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
-
Iliocostalis cervicis
-
Iliocostalis thoracis
- Iliocostalis lumborum
-
Longissimus cervicis
-
Spinalis thoracis
-
Semispinalis cervicis
-
Semispinalis thoracis
-
Rectus Abdominis
2. Lateral flexion of the thoracic spine when acting unilaterally
-
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
-
Iliocostalis lumborum
-
Spinalis thoracis
-
Rectus Abdominis
4. Lateral flexion of the lumbar spine when acting unilaterally
-
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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