Splenius

(splenius capitis and splenius cervicis)

Origin = Ligamentum nuchae, inferior half; spinous processes of last cervical vertebrae and upper six thoracic vertebrae.

Insertion = Temporal bone, mastoid process; transverse processes of the first three cervical vertebrae.

Action =

One side - Lateral flexion and rotation to the same side of the cervical spine.

Both Sides - Extends and hyperextends the atlantooccipital joint and the cervical spine.