8.8
Major Skeletal Muscles
What muscle names tell us
Relative size
 Shape
 Location
 Action
 Number of attachments
 Direction of fibers

Examples
Zygomaticus – originates at the zygomatic
bone
 Gluteus maximus – originates in the
gluteal region and is a large muscle
 Tibialis anterior – originates on the
anterior surface of the tibia

Muscles of Facial Expression
Epicranus
Origin – occipital bone
 Insertion – skin and muscles around eye
 Action – raises eyebrow

Orbicularis oculi
Origin – maxillary and frontal bones
 Insertion – skin around eye
 Action – closes eye

Orbicularis oris
Origin – muscles near the mouth
 Insertion – skin of lips
 Action – closes and protrudes lips

Buccinator
Origin – outer surfaces of maxilla and
mandible
 Insertion – orbicularis oris
 Action – compresses cheeks inward

Zygomaticus
Origin – zygomatic bone
 Insertion – orbicularis oris
 Action – raises corner of mouth

Platysma
Origin – fascia in upper chest
 Insertion – lower border of mandible
 Action – draws angle of mouth downward

Muscles of Mastication
Masseter
Origin – lower border of zygomatic arch
 Insertion – lateral surface of mandible
 Action – closes jaw

Temporalis
Origin – temporal bone
 Insertion – coronoid process and lateral
surface of mandible
 Action – closes jaw

Muscles that move the head
Sternocleidomastoid
Origin – anterior surface of sternum and
upper surface of clavicle
 Insertion – mastoid process of temporal
bone
 Action – pulls head to one side, pulls head
toward chest, or raises sternum

Splenius capitis
Origin – spinous processes of lower cervical
and upper thoracic vertebrae
 Insertion – mastoid process of temporal
bone
 Action – rotates head, bends head to one
side, or brings head into an upright position.

Semispinalis capitis
Origin – processes of lower cervical and
upper thoracic vertebrae
 Insertion – occipital bone
 Action – extends head, bends head to one
side, or rotates head.

Muscles that move the pectoral
girdle
Closely associated with those that move the
arm.
 Many of these move the scapula up and
down, back and forth.

Muscles that move the pectoral
girdle
Trapezius
Origin – occipital bone and spines of
cervical and thoracic vertebrae
 Insertion – clavicle; spine and acromion
process of scapula
 Action – rotate scapula and raises arm,
raises scapula, pulls scapula medially or
pulls scapula and shoulder downward.

Rhomboideus major
Origin – spines of upper thoracic vertebrae
 Insertion – medial border of scapula
 Action – raises and adducts scapula

Levator scapula
Origin – transverse process of cervical
vertebrae
 Insertion – medial margin of scapula
 Action – elevates scapula

Serratus anterior
Origin – outer surface of upper ribs
 Insertion – ventral surface of scapula
 Action – pulls scapula anteriorly and
downward

Pectoralis minor
Origin – sternal ends of upper ribs
 Insertion – coracoid process of scapula
 Action – pulls scapula anteriorly and
downward or raises ribs

Muscles that move the arm
Arm is freely movable.
 Muscles are grouped by their primary
action.
 Flexion – flexors
 Extension – extensors
 Abduction – abductors
 Rotation - rotators

Flexors
Coracobrachialis
 Pectoralis major

Coracobrachialis
Extensors
Teres major
 Latissimus dorsi

Abductors
Supraspinatus
 Deltoid

Rotators
Subscapularis
 Infraspinatus
 Teres minor

Muscles that move the forearm
Most forearm movement is accomplished
by muscles that connect the radius or ulna
to the humerus or pectoral girdle.
 Again, we have flexors, extensors and
rotators.

Flexors
Biceps brachii
 Brachialis
 Brachioradialis

Extensor

Triceps brachii
Rotators
Supinator
 Pronator teres
 Pronator quadratus

Muscles that move the hand






Flexors
Anterior side
Flexor carpi radialis
Flexor carpi ulnaris
Palmaris longus
Flexor digitorum
profundus






Extensors
Posterior side
Extensor carpi radialis
longus
Extensor carpi radialis
brevis
Extensor carpi ulnaris
Extensor digitorum
Muscles of the abdominal wall
External oblique
 Internal oblique
 Transversus abdominis
 Rectus abdominis

Muscles of the pelvic outlet


Pelvic diaphragm
Levator ani




Urogenital diaphragm
Superficial transversus
perinei
Bulbospongiosus
Ischiocavernosus
Muscles that move the thigh
Anterior group
 Psoas major
 Iliacus
Posterior group
 Gluteus maximus
 Gluteus medius
 Gluteus minimus
 Tensor fasciae latae
Muscles that move the leg
Flex the knee
 Biceps femoris
 Semitendinosus
 Semimembranosus
 Sartorius
Extend the knee
 Quadriceps femoris group,
consisting of:
 Rectus femoris
 Vastus lateralis
 Vastus medialis
 Vastus intermedius
Muscles that move the foot
Dorsal flexors
 Tibialis anterior
 Fibularis
 Extensor digitorum
Plantar flexors
 Gastrocnemius
 Soleus
 Flexor digitorum longus