OIIA Back muscles

trapezius origin

medial third of superior nuchal line, external occipital protuberance, nuchal ligament, spinous process of C7-T12 vertebrae

trapezius insertion

lateral third of clavicle, acromion and spine of scapula

trapezius innervation

Spinal accessory nerve (CN XI; motor fibers) and C3, C4 spinal nerves (pain and proprioceptive fibers)

trapezius action

superior part elevates, inferior part depresses, and middle part retracts scapula; descending and ascending parts act together to rotate glenoid cavity superiorly.

latissimus dorsi origin

Spinous processes of inferior six thoracic vertebrae, thoracolumbar fascia, iliac crest, and inferior three or four ribs

lattismus dorsi attachment

Floor of intertubercular sulcus (groove) of humerus

latissimus dorsi innervation

Thoracodorsal nerve (C6, C7, C8)

latissimus dorsi action

Extends, adducts, and medially rotates shoulder joint; raises body toward arms during climbing

levator scapulae origin

Posterior tubercles of transverse processes of C1-C4 vertebrae

levator scapulae insertion

Superior part of medial border of scapula

levator scapulae innervation

Dorsal scapular (C5) and cervical (C3, C4) spinal nerves

levator scapulae action

elevates scapula and tilts glenoid cavity inferiorly by rotating scapula

rhomboid minor origin

nuchal ligament; spinous processes of C7 and T1 vertebrae

rhomboid major origin

spinous processes of T2-T5 vertebrae

rhomboid minor insertion

triangular area at medial end of scapular spine

rhomboid major insertion

medial border of scapula from level of spine to inferior angle

rhomboid major and minor innervation

Dorsal scapular nerve (C4, C5)

rhomboid major and minor action

Retracts scapula and rotates glenoid cavity inferiorly; fix scapula to thoracic wall

rectus capitis posterior major origin

spinous process of the C2 vertebra

rectus capitis posterior major insertion

lateral part of the inferior nuchal line of the occipital bone

lateral part of the inferior nuchal line of the occipital bone innervation

dorsal rami

rectus capitis posterior major action

extends (bilaterally concentric) and rotates ipsilaterally (unilateral concentric) head and lateral flexion ipsilaterally (unilateral concentric) on upper cervical spine

rectus capitis posterior minor origin

posterior tubercle on the posterior arch of the C1 vertebra

rectus capitis posterior minor insertion

medial third of the inferior nuchal line.

rectus capitis posterior minor innervation

dorsal rami

rectus capitis posterior minor action

extend the head on C1 and rotate the head and the C1 on C2 vertebrae

obliquus capitis inferior origin

spinous process of the C2 vertebra

obliquus capitis inferior insertion

transverse process of the C1 vertebra

obliquus capitis inferior innervation

dorsal rami

obliquus capitis inferior action

extends (bilaterally concentric) and rotates ipsilaterally (unilateral concentric) head and lateral flexion ipsilaterally (unilateral concentric) on upper cervical spine

 

Obliquus capitis superior origin

transverse process of C1

obliquus capitis superior insertion

occipital bone between the superior and the inferior nuchal lines.

obliquus capitis superior innervation

dorsal rami

obliquus capitis superior action

extend the head on C1 and rotate the head and the C1 on C2 vertebrae

splenius capitis action

Unilaterally: laterally flexes neck and rotates head to side of active muscles

bilaterally: extend head and neck

splenius cervicis action

Unilaterally: laterally flexes neck and rotates head to side of active muscles

bilaterally: extend head and neck

ilocostalis action

bilaterally: extend vertebral column and head; as back is flexed, control movement by gradually lengthening their fibers

unilaterally: laterally flex vertebral column

spinalis action

bilaterally: extend vertebral column and head; as back is flexed, control movement by gradually lengthening their fibers

unilaterally: laterally flex vertebral column

longissimus action

bilaterally: extend vertebral column and head; as back is flexed, control movement by gradually lengthening their fibers

unilaterally: laterally flex vertebral column

semispinalis action

Extends head and thoracic and cervical regions of vertebral column and rotates them contralaterally

mutifidus action

Unilateral contraction rotates to contralateral side; stabilizes vertebrae during local movements of vertebral column

rotator muscles action

May function as organs of proprioception; possibly stabilize vertebrae and assist with local extension and rotatory movements of vertebral column

Interspinales action

Aid in extension and rotation of vertebral column

Intertransversarii action

Aid in lateral flexion of vertebral column; acting bilaterally, stabilize vertebral column

sternocleidomastoid origin

Lateral surface of mastoid process of temporal bone and lateral half of superior nuchal line

sternocleidomastoid insertion

Sternal head: anterior surface of manubrium of sternum

 

Clavicular head: superior surface of medial third of clavicle

sternocleidomastoid innervation

Spinal accessory nerve (CN XI; motor), C2 and C3 nerves (pain and proprioception)

sternocleidomastoid action

Unilateral contraction: tilts head to same side (i.e., laterally flexes neck) and rotates it so face is turned superiorly toward opposite side

 

Bilateral contraction: (1) extends neck at atlantooccipital joints, (2) flexes cervical vertebrae so that chin approaches manubrium, or (3) extends superior cervical vertebrae while flexing inferior vertebrae so chin is thrust forward with head kept level

 

With cervical vertebrae fixed, may elevate manubrium and medial end of clavicles, assisting pump-handle action of deep respiration

anterior scalene origin

Anterior tubercles of transverse processes of C3-C6 vertebrae

anterior scalene insertion

1st rib

anterior scalene innervation

Cervical spinal nerves C4-C6

anterior scalene action

Forced inspiration, elevates 1st rib

middle scalene origin

Posterior tubercles of transverse processes of C4-C7 vertebrae

middle scalene insertion

Superior surface of 1st rib; posterior to groove for subclavian artery

middle scalene innervation

Anterior rami of cervical spinal nerves

middle scalene action

Flexes neck laterally; forced inspiration, elevates 1st rib

posterior scalene origin

Posterior tubercles of transverse processes of C4-C6 vertebrae

posterior scalene insertion

External border of 2nd rib

posterior scalene innervation

Anterior rami of cervical spinal nerves C7 and C8

posterior scalene action

Flexes neck laterally; elevates 2nd rib during forced inspiration

Pectoralis major origin

Clavicular head: anterior surface of medial half of clavicle

 

Sternocostal head: anterior surface of sternum, superior six costal cartilages, aponeurosis of external oblique muscle

Pectoralis major insertion

Lateral lip of intertubercular sulcus (groove) of humerus

Pectoralis major innervation

Lateral and medial pectoral nerves, clavicular head (C5, C6), sternocostal head (C7, C8, T1)

Pectoralis major action

Adducts and medially rotates shoulder joint, draws scapula anteriorly and inferiorly

Acting alone, clavicular head flexes shoulder joint and sternocostal head and extends it from the flexed position.

Pectoralis minor origin

3rd-5th ribs near their costal cartilages

Pectoralis minor insertion

Medial border and superior surface of coracoid process of scapula

Pectoralis minor innervation

Medial pectoral nerve (C8, T1)

Lateral pectoral nerve (variable)

Pectoralis minor action

Stabilizes scapula by drawing inferiorly and anteriorly against thoracic wall

serratus anterior origin

External surfaces of lateral parts of 1st-8th ribs

serratus anterior insertion

Anterior surface of entire medial border of scapul

serratus anterior innervation

Long thoracic nerve (C5, C6, C7)

serratus anterior action

Protracts scapula and holds it against thoracic wall; rotates scapula

subscapularis origin

Subscapular fossa (most of anterior surface of scapula)

subscapularis insertion

Lesser tubercle of humerus

subscapularis innervation

Upper and lower subscapular nerves (C5, C6, C7)

subscapularis action

Medially rotates and adducts shoulder joint and acts with other rotator cuff musclesb

deltoid origin

Lateral third of clavicle; acromion and spine of scapula

deltoid insertion

Deltoid tuberosity of humerus

deltoid innervation

Axillary nerve (C5, C6)

Deltoid Action

Clavicular (anterior) part flexes and medially rotates shoulder joint; acromial (middle) part abducts shoulder joint; spinal (posterior) part extends and laterally rotates shoulder joint

supraspinatus origin

Supraspinous fossa of scapula

supraspinatus insertion

superior facet of greater tubercle of humerus

supraspinatus innervation

Suprascapular nerve (C4, C5, C6)

supraspinatus action

Initiates and assists deltoid in abduction of shoulder joint and acts with other rotator cuff musclesb

infraspinatus origin

Infraspinous fossa of scapula

infraspinatus insertion

middle facet of greater tubercle of humerus

infraspinatus innervation

Suprascapular nerve (C5, C6)

infraspinatus action

Laterally rotates shoulder joint and acts with other rotator cuff muscles

teres minor origin

Middle part of lateral border of scapula

teres minor insertion

inferior facet of greater tubercle of humerus

teres minor innervation

Axillary nerve (C5, C6)

teres minor action

Laterally rotates shoulder joint and acts with other rotator cuff musclesb

teres major origin

Inferior part of lateral border of scapula and posterior surface of inferior angle of scapula

teres major insertion

Medial lip of intertubercular sulcus of humerus

teres major innervation

Lower subscapular nerve (C5, C6

teres major action

Adducts and medially rotates shoulder joint