Splenius capitis muscle
The splenius capitis is a broad strap-like muscle located in the back of the neck. It lies in the superficial layer of the deep back muscles. The splenius capitis extends between the cervical and thoracic vertebrae and temporal and occipital bones of the skull.
The upper part of the muscle lies deep below the sternocleidomastoid, and it participates in forming the floor of the posterior neck triangle. The lower part of the splenius capitis is positioned underneath the trapezius. The splenius capitis is located superior to the semispinalis capitis and longissimus capitis muscles.
Origin: lower half of the nuchal ligament, spinous processes of the seventh cervical to the third thoracic vertebrae (C7 - T3).
Insertion: mastoid process of the temporal bone, external surface of the occipital bone below the lateral aspect of the superior nuchal line.
Action: bilateral contractions - extension of the head and neck; unilateral contractions - rotation and lateral flexion of the head and neck to the ipsilateral side.
Innervation: lateral branches of the dorsal rami of the second to third cervical spinal nerves (C2 - C3).
Blood supply: branches of the occipital artery.