Iliocostalis Thoracis Anatomy

Iliocostalis Thoracis O, I, A

Origin:  Superior borders of the angles of the lower six ribs, medial to the proximal tendon of the iliocostalis lumborum
Insertion:  Superior borders of the angles of the upper six ribs and the posterior aspect of the transverse process of C7
Actions:  Extension of the thoracic spine, lateral flexion of the thoracic spine
Innervation:  Dorsal primary rami of T1 to T12
Blood Supply: Dorsal rami of the posterior intercostal arteries

Primary Actions of the Iliocostalis Thoracis

1.  Extension of the thoracic spine when acting bilaterally

Agonists:

  • Iliocostalis Cervicis
  • Iliocostalis Lumborum
  • Longissimus Cervicis
  • Longissimus Thoracis
  • Spinalis Thoracis
  • Semispinalis Cervicis
  • Semispinalis Thoracis
  Antagonists:
  • Rectus Abdominis

2.   Lateral flexion of the thoracic spine when acting unilaterally

  Agonists:

  • Iliocostalis Cervicis
  • Iliocostalis Lumborum
  • Longissimus Cervicis
  • Longissimus Thoracis
  • External Oblique
  • Internal Oblique
  Antagonists: Same muscles on contralateral side

  • Iliocostalis Cervicis
  • Iliocostalis Lumborum
  • Longissimus Cervicis
  • Longissimus Thoracis
  • External Oblique
  • Internal Oblique

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