Deep (intrinsic) muscles of the back

Question 1

Erector spinae (iliocostalis, longissimus, spinalis)

Answer 1

Origin: iliac crest, sacrum, transverse and spinous processes of vertebrae and supraspinal ligament

Insertion: angles of the ribs, transverse and spinous processes of vertebrae, posterior aspect of the skull

Action: extends and laterally bends the trunk, neck and head

Nerve: segmentally innervated by dorsal primary rami of spinal nerves C1-S5

Artery: supplied segmentally by: deep cervical a., posterior intercostal aa., subcostal aa., lumbar aa.

Question 2

Multifidus

Answer 2

Origin: sacrum and the transverse processes of the C2-L5 vertebrae

Insertion: spinous processes of the vertebrae superior to their origins

Action: extension, ipsilateral flexion and contralateral rotation of the spine

Nerve: dorsal primary rami of the spinal nerves (C1-L5)

Artery: deep cervical a., posterior intercostal a., subcostal a., lumbar a.

Question 3

Iliocostalis

Answer 3

Origin: sacrum, iliac crest

Insertion: transverse processes of the upper lumbar vertebrae, the 6-12 ribs, thoracolumbar fascia, upper angle of 1-6 ribs

Action: extension, abduction and rotation of the spine

Nerve: dorsal rami of thoracic nerves, L1, L2, L3

Artery: deep cervical a., posterior intercostal a., lumbar a.

Question 4

Longissimus

Answer 4

Origin: sacrum, iliac crest, spinous processes of lumbar vertebrae, transverse processes of the lower thoracic vertebrae

Insertion: 2-12 ribs, costal processes of the lumbar vertebrae, transverse processes of the thoracic vertebrae

Action: extension and lateral flexion of the trunk, neck, and head

Nerve: dorsal primary rami of spinal nerves (C1-S1)

Artery: deep cervical a., posterior intercostal a., lumbar a.

Question 5

Spinalis

Answer 5

Origin: spinous processes at the inferior vertebral levels of T10-L3

Insertion: spinous processes at the superior vertebral levels of T2-T8 and base of the skull

Action: support, extension and lateral flexion of the spine

Nerve: dorsal primary rami of the thoracic nerve and the upper lumbar spinal nerves (T2-L3)

Artery: deep cervical a., posterior intercostal a., lumbar a.

Question 6

Semispinalis

Answer 6

Origin: C4-T12 transverse processes

Insertion: occipital bone, C2-C5 spinous processes, C6-T4 spinous processes

Action: Extension, bends to same side, rotates to opposite side

Nerve: spinal nn. (dorsal rami)