Deep Muscles of the Spine DPR=dorsal primary rami, VPR=ventral primary rami, T=thoracic, C=cervical, L=lumbar

Iliocostalis Lumborum, pars Lumborum

Proximal Attachment

L1-L4 transverse processes

Distal Attachment

Ventral edge of iliac crest

Peripheral Innervation

Posterior rami of spinal nerves

Action

Back extension, creates posterior shear forces to counteract anterior shear forces

Iliocostalis Lumborum, pars Thoracis

Proximal Attachment

Angles of ribs 5-12

Distal Attachment

Dorsal PSIS and iliac crest

Peripheral Innervation

Posterior rami of spinal nerves

Action

Back extension, side bending

Longissimus Thoracis, pars Lumborum

Proximal Attachment

L1-L5 accessory processes

Distal Attachment

Ventral surface PSIS; L1-L4 caudal tendons form lumbar intermuscular aponeurosis

Peripheral Innervation

Posterior rami of spinal nerves

Action

Back extension, creates posterior shear forces to counteract anterior shear forces

Longissimus Thoracis, pars Thoracis

Proximal Attachment

T1-T12 transverse processes and ribs 4-12

Distal Attachment

L1-5 spinous processes, sacrum and ilium

Peripheral Innervation

Posterior rami of spinal nerves

Action

Back extension, side bending

Lumbar multifidus

Proximal Attachment

L1-5 spinous processes and laminae

Distal Attachment

L1-S1 mammillary processes 2, 3, and 4 levels caudal from rostral attachment; deep surface of erector spinae aponeurosis

Peripheral Innervation

posterior rami of spinal nerves

Action

Extension, stabilize/stiffen lumbar spine, neutralize flexion moment during trunk rotation

Multifidus (cervical and thoracic)

Proximal Attachment

Cervical and Thoracic spinous processes

Distal Attachment

Cervical articular and transverse processes; thoracic transverse processes

Peripheral Innervation

Posterior rami of spinal nerves

Action

Extension and contralateral rotation

Quadratus Lumborum

Proximal Attachment

Medial half of rib 12, tips of L1-L4 transverse processes

Distal Attachment

Iliolumbar ligament and adjacent portion of iliac crest

Peripheral Innervation

Anterior Branches of T12 and L1-L4 nerves

Action

Fixes last rib so diaphragm acts more efficiently during inspiration; hikes hip; ipsilateral side bending when pelvis is fixed
Acting bilaterally forms guy wire support to stabilize lumbar spine in frontal plane

Iliocostalis thoracis

Proximal Attachment

Angle of lower 6 ribs

Distal Attachment

Angles of upper 6 ribs, transverse process of C7

Peripheral Innervation

posterior rami of spinal nerves

Action

Back extension, lateral flexion

Iliocostalis cervicis

Proximal Attachment

Angles of ribs 3-6

Distal Attachment

Transverse processes of C4-C6

Peripheral Innervation

posterior rami of spinal nerves

Action

Back extension, lateral flexion

Longissimus cervicis

Proximal Attachment

Upper 4 or 5 thoracic transverse processes

Distal Attachment

Posterior tubercles of transverse processes of C2-C6

Peripheral Innervation

posterior rami of spinal nerves

Action

Extension, lateral flexion of spine/head

Longissimus capitis

Proximal Attachment

Lower 3 or 4 cervical articular processes

Distal Attachment

Mastoid process

Peripheral Innervation

posterior rami of spinal nerves

Action

Extension, lateral flexion of spine/head

Spinalis thoracis

Proximal + Distal Attachment

Spinous process to spinous process as distal as L2 (fibers cross over multiple levels)

Peripheral Innervation

posterior rami of spinal nerves

Action

Back extension (FYI for lab: well developed in thoracic region ONLY)

Spinalis cervicis

Proximal + Distal Attachment

Spinous process to spinous process as distal as L2 (fibers cross over multiple levels)

Peripheral Innervation

posterior rami of spinal nerves

Action

Back extension (FYI for lab: well developed in thoracic region ONLY)

Spinalis capitis

Proximal + Distal Attachment

Spinous process to spinous process as distal as L2 (fibers cross over multiple levels)

Peripheral Innervation

posterior rami of spinal nerves

Action

Back extension (FYI for lab: well developed in thoracic region ONLY)