Back muscles

attachments, action, and innervation

Trapezius (action)

responsible for elevation, retraction, and depression of scapula; also suspends upper limb

Trapezius (attachment)

• superior attachment: EOP, nuchal ligament

• inferior medial attachment: spinous process of C7-T12

• lateral attachment: clavicle, acromion process, and spine of the scapula

Trapezius (innervation)

innervated by the spinal accessory nerve (aka cranial nerve 11)

latissimus dorsi (action)

responsible for adduction of humerus, shoulder extension (GH joint), and internal rotation of the humerus

latissimus dorsi (attachments)

• attaches to the spinous process T7-T12, thoracolumbar fascia, iliac crest, ribs 9-12 and attach to the floor of the intertubercular groove

latissimus dorsi (innervation)

thoracodorsal nerve

levator scapulae (action)

responsible for extension of the cervical spine bilaterally, lateral flexion of cervical spine unilaterally, elevate scapula, and inferior rotation of scapula

levator scapulae (attachments)

• proximal attachment: transverse process of C1-C4

• distal attachment: medial border of the scapula superior to the root of the spine

levator scapulae (innervation)

dorsal scapular nerve

serratus posterior (action)

superior: inhalation (elevate ribs)

inferior: exhalation (depress ribs)

serratus posterior (attachments)

• superior muscle: transverse process C7-T3 to the superior and inferior border of ribs 2-5

• inferior muscle: spinous process of T11-L2 to ribs 9-12

serratus posterior (innervation)

intercostal nerves

Rhomboid major and minor (action)

responsible for retracting the scapula, inferiorly rotate scapula

rhomboid major and minor (attachments)

minor: nuchal ligament and spinous process of C7 and T1 to the medial border of the scapula (superior to major)

major: spinous process of T2-T5 to medial border of scapula (inferior to minor)

rhomboid major and minor (innervation)

dorsal scapular nerve

splenius capitis and cervicis (action)

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

bilaterally: extend head and neck

splenius capitis and cervicis (attachments)

• capitis: nuchal ligament and spinous process of C7-T6 to the mastoid process of temporal bone and lateral 3rd of superior nuchal line of occipital bone

• cervicis: nuchal ligament and spinous process of C7-T6 to tubercles of transverse processes of C1-C3 or C4

splenius capitis and cervicis (innervation)

posterior rami

erector spinae muscles (action)

• bilaterally: extend vertebral column and head

• unilaterally: lateral flexion

erector spinae (attachments)

• all come from the broad tendon from the posterior part of iliac crest (thoracolumbar fascia), posterior surface of sacrum, sacro-iliac ligaments, sacral and inferior lumbar spinous processes, and supraspinous ligament

• iliocostalis: run superiorly to angles of lower ribs and cervical transverse processes

• longissimus: run superiorly to ribs between tubercles and angles to transverse processes in thoracic and cervical regions and to mastoid process of temporal bone

• spinalis: run superiorly to spinous processes in upper thoracic region and to cranium

erector spinae muscles (innveration)

posterior rami

semispinalis (thoracis, cervicis, and capitis) (action)

extends the head and thoracic and cervical regions of vertebral column and rotates them contralaterally

semispinalis (thoracis, cervicis, capitis) (attachments)

• transverse processes of C4-T10 to the occipital bone and spinous processes in the upper thoracic and cervical regions, spanning four to six segments

semispinalis (thoracis, cervicis, capitis) (innervation)

posterior rami

multifidus (action)

unilateral contraction rotates to contralateral side; stabilizes vertebrae during local mvmts of vertebral column

multifidus (attachments)

• sacrum to TP and SP of adjacent vertebrae from sacrum to cervical spine

multifidus (innveration)

posterior rami

rotatores (action)

proprioception; stabilize vertebrae; assist with extension and rotation

rotatores (attachments)

• brevis: TP of one vertebrae and connects to TP or SP of vertebrae immediately above

• longus: TP of one vertebrae and connects to TP or SP of vertebrae 2 above

rotatores (innveration)

posterior rami

interspinales (action)

extension and rotation of vertebral column

interspinales (attachments)

superior surface of SP of cervical and lumbar vertebrae; inferior surfaces of spinous processes of vertebrae superior to vertebrae of origin

SP to SP

interspinales (innervation)

posterior rami

intertransversarii (action)

lateral flexion of vertebral column; stabilize vertebral column bilaterally

intertransversarii (attachments)

• transverse process of cervical and lumbar vertebrae; transverse process of adjacent vertebrae

• TP to TP

intertransversarii (innervation)

posterior rami

levatores costarum (action)

elevate ribs (respiration); lateral flexion of vertebral column

levatores costarum (attachments)

• tips of transverse processes of C7 and T1-T11; insert on rib between tubercle and angle

levatores costarum (innervation)

posterior rami

rectus capitis posterior major (attachments)

SP of C2 to the lateral part of the inferior nuchal line of occipital bone

rectus capitis posterior minor (attachments)

posterior tubercle on the posterior arch of C1 to the medial 3rd of the inferior nuchal line

obliquus capitis inferior (attachments)

SP of C2 to the TP of C1

*NOT attached to cranium but called capitis

obliquus capitis superior (attachments)

TP of C1 to the occipital bone between superior and inferior nuchal lines

suboccipital region (innervation)

• suboccipital nerve (C1 dorsal ramus)

• greater occipital nerve (C2 dorsal ramus)

suboccipital region (action)

rotate head on C1 and C2; extend head on C1; proprioception