头长肌（longus capitis muscle）

  

  

  

Origin

The longus capitis muscle is an anterior vertebral muscle and originates from four slender tendons (in line with those of the anterior scalene muscle) from the anterior tubercles of C3 - C6 transverse processes.

Insertion

The longus capitis muscle inserts in to the basilar part of the occipital bone that is the wedge-like portion of the occipital bone that lies anterior to the foramen magnum. At their insertion at the basiocciput the longus capitis muscles lay adjacent to one another alongside the pharyngeal tubercles.

Relations

The prevertebral fascia extends from the base of the skull in front of the longus capitis and rectus capitis lateralis muscles, it extends as far inferiorly as the lower limit of the longus colli muscle at the body of the T3 vertebra.

Retropharyngeal lymph nodes lie at the level of the lateral mass of the atlas and along the lateral aspect of the longus capitus muscles.

The anterior ramus of C1 emerges lateral to the atlanto-occipital joint then passes between the rectus capitis anerior and rectus capitis lateralis muscles before penetrating and supplying the longus capitis muscle. The nerve then gives a branch to the hypoglossal nerve.

Blood supply

The longus capitis muscle receives its blood supply from muscular branches of the ascending cervical artery and the inferior thyroid artery.

Nerve supply

The longus capitis muscle is innervated by anterior rami of the C1 to C3 spinal nerves from the cervical plexus.

Action

The longus capitis muscle works synergistically with longus colli and scalene muscles as a weak flexor of the head and cervical spine. The action of the muscle is assisted by gravity and by the powerful sternocleidomastoid muscles.