Splenius capitis muscle
The splenius capitis originates from the first, second, and third thoracic vertebrae, T1-T3. It attaches to the spinous processes of T1-T3, the supraspinous ligament above these vertebrae, and the lower portion of the nuchal ligament.
Unilateral contraction of the splenius capitis leads to an extension of the head while bilateral contraction leads to rotation and ipsilateral bending of the head.
The splenius capitis muscle is innervated by the dorsal rami of the third and fourth cervical spinal nerves.
The splenius capitis muscle receives blood through the muscular branches of the aorta.