THE MUSCULAR SYSTEM

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THE MUSCULAR SYSTEM
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INTERACTIONS OF SKELETAL MUSCLES IN THE BODY

• Muscles only pull they are not capable of
  pushing
• Generally as a muscle shortens, its insertion
  (attachment on the movable bone) moves toward its
  origin (its fixed or immovable point of
  attachment)
• Muscles can be classified into four functional
  groups
• 1.Prime Movers
• The muscle that provides the major force for the
  specific movement is called the prime mover or
  the agonist, of that movement
• The biceps brachii muscle, which fleshes out the
  anterior arm (and inserts on the radius), is a
  prime mover of elbow flexion
• 2.Antagonists
• Muscles that oppose or reverse a particular
  movement
• When a prime mover is active, the antagonist
  muscles are often stretched and may be relaxed
• Can also help to regulate the action of a prime
  mover by contracting to provide some resistance,
  thus helping to prevent overshoot or to slow or
  stop the movement
• Prime mover and its antagonist are located on
  opposite sides of the joint across which they act
• Antagonists can also be prime movers in their own
  right
• Example flexion of the forearm by the biceps
  brachii muscle of the arm is antagonized by the
  triceps brachii, the prime mover for extending
  the forearm

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INTERACTIONS OF SKELETAL MUSCLES IN THE BODY

• 3.Synergists
• Help the prime movers by
• Adding a little extra force to the same movement
• Or reducing undesirable or unnecessary movements
  that might occur as the prime mover contracts
• When a muscle crosses two or more joints, its
  contraction causes movement at all of the spanned
  joints unless other muscles act as joint
  stabilizers
• Example the finger flexor muscles cross both the
  wrist and the phalangeal joints, but you can make
  a fist without bending your wrist because
  synergistic muscles stabilize the wrist
• As some flexors act, undesirable rotation
  movements occur
• Synergists can prevent this, allowing all of the
  prime movers force to be exerted in the desired
  direction

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INTERACTIONS OF SKELETAL MUSCLES IN THE BODY

• 4.Fixators when synergists immobilize a bone, or
  a muscles origin, they are more specifically
  called fixators
• Examples
• Scapula is held to the axial skeleton only by
  muscles and is quite freely movable
• The fixator muscles that run from the axial
  skeleton to the scapula can immobilize the
  scapula so that only the desired movements occur
  at the mobile shoulder joint
• Muscles that help to maintain upright posture

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INTERACTIONS OF SKELETAL MUSCLES IN THE BODY

• Although prime movers seem to get all the credit
  for causing certain movements, antagonistic and
  synergistic muscles are also important in
  producing smooth, coordinated, and precise
  movements
• A muscle may act as a prime mover in one
  movement, an antagonist for another movement, a
  synergist for a third movement, and so on

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NAMING SKELETAL MUSCLES

• 1. Location of the muscle Some muscle names
  indicate the bone or body region with which the
  muscle is associated
• Example
• Temporalis muscle overlies the temporal bone
• Intercostal muscles run between the ribs
• 2. Shape of the muscle Some muscles are named
  for their shape
• Example
• Deltoid muscle is roughly triangular
• Together the right and left trapezius muscles
  form a trapezoid
• 3. Relative size of the muscle Terms such as
  maximus (largest), minimus (smallest), longus
  (long), and brevis (short) are often used in
  muscle names to indicate relative size of the
  muscle
• Example
• Gluteus maximus
• Gluteus minimus

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NAMING SKELETAL MUSCLES

• 4. Direction of muscle fibers The names of some
  muscles indicate the direction in which their
  fibers (and fascicles) run in reference to some
  imaginary line, usually the midline of the body
  or the longitudinal axis of a limb bone
• Examples
• Rectus (straight) fibers run parallel to that
  imaginary line (axis)
• Rectus femoris straight muscle of the thigh, or
  femur)
• Transversus (right angle) muscle fibers run at
  right angles
• Transversus abdominis transverse muscle of the
  abdomen
• Oblique (oblique angle) muscle fibers run at
  oblique angles
• External oblique oblique muscle of the abdomen

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NAMING SKELETAL MUSCLES

• 5. Number of origins The number of origins a
  muscle has may be indicated by the word biceps,
  triceps, or quadriceps
• Example
• Biceps brachii muscle of the arm has two origins
  (heads)

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NAMING SKELETAL MUSCLES

• 6. Location of the attachments Some muscles are
  named according to the location of their origin
  and insertion
• Origin is always named first
• Example
• Sternocleidomastoid muscle of the neck
• Has a dual origin on the sternum (sterno) and
  clavicle (cleido), and it inserts on the mastoid
  process of the temporal bone

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NAMING SKELETAL MUSCLES

• 7. Action A muscle may be named for its action
  by using such words as flexor (flex), extensor
  (extend), adductor (brought toward), or supinate
  (bend backward) in its name
• Example
• Adductor longus located in the medial thigh
• Brings about thigh adduction (toward the main
  axis of the body or a limb)
• Supinator muscle
• Supinates the forearm
• Turn the forearm or hand so that the palm faces
  upward
• Supinates the leg and foot
• To rotate the foot and leg outward

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NAMING SKELETAL MUSCLES

• Several criteria are combined in the naming of
  some muscles
• Example extensor carpi radialis longus
• Action of the muscle the muscles action
  (extensor)
• Location of attachment joint it acts on (carpi
  wrist)
• Location of muscle lies close to the radius of
  the forearm (radialis)
• Relative size of muscle relative to other wrist
  extensor muscles (longus)
• Unfortunately, not all muscle names are this
  descriptive

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MUSCLE MECHANICSIMPORTANCE OF FASCICLE
ARRANGEMENT AND LEVERAGE

• In skeletal muscles the common arrangement of the
  fascicles varies, resulting in muscles with
  different shapes and functional capabilities

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Arrangement of Fascicles

• Fascicle bundle of nerve or muscle fibers
  (cells) bound together by connective tissue
• All skeletal muscles consist of fascicles, but
  fascicle arrangement vary, resulting in muscles
  with different shapes and functional capabilities

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SKELETAL MUSCLE
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Arrangement of Fascicles

• (a) Circular pattern
• Fascicles arranged in concentric rings
• Muscles with this arrangement surround external
  openings, which they close by contracting
• General term for these muscles is sphincters
  (squeezers)
• Examples
• Orbicularis muscles surrounding the eyes
  (Orbicularis oculi) and the mouth (Orbicularis
  oris)

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Arrangement of Fascicles

• (b) Convergent pattern
• Muscle has a broad origin, and its fascicles
  converge toward a single tendon of insertion
• Such a muscle is triangular or fan shaped like
  the pectoralis major muscle of the anterior
  thorax

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Arrangement of Fascicles

• (c)(f) Parallel pattern
• The long axes of the fascicles run parallel to
  the long axis of the muscle
• Such muscles are either
• straplike (c parallel)
• spindle (f fusiform)
• shaped with an expanded belly (midsection)
• Examples
• Sartorius of thigh (c)
• Biceps brachii muscle of the arm (f)

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Arrangement of Fascicles

• (d)(e)(g) Pennate pattern
• In a pennate (feather) pattern of arrangement the
  fascicles are short and attach obliquely to a
  central tendon that runs the length of the muscle
• Types
• Unipennate d
• Fascicles insert into only one side of the tendon
• Example extensor digitorum muscle of the leg
• Bipennate g
• Fascicles insert into the tendon from opposite
  sides (muscle grains resemble a feather)
• Example rectus femoris muscle of the thigh
• Multipennate e
• Arrangement looks like many feathers situated
  side by side, with all their quills inserted into
  one large tendon
• Example deltoid muscle, which forms the
  roundness of the shoulder

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FASCICLE ARRANGEMENT TO MUSCLE STRUCTURE
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MUSCLE MECHANICSIMPORTANCE OF FASCICLE
ARRANGEMENT AND LEVERAGE

• The operation of most skeletal muscles involves
  the use of leverage and lever systems,
  partnerships between the muscular and skeletal
  systems
• A lever is a rigid bar that moves on a fixed
  point, or a fulcrum, when a force is applied to
  it
• The applied force, or effort is used to move a
  resistance or load
• In your body, your joints act as the fulcrums,
  the bones as the levers, and the muscle
  contraction as the effort (force)
• Load (resistance) is the bone itself, along with
  overlying tissues and anything else you are
  trying to move with that lever

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Lever Systems

• A lever allows a given effort (force) to lift a
  heavier load (resistance), or to move a load
  (resistance) farther or faster, than it otherwise
  could
• (a)First-Class the load is close to the fulcrum
  and the effort is applied far from the fulcrum
• A small effort exerted over a relatively large
  distance can be used to move a large load over a
  small distance
• Such a lever is said to operate at a mechanical
  advantage and is commonly called a power lever

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Lever Systems

• (b) Third-Class
• Load is far from the fulcrum and the effort is
  applied near the fulcrum, the force exerted by
  the muscle must be greater than the load moved or
  supported
• This lever system operates at a mechanical
  disadvantage and is a speed lever
• These levers are useful because they provide
  rapid contractions with a wide range of motion

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MUSCLE LEVERAGE
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Lever Systems

• All levers follow the same basic principle
• Effort farther than load from fulcrum
  mechanical advantage
• Effort nearer than load to fulcrum mechanical
  disadvantage
• Lever systems that operate at a mechanical
  disadvantage (speed levers), force is lost but
  speed and range of movement are gained, and this
  can be a distinct benefit
• Lever systems that operate at a mechanical
  advantage (power levers) are slower, more stable,
  and used where strength is a priority

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Lever Systems

• There are three types of levers
• First-class
• Second-class
• Third-class

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Lever SystemsFirst-Class Levers

• (a) Effort is applied at one end of the lever
  and the load is at the other, with the fulcrum
  somewhere between
• Examples
• Seesaws
• Scissors
• Lift your head off your chest
• Some operate at a mechanical advantage
• Others operate at a mechanical disadvantage
• Action of the triceps muscle in extending the
  forearm against resistance (pushing)

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Lever SystemsSecond-Class Levers

• (b) Effort is applied at one end of the lever
  and the fulcrum is located at the other, with the
  load between them
• All second-class levers in the body work at a
  mechanical advantage because the muscle insertion
  (effort) is always farther from the fulcrum than
  is the load to be moved
• Levers of strength, but speed and range are
  sacrificed for that strength
• Examples
• Wheelbarrow
• Uncommon in the human body
• Best example is the act of standing on your toes

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Lever SystemsThird-Class Levers

• (c) Effort is applied between the load and the
  fulcrum
• Operate with great speed and always at a
  mechanical disadvantage
• Most skeletal muscles of the body
• Tend to be thicker and more powerful
• Permits a muscle to be inserted very close to the
  joint across which movement occurs
• Allows rapid, extensive movements with relatively
  little shortening of the muscle
• Examples
• Tweezers (forceps)
• biceps

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MUSCLE LEVERAGE
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Skeletal Muscles

• Over 600
• Book only list approximately 125 pairs of them

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ANTERIOR SUPERFICIAL MUSCLES
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DIAGRAMMATIC VIEW OF ANTERIOR MUSCLES
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POSTERIOR VIEWOF SUPERFICIAL MUSCLES
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DIAGRAMMATIC VIEW OF POSTERIOR MUSCLES
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Facial Muscles

• Muscles of the Head Facial Expression
• Muscles of the scalp include the epicranius
  consisting of the frontalis and the occipitalis
• Muscles of the face include corrugator
  supercilii, orbicularis oculi, zygomaticus,
  risorius, levator labii superioris, depressor
  labii inferioris, depressor anguli oris,
  orbicularis oris, mentalis, buccinator, and
  platysma

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MAJOR SKELETAL MUSCLES OF THE FACE

• Frontaliscranial (facial nerve) VII
• Raises the eyebrows (as in surprise)
• Wrinkles forehead skin horixzontally
• Cranial nerve VII
• Orbicularis oculicranial (facial nerve) VII
• Protects eyes from intense light and injury
• Produces blinking, squinting
• Draws the eyebrows inferiorly
• Orbicularis oriscranial (facial nerve) VII
• Closes lips
• Purses (pucker) and protrudes (stick out) lips
• Kissing and whistling muscle

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HEAD MUSCLES
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Muscles of the Head

• Mastication and Tongue Movement
• Muscles of mastication include the masseter,
  temporalis, medial pterygoid, lateral pterygoid,
  and the buccinator
• Muscles promoting tongue movement are the
  genioglossus, hypoglossus, and the styloglossus

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Mastication Muscles

• MasseterTemporaliscranial (trigeminal) nerve V
• Prime mover of jaw closure
• Elevates mandible
• Temporaliscranial (trigeminal) nerve V
• Closes jaw
• Elevates and retracts mandible
• Buccinatorcranial (facial) nerve VII
• Trampoline-like action
• Keeps food between grinding surfaces of teeth
  during chewing

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Mastication Muscles
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HEAD MUSCLES
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Mastication Muscles
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Tongue Muscles

• Genioglossuscranial (hypoglossal) nerve XII
• Primarily protrudes tongue, but in concert with
  other extrinsic muscles to retract tongue

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TONGUE MUSCLES
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MAJOR SKELETAL MUSCLES OF THE BODY

• Muscles of the Anterior Neck and Throat
  Swallowing
• Suprahyoid muscles include digastric, stylohyoid,
  mylohyoid, and geniohyoid
• Infrahyoid muscles include sternohyoid,
  sternothyroid, omohyoid, thyrohyoid, and the
  pharyngeal constrictor muscles (superior, middle,
  and inferior)

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Neck and Throat Muscles

• Mylohyoidcranial (trigeminal) nerve V
• Elevates hyoid bone and floor of mouth
• Enables the tongue to exert backward and upward
  pressure that forces food bolus into pharynx

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Neck and Throat Muscles

• Pharyngeal constrictor muscles (superior, middle,
  and inferior)cranial (vagus) nerve X
• Working as a group and in sequence, all constrict
  pharynx during swallowing
• Propels food bolus to esophagus
• peristalsis

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NECK MUSCLES
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NECK MUSCLES
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MAJOR SKELETAL MUSCLES OF THE BODY

• Muscles of the Neck and Vertebral Column Head
  and Trunk Movement
• Anterolateral neck muscles include the
  sternocleidomastoid, and scalenes (anterior,
  middle, and posterior)
• Intrinsic muscles of the back include splenius
  capitis, erector spinae or sacrospinalis,
  iliocostals, longissimus, spinalis, semispinalis,
  and the quadratus lumborum

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Neck Muscles

• Sternocleidomastoid cranial (accessory) nerve XI
  and branches of cervical nerves 2-4
• Prime mover of head flexion
• Neck flexion
• Head movement side-to-side

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NECK AND VERTEBRAL COLUMN MUSCLES
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NECK AND VERTEBRAL COLUMN MUSCLES
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NECK AND VERTEBRAL COLUMN MUSCLES
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Neck and Vertebral Column Muscles

• Longissimus thoracis, cervicis, and capitis
  spinal nerves
• Capitis extends head and turns face side to side
• Thoracis and cervicis extend vertabral column
  side to side

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NECK AND VERTEBRAL COLUMN MUSCLES
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Thorax and Abdominal Muscles

• Muscles of the Thorax Breathing
• Muscles of the thorax include the external
  intercostals, internal intercostals, and the
  diaphragm
• Muscles of the Abdominal Wall Trunk Movement and
  Compression of Abdominal Viscera
• Muscles of the anterolateral abdominal wall
  include the rectus abdominis, external oblique,
  and the transversus abdominis

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Thorax Muscles

• External intercostals intercostal nerves
• Elevate rib cage
• Aids in inspiration
• Internal intercostals intercostal nerves
• Depress rib cage
• Aids in expiration
• Diaphragmcervical (phrenic) nerve (C3-C5)
• Breathing

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RESPIRATORY MUSCLES
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RESPIRATORY MUSCLES
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Abdominal Muscles

• Rectus abdominis Intercostal (thoracic) nerves
• Flex and rotate lumbar region
• External oblique Intercostal (thoracic) nerves
• Compression of abdominal wall
• Transversus abdominis Intercostal (thoracic)
  nerves
• Compression of abdominal wall

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ABDOMINAL MUSCLES
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ABDOMINAL MUSCLES
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MAJOR SKELETAL MUSCLES OF THE BODY

• Muscles of the Pelvic Floor and Perineum Support
  of Abdominopelvic Organs
• Muscles of the pelvic diaphragm include the
  levator ani and the coccygeus
• Muscles of the urogenital diaphragm include the
  deep transverse perineus and the sphincter
  urethrae
• Muscles of the superficial space include the
  ischiocavernosus, bulbospongiosus, and the
  superficial transverse perineus

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PELVIC FLOOR AND PERINEUM MUSCLES
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Pelvic Floor Muscles

• Ischiocavernosus pudendal (sacral) nerve
• Retards venous drainage and maintains erection of
  penis or clitoris
• Bulbospongiosus pudendal (sacral) nerve
• Empties male urethra
• Assist in erection of penis in males and of
  clitoris in females

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PELVIC FLOOR AND PERINEUM MUSCLES
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MAJOR SKELETAL MUSCLES OF THE BODY

• Superficial Muscles of the Anterior and Posterior
  Thorax Movements of the Scapula
• Muscles of the anterior thorax include the
  pectoralis minor, serratus anterior, and the
  subclavius
• Muscles of the posterior thorax include the
  trapezius, levator scapulae, and the rhomboids
  (major and minor)

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MAJOR SKELETAL MUSCLES OF THE BODY

• Muscles Crossing the Shoulder Joint Movement of
  the Arm
• Muscles moving the arm include the pectoralis
  major, latissimus dorsi, deltoid, subscapularis,
  supraspinatous, infraspinatous, teres minor,
  teres major, and the coracobrachialis

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Thorax Muscles

• Deltoid cervical nerves
• Prime mover of arm abduction
• Antagonists of pectoralis major and latissimus
  dorsi
• Pectoralis major cervical and thoracic nerves
• Prime mover of arm flexion
• Adduction
• Trapezius cervical nerves
• Stabilizes, raises, retracts, and rotates scapula
• Latissimus dorsi cervical nerves
• Prime mover of arm extension
• Powerful arm adductor
• Striking a blow
• Swimming
• Rowing

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THORAX MUSCLES
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SHOULDER MUSCLES
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MAJOR SKELETAL MUSCLES OF THE BODY

• Muscles crossing the Elbow Joint Flexion and
  Extension of the Forearm
• Posterior muscles include the triceps brachii,
  and the anconeus
• Anterior muscles include the biceps brachii,
  brachialis, and the brachioradialis

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SHOULDER MUSCLES

• Triceps brachii cervical nerves
• Powerful forearm extensor
• Biceps brachii cervical nerves
• Flexes elbow joint and supinates forearm
• Brachialis musculocutaneous nerve
• Major forearm flexor
• Lifts ulna as biceps lifts the radius
• Brachioradialis radial nerve
• Synergist in forearm flexion

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SHOULDER MUSCLES
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SHOULDER MUSCLES
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Forearm Muscles

• Flexor carpi radialis median nerve
• Powerful flexor of wrist
• Abducts hand
• Flexor carpi ulnaris ulnar nerve
• Powerful flexor of wrist
• Adducts hand

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ANTERIOR ARM MUSCLES
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Forearm Muscles

• Extensor carpi radialis brevis radial nerve
• Extends and abducts wrist
• Extensor digitorum branch of radial nerve
• Prime mover of finger extension
• Extends wrist

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POSTERIOR ARM MUSCLES
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ARM MUSCLES
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ARM MUSCLE ACTIONS
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ARM MUSCLE ACTIONS
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MAJOR SKELETAL MUSCLES OF THE BODY

• Muscles of the Forearm Movements of the Wrist,
  Hand, and Fingers
• Anterior superficial muscles include the pronator
  teres, flexor carpi radialis, palmaris longus,
  flexor carpi ulnaris, and the flexor digitorum
  superficialis
• Anterior deep muscles include the flexor pollicis
  longus, flexor digitorum profundus, and the
  pronator quadratus
• Posterior superficial muscles include the
  brachioradialis, extensor carpi radialis longus,
  extensor carpi radialis brevis, extensor
  digitorum, and the extensor carpi ulnaris
• Posterior deep muscles include the supinator,
  abductor pollicis longus, extensor pollicis
  longus, and the extensor pollicis brevis

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MAJOR SKELETAL MUSCLES OF THE BODY

• Intrinsic muscles of the Hand Fine Movements of
  the Fingers
• Thenar muscles in ball of thumb include the
  abductor pollicis brevis, flexor pollicis brevis,
  opponnens pollicis, and the adductor pollicis
• Hypothenar muscles in ball of little finger
  include the abductor digiti minimi, flexor digiti
  minimi brevis, and the opponens digiti minimi
• Midpalmar muscles include the lumbricals, palmar
  interossei, and the dorsal interossei

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Hand Muscles

• Abductor pollicis brevis median nerve
  (cervical.thoracic)
• Abducts thumb
• Flexor digiti minimi brevis ulnar nerve
• Flexes little finger

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HAND MUSCLES
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HAND MUSCLES
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MAJOR SKELETAL MUSCLES OF THE BODY

• Muscles Crossing the Hip and Knee Joints
  Movements of the Thigh and Leg
• Anteromedial muscles include the iliopsoas, which
  is composed of the iliacus, the psoas major, and
  the sartorius
• Muscles of the medial compartment of the thigh
  include the adductor group, which is made up of
  the adductor magnus, adductor longus and the
  adductor brevis, the pectineus, and the gracilis
• Muscles of the anterior compartment of the thigh
  include the quadriceps femoris group, which is
  made up of the rectus femoris, vastus lateralis,
  vastus medialis and vastus intermedius, and the
  tensor fasciae latae
• Posterior Muscles gluteal muscles (origin on
  pelvis) include the gluteus maximus, gluteus
  medius, and the gluteus minimus
• Lateral rotators include the piriformis,
  obturator externus, obturator internus, gemellus,
  and the quadratus femoris
• Muscles of the posterior compartment of the thigh
  include the hamstring group, which consist of the
  biceps femoris, semitendinosus, and the
  semimembranosus

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Thigh Muscles

• Adductor longus obturator nerve
• Adducts, flexes, and medially rotates thigh
• Gracilis obturator nerve
• Adducts thigh, flexes, and medially rotates
  thigh, especially during walking
• Quadriceps femoris
• Rectus femoris femoral nerve
• Extends knee and flexes thigh at hip

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ANTERIOR THIGH MUSCLES
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ANTERIOR THIGH MUSCLES
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Hip Muscles

• Gluteus maximus inferior gluteal nerve
• Major extensor of thigh
• Complex, powerful, and most effective when thigh
  is flexed and force is necessary, as in rising
  from a forward flexed position and in thrusting
  the thigh posteriorly in climbing stairs and
  running
• Inactive during standing

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POSTERIOR THIGH MUSCLES

• Hamstrings sciatic nerve
• Biceps femoris
• Semitendinosus
• Semimembranosus
• Extends thigh and flexes knee

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POSTERIOR THIGH MUSCLES
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POSTERIOR THIGH MUSCLES
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MAJOR SKELETAL MUSCLES OF THE BODY

• Muscles of the Leg Movements of the Ankle and
  Toes
• Muscles of the anterior compartment include the
  tibialis anterior, extensor digitorum longus,
  fibularis (peroneus) tertius, and the extensor
  hallucis longus
• Muscles of the lateral compartment include the
  fibularis (peroneus) longus and the fibularis
  (peroneus) brevis
• Superficial muscles of the posterior compartment
  include the triceps surae, which is composed of
  the gastrocnemius and the soleus, and the
  plantaris
• Deep muscles of the posterior compartment include
  the popliteus, flexor digitorum longus, flexor
  hallucis longus, and the tibialis posterior

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ANTERIOR LEG MUSCLES

• Tibialis anterior fibular nerve (lumbar)
• Prime mover of dorsiflexion
• Inverts foot
• Assists in supporting medial longitudinal arch of
  foot
• Fibularis longus fibular nerve (lumbar)
• Plantar flexes and everts foot
• May help keep foot flat on ground

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ANTERIOR LEG MUSCLES
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ANTERIOR LEG MUSCLES
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LATERAL LEG MUSCLES
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LATERAL LEG MUSCLES
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POSTERIOR LEG MUSCLES

• Gastrocnemius tibial nerve (sacral)
• Plantar flexes foot when knee is extended
• Since it also crosses knee joint, it can flex
  knee when foot is dorsiflexed
• Soleus tibial nerve (sacral)
• Plantar flexes foot
• Important locomotor and postural muscle during
  walking, running, and dancing

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POSTERIOR LEG MUSCLES
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POSTERIOR LEG MUSCLES
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POSTERIOR LEG MUSCLES
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POSTERIOR LEG MUSCLES
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LEG MUSCLE ACTIONS
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LEG MUSCLE ACTIONS
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MAJOR SKELETAL MUSCLES OF THE BODY

• Intrinsic Muscles of the Foot Toe Movement and
  Arch Support
• The muscle found on the dorsum of the foot is the
  extensor digitorum brevis
• Muscles on the sole of the foot found in the
  first layer are the flexor digitorum brevis,
  abductor hallucis, and the abductor digiti minimi
• Muscles on the sole of the foot found in the
  second layer are the flexor accessorius
  (quadratus plantae) and the lumbricals
• Muscles of the sole of the foot found in the
  third layer include the flexor hallicis brevis,
  adductor hallucis, and the flexor digiti minimi
  brevis
• Muscles of the sole of the foot found in the
  fourth layer include the plantar and the dorsal
  interossei

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Foot MusclesDorsum

• Extensor digitorum brevis fibular nerve
  (sacral)
• Helps extend toes

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Foot MusclesSole

• Flexor digitorum brevis medial plantar nerve
  (sacral)
• Helps flex toes

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FOOT MUSCLES
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FOOT MUSCLES
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FOOT MUSCLES