Back Muscles

Iliocostalis Lumborum - Origin

L1-L4 transverse processes; angles of ribs 5-12

Iliocostalis Lumborum - Insertion

Ventral edge of iliac crest; dorsal PSIS and iliac crest

Iliocostalis Lumborum - Peripheral Innervation

Posterior rami of spinal nerves

Iliocostalis Lumborum - Action

Back extension; creates posterior shear forces to counteract anterior shear forces; side bending

Longissimus Thoracis - Origin

L1-L5 accessory processes; T1-T12 transverse processes and ribs 4-12

Longissimus Thoracis - Insertion

Ventral surface PSIS; L1-L4 caudal tendons form lumbar intermuscular aponeurosis; L1-L5 spinous processes; sacrum and ilium

Longissimus Thoracis - Peripheral Innervation

Posterior rami of spinal nerves

Longissimus Thoracis - Action

Back extension; creates posterior shear forces to counteract anterior shear forces; side bending

Lumbar Multifidus - Origin

L1-L5 spinous processes and laminae

Lumbar Multifidus - Insertion

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

Lumbar Multifidus - Peripheral Innervation

Posterior rami of spinal nerves

Lumbar Multifidus - Action

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

Multifidus (Cervical and Thoracic) - Origin

Cervical and thoracic spinous processes

Multifidus (Cervical and Thoracic) - Insertion

Cervical articular and transverse processes; thoracic transverse processes

Multifidus (Cervical and Thoracic) - Peripheral Innervation

Posterior rami of spinal nerves

Multifidus (Cervical and Thoracic) - Action

Extension and contralateral rotation

Quadratus Lumborum - Origin

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

Quadratus Lumborum - Insertion

Iliolumbar ligament and adjacent portion of iliac crest

Quadratus Lumborum - Peripheral Innervation

Anterior branches of T12 and L1-L4 nerves

Quadratus Lumborum - 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 - Origin

Angle of lower 6 ribs

Iliocostalis Thoracis - Insertion

Angles of upper 6 ribs; transverse process of C7

Iliocostalis Thoracis - Peripheral Innervation

Posterior rami of spinal nerves

Iliocostalis Thoracis - Action

Back extension; lateral flexion

Iliocostalis Cervicis - Origin

Angles of ribs 3-6

Iliocostalis Cervicis - Insertion

Transverse processes of C4-C6

Iliocostalis Cervicis - Peripheral Innervation

Posterior rami of spinal nerves

Iliocostalis Cervicis - Action

Back extension; lateral flexion

Longissimus Cervicis - Origin

Upper 4 or 5 thoracic transverse processes

Longissimus Cervicis - Insertion

Posterior tubercles of transverse processes of C2-C6

Longissimus Cervicis - Peripheral Innervation

Posterior rami of spinal nerves

Longissimus Cervicis - Action

Extension; lateral flexion of spine/head

Longissimus Capitis - Origin

Lower 3 or 4 cervical articular processes

Longissimus Capitis - Insertion

Mastoid process

Longissimus Capitis - Peripheral Innervation

Posterior rami of spinal nerves

Longissimus Capitis - Action

Extension; lateral flexion of spine/head

Spinalis Thoracis - Location

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

Spinalis Thoracis - Peripheral Innervation

Posterior rami of spinal nerves

Spinalis Thoracis - Action

Back extension (well developed in thoracic region only)

Spinalis Cervicis - Location

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

Spinalis Cervicis - Peripheral Innervation

Posterior rami of spinal nerves

Spinalis Cervicis - Action

Back extension (well developed in thoracic region only)

Spinalis Capitis - Location

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

Spinalis Capitis - Peripheral Innervation

Posterior rami of spinal nerves

Spinalis Capitis - Action

Back extension (well developed in thoracic region only)