Acting alone they help rotate head

Acting together extend head and neck

Innervation of Erector Spinae muscles

(Illocostalis, Longissimus, Spinalis)

Posterior iliac crest or posterior sacrum

Spinous processes and supraspinous ligaments

Angles of lower ribs or transverse processes of cervical vertebrae

Depends which one (lumborum, thoracis, cervicis)

Transverse process in thoracic and cervical regions, mastoid process of occipital bone

depends on if thoracis, cervicis, capitis

Spinous process of upper thoracic region and skull

(depends if thoracis,cervicis, capitis)

Semispinalis 4-6 segments

Multifidus 2-4 segments

rotatores brevis 1 segment

rotatores longus 2 segments

upper fibers elevate scapula

middle fibers retract scapula

lower fibers pull medial border of scapula downward

all together increase abduction range of humerus by rotating scapula upward

medially rotates arm

stabilizes shoulder

Anterior surface bicipital clavicle,

Manubrium sternum,

upper six costal cartilages

Depresses point of shoulder,

Can elevate ribs of origin (3-5) if the scapula is fixed

Depresses clavicle

Steadies clavicle during shoulder girdle movements

Outer surface of upper eight ribs

fascia covering spaces between ribs

Protracts scapula and pectoral girdle

Rotates scapula upward (especially during humeral abduction)

Anterior border of clavicle,

acromion process,

lower lip of crest of the scapular spine

Intermediate (strong abductor of arm)

Anterior fibers (flex and medially rotate arm)

Posterior fibers (extend and laterally rotate arm)

Medially rotates arm

Adducts arm,

Stabilizes shoulder joint

Laterally rotates arm,

Stabilizes joint

Greater tuberosity of humerus

Capsule of shoulder joint