Longissimus thoracis
Back
Deep muscle — it lies under other muscles. X-ray makes the muscles over it see-through.
- Origin
- Sacrum, iliac crest and transverse processes of the lumbar vertebrae
- Insertion
- Transverse processes of all thoracic vertebrae and the lower nine or ten ribs
- Action
- Extends and laterally flexes the spine
- Nerve supply
- Dorsal rami of the spinal nerves
The largest section of the erector spinae, running from the pelvis to the ribs. It is the main column that holds the spine neutral in squats and deadlifts and extends it in back extensions.