Longissimus Thoracis Anatomy

Longissimus Thoracis O, I, A

Origin:  Blended with iliocostalis lumborum, from the posterior surfaces of the transverse processes of all the lumbar vertebrae and the thoracolumbar fascia.
Insertion: Tips of the transverse processes of all thoracic vertebrae and lower nine or ten ribs, between the tubercle and angle.
Actions:  Extension and lateral flexion of the thoracic spine, extension and lateral flexion of the lumbar spine
Innervation:  Dorsal primary rami of T1 to L5
Blood Supply: Dorsal rami of the posterior intercostal arteries

Primary Actions of the Longissimus Thoracis

1.  Extension of the thoracic spine when acting bilaterally

Agonists:
  • Iliocostalis cervicis
  • Iliocostalis thoracis
  • Iliocostalis lumborum
  • Longissimus cervicis
  • Spinalis thoracis
  • Semispinalis cervicis
  • Semispinalis thoracis
  Antagonists:
  • Rectus Abdominis

2.  Lateral flexion of the thoracic spine when acting unilaterally

  Agonists:
  • Iliocostalis cervicis
  • Iliocostalis thoracis
  • Iliocostalis lumborum
  • Longissimus cervicis
  • External Oblique
  • Internal Oblique

  Antagonists: Same muscles on contralateral side

  • Iliocostalis cervicis
  • Iliocostalis thoracis
  • Iliocostalis lumborum
  • Longissimus cervicis
  • External Oblique
  • Internal Oblique

3. Extension of the lumbar spine when acting bilaterally

  Agonists:
  • Iliocostalis lumborum
  • Spinalis thoracis
  Antagonists:
  • Rectus Abdominis

4. Lateral flexion of the lumbar spine when acting unilaterally

  Agonists:
  • Iliocostalis lumborum
  • Psoas major
  • Quadratus lumborum
  • External oblique
  • Internal oblique

Antagonists: Same muscles on contralateral side

  • Iliocostalis lumborum
  • Psoas major
  • Quadratus lumborum
  • External oblique
  • Internal oblique

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