Quick Facts
Origin: Nuchal ligament, spinous processes of C7-T2 and T11-L3 vertebrae.
Insertion: Spinous processes of C2-C4 and T2-T8 vertebrae.
Action: Extends and laterally flexes neck and trunk.
Innervation: Posterior rami of lower cervical and upper thoracic nerves.
Arterial Supply: Occipital, deep cervical, and vertebral arteries, dorsal branches of posterior intercostal, subcostal, and upper lumbar arteries.
Related parts of the anatomy
Origin
The spinalis muscles originate from the:
- nuchal ligament;
- spinous processes of the seventh cervical to second thoracic and eleventh thoracic to third lumbar vertebrae.
There can be variations between individuals regarding the origin sites for the spinalis muscles (Tubbs, Shoja and Loukas, 2016).
Insertion
The fibers of the spinalis muscles travel superiorly along the posterior neck and upper back regions and insert onto the spinous processes of the axis (second cervical vertebra) to fourth cervical and second to eighth thoracic vertebrae. There can be variations between individuals regarding the insertion sites for the spinalis muscles (Tubbs, Shoja and Loukas, 2016).
Key Features & Anatomical Relations
Overall, the spinalis muscles are the most medial of the erector spinae. They are intrinsic muscles of the back and are found along the back and posterior neck regions. They are long, flat skeletal muscles that are composed of two parts:
- spinalis colli, which is the superior portion;
- spinalis thoracis, which is the inferior portion.
In some individuals, there is a third part, known as the spinalis capitis, which, blends with the semispinalis capitis muscle (Greiner, Bedford and Walker, 2004).
The spinalis muscles are located:
- superficial to the semispinalis and multifidus muscles;
- deep to the splenius capitis, splenius colli, trapezius, latissimus dorsi, and serratus posterior inferior muscles, and the thoracolumbar fascia;
- medial to the longissimus muscle.
Actions
Overall, the spinalis muscles are involved in multiple actions:
- during unilateral contraction, they laterally flex the neck and trunk to the same side;
- during bilateral contraction, they extend the neck and trunk (Moore, Dalley and Agur, 2009).
References
Greiner, T. M., Bedford, M. E. and Walker, R. A. (2004) 'Variability in the human M. spinalis capitis and cervicis: frequencies and definitions', Annals of Anatomy - Anatomischer Anzeiger, 186(2), pp. 185-191.
Moore, K. L., Dalley, A. F. and Agur, A. M. R. (2009) Clinically Oriented Anatomy. Lippincott Williams & Wilkins.
Tubbs, R. S., Shoja, M. M. and Loukas, M. (2016) Bergman's Comprehensive Encyclopedia of Human Anatomic Variation. Wiley.
