Chapter 10
Muscular System
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
Function of Skeletal Muscles
1) Help maintain homeostasis
2) Produce body movements
Skeletal Muscles
There are more than 600 muscles in the
body.
40 to 50 percent of our body is skeletal
muscle.
Connective tissue components
Endomysium- covers
specialized skeletal
muscle fibers
Perimysium- binding
together fascicles
Epimysium- sheath
covering the muscle
as a whole
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
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
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
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)
Types of levers
1) First class leverfulcrum lies between
pull and the load
Not abundant in the
human body; serve as
levers of stability
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
Types of levers
Third-class leversPull is exerted
between the fulcrum
and the load
Permit rapid and
extensive movement
Most common type of
lever found in the
body
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
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)
Muscles for Mastification
Masseter- Closes jaw
Temporalis- Closes jaw
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
Muscles of the Thorax
External intercostals- Elevate ribs
Internal intercostals- Depress ribs
Diaphragm- Enlarges thorax, causing
inspiration
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
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
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
Upper arm cont.
Teres major- Assist in extension,
adduction, and medial rotation of arm
Infraspinatus- Rotates arm outward
Subscapularis- medial rotation
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
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
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/mangusadducts thigh)
Gracilis- adducts tigh and flexes and adducts leg
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
Muscles moving lower leg cont.
Hamstring group:
Biceps femoris- Flexes leg
Semitendinosus- Extends thigh
Semimembranosus- Extends thigh
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