Rectus capitis lateralis muscle

Origin and insertion

Rectus capitis lateralis is a short, flat muscle. It arises from the superior surface of the transverse process of the atlas (C1). The vertically oriented fibers travel superiorly to insert onto the inferior surface of the jugular process of the occipital bone.

Relations

Rectus capitis lateralis has several muscular and neurovascular relations. It is lateral to the rectus capitis anterior muscle and the cranial end of longus capitis. The levator scapulae muscle inserts on the opposite side of the C1 transverse process inferior to rectus capitis lateralis. Rectus capitis lateralis is also anterior to obliquus capitis superior, anterosuperior to obliquus capitis inferior and superior to anterior cervical intertransverse muscle. 

The rectus capitis lateralis is posteriorly related to the internal jugular vein. It is separated from this structure by the carotid sheath and occasionally by the accessory nerve (CN XI). The posterior belly of the digastric muscle is also anterior to the muscle; with the occipital artery sometimes separating the two structures. The vertebral artery passes by the medial border of the rectus capitis lateralis muscle as it exits the transverse foramen of the atlas. The glossopharyngeal, vagus and accessory nerves (CN IX-XI) pass over the anterior surface if rectus capitis lateralis as they exit the jugular foramen.

Innervation

Motor innervation to rectus capitis lateralis is provided by branches of the anterior rami of the first two cervical spinal nerves (C1-C2).

Blood supply

Branches arising from the ascending pharyngeal, vertebral and occipital arteries carry oxygenated blood to the rectus capitis lateralis muscle.

Function

The primary function of rectus capitis lateralis is to stabilize the atlanto-occipital joint during movement. Unilateral contraction produces ipsilateral flexion of the neck.