Rectus capitis posterior major muscle

Origin and insertion

Rectus capitis posterior major muscle is triangular in shape. It attaches to the spinous process of axis (the second cervical vertebra) deep to obliquus capitis superior and semispinalis capitis muscles. Its fibres pass superolaterally, skipping the first cervical vertebra, to insert via a broader attachment on the lateral part of the inferior nuchal line and the occipital bone directly below it.

Relations

Rectus capitis posterior major is located lateral and superficial to rectus capitis posterior minor, and deep and medial to obliquus capitis superior. Also, rectus capitis posterior major muscle forms the superomedial boundary of the suboccipital triangle.

A soft tissue connection between rectus capitis posterior major and the cervical dura mater of the meninges in the atlantoaxial interspace has been described but this relationship hasn’t been studied enough to establish any clinical significance.

Innervation

Rectus capitis posterior major muscle, along with the other suboccipital muscles and semispinalis capitis, are innervated by suboccipital nerve (the first cervical posterior ramus).

Blood supply

Just like the other suboccipital muscles, rectus capitis posterior major receives its blood supply from the vertebral artery and deep descending branches of the occipital artery.

The vertebral vein is responsible for its venous drainage through the posterior external vertebral venous plexus.

Function

Rectus capitis muscle is involved in extension of the head on the neck. Working bilaterally, this muscle produces extension at the atlanto-occipital joints, while when working unilaterally it produces atlanto-axial rotation of the head (along with obliquus capitis inferior and splenius capitis) towards the ipsilateral side. Moreover, rectus capitis posterior major stabilizes the atlanto-occipital joint during movements making it an important postural muscle.