Extrinsic and Intrinsic Back Muscles

Question 1

Serratus posterior superior

Answer 1

extrinsic, intermediate

attachments- from spinous processes of C7-T3 to inferior borders of ribs 2-5

function- proprioception of thoracic wall

innervation- intercostal nn. (T1-4)

Question 2

Serratus posterior inferior

Answer 2

extrinsic, intermediate

attachments- from spinous processes of T11-L2 to inferior borders of ribs 9-12

function- proprioception of thoracic wall

innervation- intercostal nn. (T9-12)

Question 3

Erector spinae

Answer 3

intrinsic, intermediate

attachments- from TLF attached to the sacrum, iliac crest, spinous processes L5-T11, supraspinous lig., angles of ribs to costal angles (iliocostalis), ribs & transverse processes (longissimus), and spinous processes (spinalis)

1. Spinalis: thoracis, cervicis, capitis (represented as semispinalis capitis)
2. Longissimus: capitis, cervicis, thoracis
3. Iliocostalis: cervicis, thoracis, lumborum

actions- extension & lateral flexion of the vertebral column

innervation- lateral branch or dorsal rami spinal nn.

Question 4

Semispinalis

Answer 4

intrinsic, deep

(transversospinales group)

attachments- from transverse processes to distant superior spinous processes
1. Semispinalis: capitis, cervicis, thoracis

actions- extension & contralateral rotation of the vertebral column

innervation- dorsal rami of spinal nn.

Question 5

Multifidus

Answer 5

intrinsic, deep

(transversospinales group)

attachments- from sacrum, posterior SI ligament, posterior iliac spine, transverse processes to more superior spinous processes

1. Multifidus: sacral, lumbar, thoracic, cervical

actions- extension & contralateral rotation of the vertebral column

innervation- dorsal rami of spinal nn.

Question 6

Rotatores

Answer 6

intrinsic, deep

(transversospinales group)

attachments- transverse to spinous process of vertebra above (1-2 levels)

rotatores longus and brevis

actions- extension & contralateral rotation of the vertebral column

innervation- dorsal rami of spinal nn.

Question 7

Interspinales

Answer 7

intrinsic, deep

attachments- between spinous processes of adjacent vertebrae

cervical (6), thoracic (2-3), lumbar (4)

action- extension of spine, proprioception

innervation- dorsal rami of spinal nn.

Question 8

Intertransversarii

Answer 8

intrinsic, deep

attachments- between the transverse processes of adjacent vertebrae

action- lateral flexion of spine, proprioception

innervation- dorsal rami of spinal nn.

Question 9

Splenius cervicis

Answer 9

intrinsic, superficial

attachments: from spinous processes of T3-T6 to posterior tubercles of transverse processes of C1-3
actions: extension, lateral flexion, ipsilateral rotation
innervation: dorsal rami of spinal nerves

Question 10

Splenius capitis

Answer 10

intrinsic, superficial

attachments: from ligamentum nuchae and spinous processes T4-C7 to the mastoid process
actions: extension, lateral flexion, ipsilateral rotation
innervation: dorsal rami of spinal nerves

Question 11

Latissimus dorsi

Answer 11

(C6-8)

attachments- from lower thoracic spinous processes, thoracolumbar fascia & iliac crest to the floor of the intertubercular sulcus of the humerus

actions- adduction, extension & medial rotation of humerus

innervation- THORACODORSAL NERVE

Question 12

Levator scapulae

Answer 12

(C4-5)

attachments- from transverse processes of C1-C4 to the superior angle & superomedial border of the scapula

actions- elevation & downward rotation of the scapula

innervation- DORSAL SCAPULAR NERVE (sensory: direct branches of C3-4)

Question 13

Rhomboids

Answer 13

(C4-5)

attachments- major: from spinous processes T2-5; minor: from ligamentum nuchae & spinous processes C7-T1 to the medial border of the scapula

actions- scapular retraction, elevation (upper) & downward rotation

innervation- DORSAL SCAPULAR NERVE (sensory: direct branches of C3-4)

Question 14

Trapezius

Answer 14

(Accessory n. [CN XI] motor; C3-4 sensory)

attachments- from the superior nuchal line, external occipital protuberance, ligamentum nuchae, & cervical & thoracic spinous processes to the clavicle, acromion & scapular spine

actions- scapular elevation (upper), depression (lower), retraction (middle) & upward rotation (upper & lower)

innervation- ACCESSORY NERVE (CN XI; motor) & C3-4 (sensory)