intrinsic back muscles

Question 1

(surface layer/intrinsic muscles of back)

Answer 1

splenius cervicis

• *Origin** : nuchal ligament and spinous processes of C7–T6 vertebrae
• *insertion**: tubercles of transverse processes of C1–C3 or C4 vertebrae
  action:
• *Acting alone**: laterally flexes neck and rotates head to side of active muscles
• *Acting together**: extend head and neck
• *innervation**: posterior rami of spinal nerves

Question 2

(surface layer/intrinsic muscles of the back)

Answer 2

Spenius capitis

origin: Ligamentum niche; C7 to T7
Insertion: occipital bone; temporal bone (mastoid process)
action:
Acting alone: laterally flexes neck and rotates head to side of active muscles
Acting together: extend head and neck
Innervation: posterior rami of spinal nerves

Question 3

(Intermediate layer/erector spine)

Answer 3

Illiocostalis

Divided into 3 layers

• *Lumborum**
• *Thoracic**
• *Cervisis**
• *Origin**: arise by tendon from posterior part of iliac crest, posterior surface of sacrum
• *Inserts**: Fibers run superiorly to angles of lower ribs and cervical transverse processes.
• *Action**:
• *Acting bilaterally**: extend vertebral column and head;
• *Acting unilaterally**: laterally flex vertebral column
• *Innervation**: Posterior rami of spinal nerves

Question 4

(intermediate layer/erector spinae)

Answer 4

Longissimus

thoracic

cervicis

capitis

Origin: posterior surface of sacrum, sacral and inferior lumbar spinous processes.

Insertion: transverse processes in thoracic and cervical regions and to mastoid process of temporal bone.

Action:

acting bilaterally: extend vertebral column and head

Acting unilaterally: laterally flex vertebral column (ipsilaterally)

Innervation: Posterior rami of spinal nerves

Question 5

(intermediate layer/erector spinae)

Answer 5

Spinalis

thoracic

cervicis

captis

most medial of intermediate layer

origin: arises from half of the vertebral column

insertion: spinous processes of thoracic, cervicis or occipital bone (cap)

action:

bilateral: extend vertebral column and head

unilaterally: laterally flex vertebral column

innervation: posterior rami of spinal nerves

Question 6

(third layer) (transversospinales group)

Answer 6

semispinalis (thoracic, cervicis, capitis)

origin: transverse processes of C4–T10 vertebrae
Insertion: spinous processes of thorax, cervic, and occipital bone
Action:
extends head and thoracic and cervicals regions of vertebral column and rotates them contralaterally

Innervation: posterior rami of spinal nerves

Question 7

(third layer)

Answer 7

rotators

incredibly small, adjust subtily

Origin: transverse processes of vertebra

insertion: junction of lamina and transverse process or spinous process of vertebra

action: possibly stabilize vertebrae and assist with local extension and rotatory movements of vertebral column

innervation: posterior rami of spinal nerves

Question 8

(third layer)

Answer 8

multifidus

even shorter distance, runs from transverse process up to facets

innervation: posterior rami of spinal nerves

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