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Muscular System
Origin, Insertion, Action
Muscles of the Scalp
• Occipitofrontalis
– Frontal Belly
– Occipital Belly
Frontalis
• O: Galea aponeurotica
• I: Skin of eyebrows
• A: Raises eyebrows,
wrinkles forehead skin
Occipitalis
• O: Occipital Bone
• I: Galea aponeurotica
• A: Pulls scalp posterior
Muscles of Facial Expression
Orbicularis Occuli
• O: Frontal and
Maxillary bones
• I: Tissue of eyelid
• A: Blinking, squinting
Orbicularis Oris
• O: Maxilla and
Mandible
• I: Encircles mouth,
angles of mouth
• A: Closes lips, purses
and protrudes lips
(kissing and whistling)
Muscles of Mastication
Masseter
• O: Zygomatic arch and
maxilla
• I: Mandible
• A: Closes jaw by
elevating mandible
Temporalis
• O: Temporal fossa
• I: Coronoid process of
mandible
• A: Closes jaw (elevates
and retracts mandible)
Buccinator
• O: Maxilla and
mandible
• I: Orbicularis oris
• A: Compresses cheek
(whistling and sucking),
holds food between
teeth (during chewing)
Muscles of the Anterior Neck and
Throat (Swallowing)
• Digastric
• All of the muscles that attach to the hyoid
Digastric
• O: Mandible and
mastoid process
• I: Hyoid bone
• A: Elevate hyoid during
speech and swallowing,
• Open mouth and
depress mandible
Anterolateral Neck Muscles
Sternocleidomastoid
• O: Sternum and
Clavicle
• I: Mastoid process of
temporal bone
• A: B/L – head flexion;
unilateral – laterally flex
towards and rotates
away from itself
Scalenes
• O: Transverse
processes (anterior) of
cervical vertebrae
• I: 1st two ribs
• A: elevate first two ribs
(inspiration), flex and
rotate neck
Intrinsic Muscles of the Back
Splenius Capitus
• O: Ligamentum
nuchae, spinous
processes of C7 – T-6
• I: Occipital bone,
mastoid process of
temporal bone
• A: B/L – extend head;
unilateral – lateral flex
and rotate towards
Splenius Cervicis
• O: Ligamentum
nuchae, spinous
processes of C7 – T-6
• I: Transverse Processes
of C2 – C4
• A: B/L – extend neck;
unilateral – lateral flex
and rotate towards
Erector Spinae (Sacrospinalis)
• Iliocostalis (Most lateral)
• Longissimus (Intermediate)
• Spinalis (Most medial)
Iliocostalis
• O: iliac crest
(lumborum); inferior 6
ribs (thoracis); ribs 3 to
6 (cervicis)
• I: ribs (lumborum and
thoracic); TPs of C6-C4
(cervicis)
• A: B/L - Extend spine,
posture; unilateral –
lateral flex towards
Longissimus
• O: TPs of vertebrae
• I: Superior TPs and
superior ribs; capitis
portion inserts on
Mastoid process
• A: B/L – extend spine;
unilateral – laterally
flex; capitis portion
extends head and
rotates towards
Spinalis
• O: Spines of upper
lumbar and lower
thoracic vertebrae
• I: Spines of upper
thoracic and cervical
vertebrae
• A: Extends spine,
maintains erect posture
Quadratus Lumborum
• O: Iliac crest
• I: TPs of upper lumbar
vetebrae and 12th rib
• A: Unilaterally –
laterally flexes spine; b/l
– extends L-spine
Muscles of the Thorax (Breathing)
External Intercostals
• O: Inferior border of
rib above
• I: Superior border of rib
below
• A: Pull ribs toward one
another, elevate rib
cage; INSPIRATION
• Fibers run down and
anterior
Internal Intercostals
• O: Superior border of
rib below
• I: inferior border of rib
above
• A: Draw ribs together
and depress rib cage;
EXPIRATION
• Fibers run down and
posterior
Diaphragm
• O: Inferior surface of
rib cage and sternum,
costal cartilages, lumbar
vertebrae
• I: Central tendon
• A: Flattens on
contraction; Prime
mover of Inspiration
Muscles of the Anterior and Lateral
Abdominal Wall
Rectus Abdominus
• O: Pubic crest and
symphysis
• I: Xiphoid process and
costal cartilages ribs 5-7
• A: Flex and rotate
lumbar region, stabilize
pelvis during walking
External Oblique
• O: Outer surfaces of
lower eight ribs
• I: Linea alba
• A: B/L – aid in trunk
flexion; unilateral –
trunk rotation and
lateral flexion
Internal Oblique
• O: Lumbar fascia, iliac
crest
• I: linea alba, pubic
crest, costal margin last
3 – 4 ribs
• A: B/L – aid in trunk
flexion; unilateral –
trunk rotation and
lateral flexion
Transverse Abdominus
• O: Inguinal ligament,
lumbar fascia, cartilage
of last 6 ribs, iliac crest
• I: Linea alba, pubic
crest
• A: Compresses
abdominal contents
Muscles of the Anterior Thorax
Pectoralis Minor
• O: Anterior surface of
ribs 3-5
• I: Coracoid process of
scapula
• A: Ribs fixed – draws
scapula forward and
down; scapula fixed –
draws rib cage superior
Muscles of the Posterior Thorax
Trapezius
• O: Occipital bone,
ligamentum nuchae,
spines from C7 to T12
• I: Acromion and spine
of scapula, lateral 1/3 of
clavicle
• A: Superior – elevates
scapula; middle –
retract (adduct)
scapula; inferior –
depress scapula
Levator Scapulae
• O: Transverse
processes of C1 – C4
• I: Medial border of
scapula (superior to
spine)
• A: Elevates / adducts
scapula, laterally flexes
neck to same side
Rhomboids
• O: Spinous processes of
C7 – T5
• I: Medial border of
scapula
• A: Retract (adduct)
scapula, stabilize
scapula
Muscles Crossing the Shoulder Joint
Pectoralis Major
• O: Sternal end of
clavicle, sternum,
cartilage ribs 1-6
• I: Intertubercular sulcus
of humerus
• A: Flexes arm, medially
rotates arm, adducts
arm (climbing,
throwing, pushing)
Latissimus Dorsi
• O: Fascial connection
to spines of T7 – L5,
lower 3-4 ribs, iliac crest
• I: Intertubercular sulcus
of humerus
• A: Arm extension, arm
adductor, medially
rotates arm
(hammering,
swimming)
Deltoid
• O: Embraces insertion of
trapezius; lateral third of
clavicle, acromion, spine
of scapula
• I: Deltoid tuberosity of
humerus
• A: Abducts arm; anterior
fibers – flexion, medial
rot.; posterior fibers –
extension, lateral rot.
Rotator Cuff Muscles
•
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SITS
Supraspinatus
Infraspinatus
Teres Minor
Subscapularis
Supraspinatus
• O: Supraspinous fossa
of scapula
• I: Greater tubercle of
humerus
• A: Stabilizes shoulder
joint. Prevents
downward dislocation.
Initiates shoulder
abduction.
Infraspinatus
• O: Infraspinous fossa of
scapula
• I: Greater tubercle of
humerus posterior to
supraspinatus insertion
• A: Holds head of
humerus in glenoid
cavity, shoulder
stabilization
Teres Minor
• O: Lateral border of
scapula (dorsal surface)
• I: Greater tubercle of
humerus inferior to
infraspinatus insertion
• A: Stabilize shoulder,
adducts arm
Subscapularis
• O: Subscapular fossa of
scapula
• I: Lesser tubercle of
humerus
• A: Medial rotation of
humerus, stabilizes
shoulder joint
Teres Major
• O: Inferior angle of
scapula
• I: Intertubercular sulcus
of humerus
• A: Extends, medially
rotates, and adducts
humerus
Coracobrachialis
• O: Coracoid process of
scapula
• I: Medial humerus
• A: Flexion and
adduction of humerus
Muscles Crossing the Elbow Joint
Posterior
Triceps Brachii
• O: Scapula and
humerus
• I: Olecranon process of
ulna
• A: Forearm extensor
Anterior
Biceps Brachii
• O: Short head –
coracoid process; long
head – lip of glenoid
cavity
• I: Radial tuberosity
• A: Flexes elbow joint,
supinates forearm
Brachialis
• O: Front of distal
humerus
• I: Styloid process of
ulna
• A: Forearm flexor
Brachioradialis
• O: Distal end of
humerus
• I: Styloid process of
radius
• A: Forearm flexion
Muscles of the Forearm
Anterior Superficial
Pronator Teres
• O: Medial epicondyle
of humerus
• I: Lateral radius
• A: Pronates forearm
Flexor Carpi Radialis
• O: Medial epicondyle
of humerus
• I: 2nd and 3rd
metacarpals
• A: Flexor of wrist,
abducts hand
Palmaris Longus
• O: Medial epicondyle
of humerus
• I: Skin and fascia of
palm
• A: Wrist flexor
Flexor Carpi Ulnaris
• O: Medial epicondyle
of humerus, olecranon
process and posterior
ulna
• I: Pisiform, hamate, and
5th metacarpal
• A: Wrist flexion,
adducts hand
Flexor Digitorum Superficialis
• O: Medial epicondyle
of humerus, coronoid
process of ulna, shaft of
radius
• I: Middle phalanges 25.
• A: Flexes wrist and
middle phalanges
Anterior Deep
Flexor Pollicis Longus
• O: Anterior radius,
interosseus membrane
• I: Distal phalanx of the
thumb
• A: Flexes distal phalanx
of the thumb
Flexor Digitorum Profundus
• O: Anteromedial
surface of ulna and
interosseus membrane
• I: Distal phalanges 2-5
• A: Finger flexion
Posterior Superficial
Extensor Carpi Radialis
• O: Lateral epicondyle of
humerus
• I: 3rd metacarpal
• A: Extends wrist
Extensor Carpi Digitorum
• O: Lateral epicondyle of
humerus
• I: Distal phalanges 2-5
• A: Finger extension,
extends wrist
Extensor Carpi Ulnaris
• O: Lateral epicondyle of
humerus, posterior ulna
• I: 5th metacarpal
• A: Extends wrist,
adducts wrist
Posterior Deep
Supinator
• O: Lateral epicondyle of
humerus, proximal ulna
• I: Proximal radius
• A: Supinates forearm
Extensor Pollicis
• O: Dorsal radius and
ulna, interosseus
membrane
• I: Proximal and distal
phalanx of thumb
• A: Extends thumb
Thenar Muscles
Abductor Pollicis
• O: Posterior radius and
ulna, interosseus
membrane
• I: 1st metacarpal and
trapezium
• A: Abducts and extends
thumb, abducts wrist
Opponens Pollicis
• O: Flexor retinaculum
and trapezium
• I: Anterior 1st
metacarpal
• A: Opposition: moves
thumb to touch tip of
middle finger
Adductor Pollicis
• O: Metacarpals 2-4
• I: Medial side of
proximal phalanx of
thumb
• A: Adducts thumb
Muscles Crossing the Hip and Knee
Joints
Anterior and Medial Muscles
Iliopsoas
• O: Iliac crest, TPs,
bodies, and discs of T12
– L5
• I: Lesser trochanter of
femur
• A: Thigh flexor, trunk
flexor, lateral flexion of
trunk
Sartorius
• O: Anterior Superior
Iliac Spine (ASIS)
• I: Posterior, medial
aspect of proximal Tibia
• A: Flexes, abducts, and
laterally rotates thigh;
flexes knee
Medial Compartment of the Thigh
Gracilis
• O: Body of pubis
• I: Medial surface of
Tibia
• A: Adducts thigh; flexes
thigh; medially rotates
thigh
Anterior Compartment of the
Thigh
Quadriceps Femoris
• Four Heads
– Rectus Femoris
– Vastus Lateralis
– Vastus Medialis
– Vastus Intermedius
Rectus Femoris
• O: Anterior Inferior Iliac
Spine (AIIS)
• I: Patella and tibial
tuberosity
• A: Extends knee; flexes
thigh at hip
Vastus Lateralis
• O: Greater trochanter
• I: Patella and tibial
tuberosity
• A: Extends and
stabilizes knee
Vastus Medialis
• O: Linea aspera,
intertrochanteric line
• I: Patella and tibial
tuberosity
• A:Extends knee; inferior
fibers stabilize patella
Vastus Intermedius
• O: Anterior and lateral
surface of proximal
femur
• I: Patella and tibial
tuberosity
• A: Extends knee
Tensor Fascia Latae
• O: Iliac crest, ASIS
• I: Iliotibial tract
• A: Flexes and abducts
thigh; pulls iliotibial
tract taut
Posterior Muscles
Gluteus Maximus
• O: Dorsal ilium, sacrum,
coccyx
• I: Gluteal tuberosity of
femur, ITB
• A: Extends thigh
Gluteus Medius & Minimus
• O: Surface of ilium
• I: Greater trochanter of
femur
• A: Abducts and
medially rotates thigh
Lateral Rotators
Piriformis
• O: Anterolateral
surface of sacrum
• I: Greater trochanter of
femur (superior border)
• A: Laterally rotates
thigh
Posterior Compartment of the Thigh
Hamstrings
• Biceps femoris (two heads)
• Semitendinosus
• Semimembranosus
Biceps Femoris
• O: Ischial tuberosity
• I: Head of fibula and
lateral condyle of tibia
• A: Extends thigh; flexes
knee; laterally rotates
leg
Semitendinosus
• O: Ischial tuberosity
• I: Medial aspect of
Tibia
• A: Extends thigh; flexes
knee; medially rotates
leg
Semimembranosus
• O: Ischial tuberosity
• I: Medial condyle of
tibia; lateral condyle of
femur
• A: Extends thigh; flexes
knee; medially rotates
leg
Muscles of the Leg
Anterior Compartment
Tibialis Anterior
• O: Upper 2/3 of tibia,
interosseus membrane
• I: Medial cuneiform
and 1st metatarsal bone
• A: Dorsiflexion of foot
Extensor Digitorum
• O: Proximal ¾ of fibula;
interosseous membrane
• I: Middle and distal
phalanges of toes 2-5
• A: Toe extension;
dorsiflexes foot
Extensor Hallucis
• O: Fibula; interosseous
membrane
• I: Distal phalanx of
great toe
• A: Extends great toe;
dorsiflexes foot
Lateral Compartment
Peroneus (Fibularis)
• O: Lateral fibula
• I: Long tendon curves
under foot to the 1st
metatarsal and medial
cuneiform (longus); fifth
metatarsal (brevis)
• A: Plantar flexes foot;
everts foot.
Posterior Compartment
Triceps Surae
• Gastrocnemius (Two heads)
• Soleus
Gastrocnemius
• O: Two heads from
medial and lateral
condyles of the femur
• I: Calcaneus
• A: Plantar flexes foot;
can flex knee when the
foot is dorsiflexed
Soleus
• O: Superior tibia and
fibula; interoesseous
membrane
• I: Calcaneus
• A: Plantar flexes foot
Flexor Digitorum Longus
• O: Posterior Tibia
• I: Distal phalanges 2-5
• A: Plantar flexion of
foot and flexion of the
toes.