The semispinalis is a deep muscle of the back. It can be divided by its superior attachments into thoracic, cervicis, and capitis.
- Attachments: Originates from the transverse processes of C4 – T10. The fibres ascend 4 – 6 vertebral segments, attaching to the spinous processes of C2 – T4 and to the occipital bone of the skull.
- Actions: Extends and contralaterally rotates the head and the vertebral column.
- Innervation: Posterior rami of the spinal nerves
- Blood Supply:
- Semispinalis thoracic receives its blood supply from the dorsal branches of posterior intercostal arteries.
- Semispinalis cervicis receives its blood from the occipital, vertebral and deep cervical arteries.
- Semispinalis capitis receives blood from the occipital artery.