Trunk (thorax, abdomen, back)
Longissimus Thoracis
Musculus longissimus thoracis
- Origin
- Sacrum, iliac crest and spinous processes of the lumbar vertebrae via the thoracolumbar fascia
- Insertion
- Transverse processes of all thoracic vertebrae and the lower ribs
- Function
- Primary extensor of the spine along the entire length of the trunk; unilateral contraction produces lateral flexion
- Innervation
- Dorsal rami of the thoracic and lumbar spinal nerves
- Movement & chain
- Largest and most powerful part of erector spinae; essential for keeping the trunk upright during lifting and for controlling trunk flexion (eccentrically)
- Palpation
- Felt as a broad, vertical muscle mass along either side of the spinous processes in the lumbar and lower thoracic region, especially well activated during resisted back extension
- Clinical
- Overuse of this muscle part is a frequent cause of nonspecific low back pain, particularly after asymmetric lifting or bending work
- Segmental innervation
- Dorsal rami T1-L5
- In clinical practice
- Important point of attention in back-care education and lifting-technique instruction; tension in this muscle part is often palpable in patients with postural low back complaints.
- Region in the model
- Trunk (thorax, abdomen, back)