Deep Back Muscles

Front 1

Intersegmental muscles (of the deep back)

Back 1

Short muscles that span a single intervertebral joint (segment).

Contribute to fine control of vertebral movement.

Important for proprioception (sense of position) because of high proportion of muscle spindles—specialized sensory fibers that register muscle length and velocity

Front 2

Clinical Correlation Intersegmental muscles:

Back 2

Because their fibers are very short, intersegmental muscles are
susceptible to strain and are implicated in many cases of back and neck pain.

Front 3

Multisegmental muscles (of the deep back)

Back 3

Span multiple intervertebral joints (segments).

Formed by the fusion of intersegmental muscles during embryonic development.

Multisegmental muscles provide forceful extension of the vertebral column, maintain posture, and contribute to rotation and lateral flexion of the torso, head, and neck.

Front 4

Bilateral contraction (of the deep back)

Back 4

Right and left side muscles contract simultaneously.

Lateral flexion and rotational actions cancel out, resulting in pure extension.

Front 5

Unilateral contraction (of the deep back)

Back 5

Muscle contracts on one side only.

Primarily lateral flexion and rotation result.

Front 6

Splenius capitis and cervicis mm Origin:

Back 6

Origin: Ligamentum nuchae and T1–T4 spinous processes

Front 7

Splenius capitis and cervicis mm Insertion:

Back 7

Insertion: Mastoid process and superior nuchal line (capitis portion)
C1–C4 transverse processes (cervicis portion)

Front 8

Splenius capitis and cervicis mm Actions:

Back 8

Actions: Unilateral: lateral flexion and ipsilateral rotation of head/neck
Bilateral: extension of head/neck

Front 9

Erector spinae muscle group (major postural muscle group) Origin:

Back 9

Origin: Common tendon of origin from posterior iliac crest, dorsal sacrum, and
lumbar spinous processes; additional slips originate along the axial
skeleton.

Front 10

Iliocostalis m. (Erector Spinae group) Insertion:

Back 10

Insertion: angles of ribs (lumborum and thoracis) and cervical
transverse processes (cervicis)

Front 11

Longissimus m. (Erector Spinae group) Insertion:

Back 11

Insertion: thoracic transverse processes and adjacent ribs
(thoracis), cervical transverse processes (cervicis), mastoid process
(capitis).

Front 12

Spinalis m. (Erector Spinae group) Insertion:

Back 12

Insertion: upper thoracic spinous processes (thoracis); cervical
spinous processes and ligamentum nuchae (cervicis); occipital bone
between nuchal lines (capitis, usually fused with semispinalis capitis)

Front 13

Erector spinae muscle group Actions:

Back 13

Actions: Unilateral: lateral flexion and ipsilateral rotation of trunk and head/neck
Bilateral: extension of trunk and head/neck

Front 14

Transversospinalis group Origin:

Back 14

Dorsal sacrum and posterior iliac crest, lumbar mamillary processes,
cervical and thoracic transverse processes.

Front 15

Transversospinalis group Insertion:

Back 15

Insertion: Spinous processes and occipital bone.

Front 16

Semispinalis cervicis (Transversospinalis group):

Back 16

From upper thoracic transverse processes to
upper cervical spinous processes as far as C2 (axis).

Spans 4–6 segments, best defined in cervical region.

Front 17

Semispinalis capitis (Transversospinalis group):

Back 17

From cervical transverse processes to
occipital bone; a major extensor of the head.

Spans 4–6 segments, best defined in cervical region.

Front 18

Multifidus lumborum
(Transversospinalis group):

Back 18

2–4 segments, best defined in lumbar region.

Dorsal sacrum and lumbar mamillary
processes to lumbar and lower thoracic spinous processes.

Front 19

Rotatores longus
(Transversospinalis group):

Back 19

Span 2 segments.

Best defined in thoracic region.

Front 20

Rotatores brevis
(Transversospinalis group):

Back 20

Span 1 segment.


Best defined in thoracic region.

Front 21

Transversospinalis group Actions:

Back 21

Unilateral: lateral flexion, contralateral rotation of trunk, head/neck.
Bilateral: extension of trunk and head/neck

Front 22

Levatores costarum m. Origin:

Back 22

Origin: Transverse processes of thoracic vertebrae

Front 23

Levatores costarum m. Insertion:

Back 23

Insertion: Superior borders of ribs (1 or 2 segments inferior)

Front 24

Levatores costarum m. Actions:

Back 24

Actions: Elevate ribs, assist lateral flexion

Front 25

Interspinalis m. (pl. interspinales)
(Intersegmental muscle):

Back 25

between adjacent spinous processes in the cervical and lumbar regions.

Front 26

Intertransverse m. (pl. intertransversarii)
(Intersegmental muscle):

Back 26

between adjacent transverse processes in the cervical and lumbar regions. Note: in the cervical region, anterior and posterior intertransversarii attach to the anterior and posterior tubercles and are separated by the cervical spinal nerves.

Front 27

Clinical correlation Intersegmental mm.

Back 27

Clinical Correlation: Automobile collisions can cause flexion-extension syndrome, or
whiplash. Rapid movement of the head from hyperextension to hyperflexion can tear cervical
intersegmental muscles and sprain cervical ligaments. This produces the characteristic syndrome of tenderness (due to inflammation), stiffness (due to sustained recruitment of uninjured muscles), and radiating pain.

Front 28

Thoracolumbar fascia

Back 28

the investing fascia of the intrinsic back muscles in lower thoracic
and lumbar regions.

Front 29

Posterior layer (Thoracolumbar fascia):

Back 29

attaches to the vertebral spinous processes. This layer is thin in the
thoracic region but forms a dense aponeurosis in the lumbar region.

Front 30

Middle layer (Thoracolumbar fascia):

Back 30

Middle layer: attaches to lumbar transverse processes, iliac crest, and rib 12;
continuous laterally with the aponeurosis of transversus abdominis m.

Front 31

Anterior layer (Thoracolumbar fascia):

Back 31

Anterior layer: the anterior fascia of quadratus lumborum m.

Front 32

Rectus capitis posterior major m. (Suboccipital m.) Origin:

Back 32

Origin: Spinous process of axis (C2)

Front 33

Rectus capitis posterior major m. (Suboccipital m.) Insertion:

Back 33

Insertion: Medial inferior nuchal line

Front 34

Rectus capitis posterior major m. (Suboccipital m.) Actions:

Back 34

Actions: Extension (bilateral) and ipsilateral rotation (unilateral) of head.

Principal functions are postural (fine adjustments) and proprioceptive.

Front 35

Rectus capitis posterior major m. (Suboccipital m.) Innervation:

Back 35

Innervation: dorsal ramus of C1, the
suboccipital n.

Front 36

Rectus capitis posterior minor m.
(Suboccipital m.) Origin:

Back 36

Origin: Posterior tubercle of atlas (C1)

Front 37

Rectus capitis posterior minor m.
(Suboccipital m.) Insertion:

Back 37

Insertion: Inferior nuchal line medial to rectus capitis posterior major m.

Front 38

Rectus capitis posterior minor m.
(Suboccipital m.) Actions:

Back 38

Actions: Extension of head (bilateral)

Front 39

Rectus capitis posterior minor m.
(Suboccipital m.) Innervation:

Back 39

Innervation: dorsal ramus of C1, the
suboccipital n.

Front 40

Obliquus capitis superior m.
(Suboccipital m.) Origin:

Back 40

Origin: Transverse process of atlas (C1)

Front 41

Obliquus capitis superior m.
(Suboccipital m.) Insertion:

Back 41

Insertion: Occipital bone between nuchal lines

Front 42

Obliquus capitis superior m.
(Suboccipital m.) Actions:

Back 42

Actions: Extension of head (bilateral); lateral flexion of head (unilateral)

Front 43

Obliquus capitis superior m.
(Suboccipital m.) Innervation:

Back 43

Innervation: dorsal ramus of C1, the suboccipital n.

Front 44

Obliquus capitis inferior m.
(Suboccipital m.) Origin:

Back 44

Origin: Spinous process of axis (C2)

Front 45

Obliquus capitis inferior m.
(Suboccipital m.) Insertion:

Back 45

Insertion: Transverse process of atlas (C1)

Front 46

Obliquus capitis inferior m.
(Suboccipital m.) Actions:

Back 46

Actions: Ipsilateral rotation of head (unilateral)

Front 47

Obliquus capitis inferior m.
(Suboccipital m.) Innervation:

Back 47

Innervation: dorsal ramus of C1, the suboccipital n.

Front 48

Suboccipital triangle Borders:

Back 48

Rectus capitis posterior major m.

Obliquus capitis superior m.

Obliquus capitis inferior m.

Front 49

Suboccipital triangle floor:

Back 49

Posterior atlanto-occipital membrane and posterior arch of atlas.

Front 50

Suboccipital triangle roof:

Back 50

semispinalis capitis m.

Front 51

Suboccipital Triangle - Vertebral a.

Back 51

Exits transverse foramen of C1.

Curves medially around posterior aspect of lateral mass of atlas.

Pierces posterior atlanto-occipital membrane to enter foramen magnum.

Front 52

Suboccipital Triangle - Suboccipital n. (dorsal ramus of C1)

Back 52

Emerges from center of suboccipital triangle.

Gives muscular branches to suboccipital muscles.

The suboccipital n. has few (if any) sensory fibers and no cutaneous distribution.

Front 53

Occipital a. (branch of external carotid a.):

Back 53

NOT PART OF THE SUBOCCIPITAL TRIANGLE

emerges lateral to obliquus capitis
superior m. and courses superiorly to supply posterior scalp.

Front 54

Greater occipital n. (dorsal ramus of C2):

Back 54

NOT PART OF THE SUBOCCIPITAL TRIANGLE

emerges inferior to obliquus capitis
inferior m. and pierces semispinalis capitis m. (to which it gives some motor fibers) to innervate skin of posterior scalp.

Front 55

Cutaneous innervation of the central back:

Back 55

innervated segmentally by
posterior cutaneous nerves, branches of dorsal primary rami.

Front 56

Cutaneous innervation of the lateral back:

Back 56

Skin of the lateral back is innervated segmentally by lateral cutaneous nerves, branches of ventral primary rami.

Front 57

Intrinsic muscles of the back Blood Supply:

Back 57

Segmental arteries accompanying the dorsal primary rami.

Deep cervical a.: courses deep to semispinalis capitis m.

Vertebral a.: muscular branches to cervical muscles

Front 58

Skin overlying the intrinsic muscles Blood Supply

Back 58

posterior cutaneous arteries, branches of segmental aa.

Front 59

Skin of the lateral back Blood supply

Back 59

lateral cutaneous arteries, branches of the posterior intercostal aa.