Muscular System

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Chapter 10

• Muscular System

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Three types of muscles

• 1) smooth muscles- involuntary muscles example
  large and small intestines
• 2) Cardiac muscles- involuntary muscle example
  heart
• 3) Skeletal muscles- voluntary muscles example
  muscles attached to bones

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Function of Skeletal Muscles

• 1) Help maintain homeostasis
• 2) Produce body movements

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Skeletal Muscles

• There are more than 600 muscles in the body.
• 40 to 50 percent of our body is skeletal muscle.

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Connective tissue components

• Endomysium- covers specialized skeletal muscle
  fibers
• Perimysium- binding together fascicles
• Epimysium- sheath covering the muscle as a whole

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Three ways muscles are arranged

• 1) Size- small to large masses
• 2) Shape- broad, narrow, long, tapering, short,
  blunt, triangular, quadrilateral, irregular, flat
  sheets, or bulky masses
• 3) Arrangement- parallel to long axis, converge
  to a narrow attachment, oblique, pennate,
  bipennate, or curved

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Attachment of muscles

• 1) Origin- point of attachment that does not move
  when the muscle contracts
• 2) Insertion- point of attachment that moves when
  muscles contract

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Muscle actions

• 1) Prime movers (agonist)- muscle or group of
  muscles that directly performs a specific
  movement
• 2) Antagonist- muscle that, when contracting,
  directly oppose prime movers relax while prime
  mover (agonist) is contracting to produce
  movement provide precision and control during
  contraction of prime movers
• 3) synergists- muscles that contract at the same
  time as the prime movers they facilitate prime
  mover actions to produce a more efficient
  movement
• 4) Fixator muscles- joint stabilizers

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Lever system

• Composed of 4 components
• 1) Rigid bar (bone)
• 2) Fulcrum (F) around which the rod moves (joint)
• 3) Load (L) that is moved
• 4) Pull (P) that produces movement (muscle
  contraction)

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Types of levers

• 1) First class lever- fulcrum lies between pull
  and the load
• Not abundant in the human body serve as levers
  of stability

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Types of levers

• 2) Second Class lever- Load lies between the
  fulcrum and the joint at which the pull is
  exerted
• Presence of these levers in the human body is a
  controversial issue

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Types of levers

• Third-class levers- Pull is exerted between the
  fulcrum and the load
• Permit rapid and extensive movement
• Most common type of lever found in the body

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Naming Muscles

• 1) Location, function, shape
• 2) Direction of fibers- named according to fiber
  orientation
• 3) Number of heads of divisions
• 4) Points of attachment- origin and insertion
  points
• 5) Relative size- small, medium, or large
• Read page 286 on hints on how to deduce muscle
  action

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Facial Muscles

• Occipitofrontals- Raises eyebrows, wrinkles
  forehead
• Orbicularis oculi- closes eyes
• Zygomaticus major- Laughing
• Orbicularis oris- Draws lips together
• Buccinator- Permits smiling (no Coach Bryant does
  not have this muscle)

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Muscles for Mastification

• Masseter- Closes jaw
• Temporalis- Closes jaw

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Muscles that move head

• Sternocleidomastoid- Flexes head, one muscle
  alone, rotates head toward opposite side
• Semispinalis capitis- Extends head bends it
  laterally
• Splenius capitis- Extends head/ Bends and rotates
  head toward same side as contracting muscle
• Longissimus capitis- Extents head

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Muscles of the Thorax

• External intercostals- Elevate ribs
• Internal intercostals- Depress ribs
• Diaphragm- Enlarges thorax, causing inspiration

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Muscles of the Abdominal Wall

• External oblique- Compresses abdomen/ rotates
  trunk laterally
• Internal oblique- same as external oblique
• Transverse abdominis- same as external oblique
• Rectus abdominis- same as external oblique

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Muscles moving on Shoulder Girdle

• Trapezius- Raises or lowers shoulder and shrugs
  them
• Pectoralis minor- Pulls shoulder down and forward
• Serratus anterior- Pulls shoulder down and
  forward abducts and rotates it upward
• Levator scapulae- Elevates and retracts scapula
  and abducts neck.
• Rhomboid major and minor- Retracts, rotates,
  fixes scapula

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Muscles moving upper arm

• Pectoralis major- Flexes upper arm, Adducts upper
  arm anteriorly
• Latissimus dorsi- Extends upper arm, Adducts
  upper arm posteriorly
• Deltoid- Abducts upper arm
• Coracobrachialis- Adduction
• Supraspinatus- Assist in abducting arm
• Teres minor- rotates arm outward

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Upper arm cont.

• Teres major- Assist in extension, adduction, and
  medial rotation of arm
• Infraspinatus- Rotates arm outward
• Subscapularis- medial rotation

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Muscles moving the Forearm

• Biceps brachii- flexes supinated forearm
• Brachialis- flexes pronated forearm
• Brachioradialis- flexes semipronated or
  semisupinated forearm
• Triceps brachii- Extends lower arm
• Pronator teres- Pronates and flexer forearm
• Pronator quadratus- Pronates forearm
• Supinator- Supinates forearm

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Muscles that move the hand

• Flexor carpi radialis- Flexes hand/forearm
• Flexor carpi ulnaris- Flexes hand/ adducts hand
• Extensor carpi radialis brevis- Extends hand
• Extensor carpi ulnaris- Extends hand/ Adducts
  hand
• Flexor digitorum- flexes fingers
• Extensor digitorum- extends fingers

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Muscles that move thigh

• Iliopsoas- Flexes thigh
• Rectus femoris- Flexes thigh/ extends lower leg
• Gluteal muscles (maximus- extends thigh/ medius-
  abducts thigh/ minimus- abducts thigh)
• Tensor fasciae latae- abducts thigh
• Adductor group- (brevis/longus/mangus- adducts
  thigh)
• Gracilis- adducts tigh and flexes and adducts leg

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Muscles that move lower leg

• Quadriceps femoris group
• Rectus femoris- Flexes thigh/ extends leg
• Vastus lateralis- Extends leg
• Vastus medialis- Extends leg
• Vastus intermedius- Extends leg
• Sartorius- Adducts and flexes leg

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Muscles moving lower leg cont.

• Hamstring group
• Biceps femoris- Flexes leg
• Semitendinosus- Extends thigh
• Semimembranosus- Extends thigh

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Muscles move the foot

• Tibialis anterior- Flexes/ Inverts foot
• Gastrocnemius- Extends foot/ Flexes lower leg
• Soleus- Extends foot (planter flexion)
• Peroneus longus- extends foot
• Peroneus brevis- Flexes foot
• Peroneus tertius- Flexes foot
• Extensor digitorum longus- Dorsiflexion of foot/
  extension of toes

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