Obliquus capitis superior muscle
Obliquus capitis superior, or superior oblique, is a small paired muscle located deep in the upper cervical region, at the base of the occipital bone. It is one of four muscles that comprise the suboccipital muscles group along with rectus capitis posterior major, rectus capitis posterior minor and obliquus capitis inferior.
This article will discuss the anatomy and function of obliquus capitis superior muscle.
|Origin||Transverse process of atlas|
|Insertion||Occipital bone (between superior and inferior nuchal lines)|
|Action||Bilateral contraction - Atlantooccipital joint: Head extension
Unilateral contraction - Atlantoaxial joint: Head lateral flexion (ipsilateral)
|Innervation||Suboccipital nerve (posterior ramus of spinal nerve C1)|
|Blood supply||Vertebral artery and descending branches of the occipital artery|
Origin and insertion
Obliquus capitis superior arises from the superior surface of transverse process of atlas (first cervical vertebra). This is also where one of the levator scapulae muscle slips originates from. The muscle becomes broader as it passes upward, travelling a short distance to insert between the superior and inferior nuchal lines on the external surface of occipital bone.
The insertion is located lateral to semispinalis capitis muscle and anterolateral to rectus capitis posterior major.
Obliquus capitis superior muscle is the most lateral of the suboccipital muscles, located superficially to the recti muscles and superiorly to the inferior obliquus muscle. It is also the smallest muscle of the suboccipital group.
Obliquus capitis superior forms the superolateral border of the suboccipital triangle where both the vertebral artery and the first cervical or suboccipital nerve are contained. Both longissimus capitis and splenius capitis overlap this muscle.
Similar to the other suboccipital muscles, obliquus capitis superior is innervated by the suboccipital nerve, this is the first cervical posterior (dorsal) ramus.
The vertebral artery and deep descending branches of the occipital artery provide blood supply for the obliquus capitis superior muscle and the other suboccipital muscles. Obliquus capitis superior muscle is drained by the vertebral vein through the posterior external vertebral venous plexus.
Working bilaterally, obliquus capitis superior extends the head on the neck at the atlanto-occipital joint. It laterally flexes the head to the ipsilateral side when working unilaterally. The muscles most prominent role is as a postural muscle, whereby it stabilizes the atlanto-occipital during head movements.