic Eye Muscles

• Also called extra-ocular muscles

Figure 115a, b
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Extrinsic Eye Muscles
Inferior rectus Medial rectus Superior
rectus Lateral rectus Inferior oblique Superior
oblique
Figure 115c
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Summary Extrinsic Eye Muscles
Table 113
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Muscles of Mastication
Figure 116
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3 Muscles of Mastication

• Masseter
• the strongest jaw muscle
• Temporalis
• helps lift the mandible
• Pterygoid muscles
• position mandible for chewing

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Summary Muscles of Mastication
Table 114
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Muscles of the Tongue
Figure 117
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4 Muscles of the Tongue

• Palatoglossus
• originates at palate
• Styloglossus
• originates at styloid process
• Genioglossus
• originates at chin
• Hypoglossus
• originates at hyoid bone

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Summary Muscles of the Tongue
Table 115
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Muscles of the Pharynx
Figure 118
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3 Muscles of the Pharynx

• Pharyngeal constrictor muscles
• move food into esophagus
• Laryngeal elevator muscles
• elevate the larynx
• Palatal muscles
• lift the soft palate

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Summary Muscles of the Pharynx
Table 116
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Anterior Muscles of the Neck
Figure 119
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6 Anterior Muscles of the Neck

• Digastric
• from chin to hyoid
• and hyoid to mastoid
• Mylohyoid
• floor of the mouth
• Geniohyoid
• between hyoid and chin
• Stylohyoid
• between hyloid and styloid
• Sternocleidomastoid
• from clavicle and sternum to mastoid
• Omohyoid
• attaches scapula, clavicle, first rib, and hyoid

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Summary Anterior Muscles of the Neck
Table 117
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Muscles of the Vertebral Column
Figure 1110a
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Muscles of the Vertebral Column

• Spinal extensors or erector spinae muscles
  (superficial and deep)
• Spinal flexors (transversospinalis)

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Superficial Spinal Extensors

• Spinalis group
• Longissimus group
• Iliocostalis group
• Deep Spinal Extensors
• Semispinalis group
• Multifidus muscle
• Interspinalis muscles
• Intertransversarii muscles
• Rotatores muscles

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Spinal Flexors

• Neck
• longus capitis and longus colli
• rotate and flex the neck
• Lumbar
• quadratus lumborum muscles
• flex spine and depress ribs

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Summary Muscles of the Vertebral Column
Table 118 (1 of 2)
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Summary Muscles of the Vertebral Column
Table 118 (2 of 2)
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Oblique and Rectus Muscles

• Lie within the body wall

Figure 1111a, b
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Oblique and Rectus Muscles
Figure 1111a, c
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Oblique and Rectus Muscles

• Oblique muscles
• compress underlying structures
• rotate vertebral column
• Rectus muscles
• flex vertebral column
• oppose erector spinae

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Oblique Muscles

• Cervical region
• scalene muscles
• flex the neck
• Thoracic region
• intercostal muscles (external and internal
  intercostals)
• respiratory movements of ribs
• transversus thoracis
• cross inner surface of ribs

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Oblique Muscles

• Abdominopelvic region (same pattern as thoracic)
• external oblique muscles
• internal oblique muscles
• Transversus abdominis

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Rectus Group

• Rectus abdominis
• between xiphoid process and pubic symphysis
• divided longitudinally by linea alba
• divided transversely by tendinous inscriptions
• Diaphragmatic muscle or diaphragm
• divides thoracic and abdominal cavities
• performs respiration

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Summary Oblique and Rectus Muscles
Table 119 (1 of 2)
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Summary Oblique and Rectus Muscles
Table 119 (2 of 2)
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Muscles of the Pelvic Floor
Figure 1112a
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Muscles of the Pelvic Floor
Figure 1112b
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Functions of Pelvic Floor Muscles

• Support organs of pelvic cavity
• Flex sacrum and coccyx
• Control movement of materials through urethra and
  anus

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Perineum

• Muscular sheet forming the pelvic floor, divided
  into
• anterior urogenital triangle
• posterior anal triangle
• Pelvic Diaphragm
• Deep muscular layer extending to pubis
• supports anal triangle

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Urogenital Diaphragm

• Deep muscular layer between pubic bones
• supports the pelvic floor
• and muscles of the urethra
• Superficial muscles of the urogenital triangle
• support external genitalia

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Summary Muscles of the Pelvic Floor
Table 11-10 (1 of 2)
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Summary Muscles of the Pelvic Floor
Table 11-10 (2 of 2)
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What are the principal appendicular muscles of
the body and their origins, insertions, actions,
and innervations?
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The Appendicular Muscles
Figure 1113a
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The Appendicular Muscles
Figure 1113b
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The Appendicular Muscles

• Position and stabilize pectoral and pelvic
  girdles
• Move upper and lower limbs

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Divisions of Appendicular Muscles

• 1) Muscles of the shoulders and upper limbs
• Position the pectoral girdle
• Move the arm
• Move the forearm and hand
• Move the hand and fingers
• 2) Muscles of the pelvis and lower limbs

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Muscles that Position the Pectoral Girdle
3D Peel-Away of Muscles of the Pectoral Girdle
PLAY
Figure 1114a
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Muscles that Position the Pectoral Girdle
Figure 1114b
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6 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

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6 Muscles that Position the Pectoral Girdle

• Serratus anterior
• on the chest
• originates along ribs
• inserts on anterior scapular margin
• Subclavius
• originates on ribs
• inserts on clavicle
• Pectoralis minor
• attaches to scapula

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Summary 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 (1 of 3)

• Deltoid
• the major abductor
• Supraspinatus
• assists deltoid
• Subscapularis and teres major
• produce medial rotation at shoulder

3D Rotation Muscles of the Arm
PLAY
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9 Muscles that Move the Arm (2 of 3)

• Infraspinatus and teres minor
• produce lateral rotation at shoulder
• Coracobrachialis
• attaches to scapula
• produces flexion and adduction at shoulder

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9 Muscles that Move the Arm (3 of 3)

• 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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Summary Muscles that Move the Arm
Table 1112
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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)
• the major extensor (triceps brachii)

3D Rotation Muscles of the Forearm and Hand
PLAY
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Extensors and Flexors

• Extensors
• mainly on posterior and lateral surfaces of arm
• Flexors
• mainly on anterior and medial surfaces

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13 Muscles that Move the Forearm and Hand

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

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13 Muscles that Move the Forearm and Hand

• Anconeus
• opposes brachialis
• Palmaris longus
• superficial
• flexes wrist
• Flexor carpi ulnaris
• superficial
• flexes wrist
• adducts wrist

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13 Muscles that Move the Forearm and Hand

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

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13 Muscles that Move the Forearm and Hand (8 of
8)

• Pronator teres and supinator
• originate on humerus and ulna
• rotate radius
• Pronator quadratus
• originates on ulna
• assists pronator teres

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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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Muscles that Move the Hand and Fingers

• Also called extrinsic muscles of the hand
• Lie entirely within forearm
• Only tendons cross wrist (in synovial tendon
  sheaths)

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Tendon Sheaths

• Extensor retinaculum
• wide band of connective tissue
• posterior surface of wrist
• stabilizes tendons of extensor muscles
• Flexor retinaculum
• anterior surface of wrist
• stabilizes tendons of flexor muscles

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Summary Muscles that Move the Hand and Fingers
Table 1114
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The Intrinsic Muscles of the Hand
Figure 1118a
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The Intrinsic Muscles of the Hand
Figure 1118b
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Summary The Intrinsic Muscles of the Hand
Table 1115 (1of 2)
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Summary The Intrinsic Muscles of the Hand
Table 1115 (2of 2)
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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
• Muscles that Position the Lower Limbs
• Muscles that move the thigh
• Muscles that move the leg
• 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

3D Peel-Away of Muscles of the Thigh
PLAY
3D Peel-Away of Rectus Muscle
PLAY
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Gluteal Muscles (1 of 2)

• Cover lateral surfaces of ilia
• Gluteus maximus
• largest, most posterior gluteal muscle
• produces extension and lateral rotation at hip

128
Gluteal Muscles (2 of 2)

• Tensor fasciae latae
• works with gluteus maximus
• stabilizes iliotibial tract
• Gluteus medius and gluteus minimus
• originate anterior to gluteus maximus
• insert on trochanter

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Lateral Rotators

• Group of 6 muscles, including
• piriformis
• obturator

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Adductors

• Adductor magnus
• produces adduction, extension, and flexion
• Adductor brevis
• hip flexion and adduction
• Adductor longus
• hip flexion and adduction
• Pectineus
• hip flexion and adduction
• Gracilis
• hip flexion and adduction

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Iliopsoas

• 2 hip flexors insert on the same tendon
• psoas major
• iliacus

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Summary Muscles that Move the Thigh
Table 1116 (1 of 2)
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Summary Muscles that Move the Thigh
Table 1116 (2 of 2)
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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 of the Knee

• Biceps femoris- Hamstrings
• Semimembranosus-
• Semitendinosus-
• Sartorius
• originates superior to the acetabulum
• Popliteus
• rotates the tibia to unlock the knee

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Extensors of the Knee

• 4 muscles of the quadriceps femoris
• 3 vastus muscles
• rectus femoris muscle

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Summary Muscles that Move the Leg
Table 1117 (1 of 2)
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Summary Muscles that Move the Leg
Table 1117 (2 of 2)
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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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4 Muscles that Produce Extension at the Ankle

• Gastrocnemius
• Soleus
• Fibularis
• Tibialis posterior
• The Achilles Tendon-
• The calcaneal tendon (Achilles tendon)
• shared by the gastrocnemius and soleus

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Muscles that Produce Flexion at the Ankle

• Tibialis anterior
• opposes the gastrocnemius
• Muscles that Produce Flexion at the Toes
• Flexor digitorum longum
• Flexor hallucis longus
• oppose the extensors

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Muscles that Produce Extension at the Toes

• Extensor digitorum longum
• Extensor hallucis longus
• Extensor retinacula
• fibrous sheaths hold tendons of toes as they
  cross the ankle

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Summary Muscles that Move the Foot and Toes
Table 1118
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The Intrinsic Muscles of the Foot
Figure 1122a
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The Intrinsic Muscles of the Foot
Figure 1122b, c
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Summary The Intrinsic Muscles of the Foot
Table 1119
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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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Integration with Other Systems
Figure 1124
153
Integration with Other Systems

• Cardiovascular system
• delivers oxygen and fuel
• removes carbon dioxide and wastes
• Respiratory system
• responds to oxygen demand of muscles
• Integumentary system
• disperses heat from muscle activity
• Nervous and endocrine systems
• direct responses of all systems

154
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