The longissimus is a deep muscle of the back. It lies between the iliocostalis and spinalis within the erector spinae complex, and can be divided into three parts – thoracic, cervicis, and capitis.
- Attachments: Arises from the lower thoracic and lumbar vertebrae, sacrum, posterior aspect of the iliac crest, and the sacroiliac and supraspinous ligaments. It attaches to the lower ribs, the transverse processes of C2 – T12, and the mastoid process of the skull.
- Actions: Acts unilaterally to laterally flex the vertebral column. Acts bilaterally to extend the vertebral column and head.
- Innervation: Posterior rami of the spinal nerves.
- Blood Supply:
- Longissimus thoracic receives blood supply from the dorsal branches of posterior intercostal and sacral arteries.
- Longissimus cervicis and capitis receive blood from the transverse cervical, occipital, vertebral, and deep cervical arteries.