Which statement is true about Splenius capitis and Splenius cervicis?

Which statement is true about Splenius capitis and Splenius cervicis?

• A. They share origin, action, and innervation
• B. They share the same insertion but different innervation
• C. They have different origins and shared innervation
• D. They are not functionally related

Answer: (A)

The pair of Splenius muscles share similar actions and the same nerve supply, but they do not originate from the same places. Splenius capitis starts from the ligamentum nuchae and the spinous processes of C7 through T4, and it inserts on the mastoid part of the temporal bone and the superior nuchal line. Splenius cervicis, on the other hand, originates from the spinous processes of T3 through T6 and inserts on the transverse processes of the upper cervical vertebrae (C1–C3, sometimes C4). Both muscles are innervated by the dorsal rami of the cervical spinal nerves and both act to extend the head and neck when acting together; when acting unilaterally, they rotate and laterally flex the neck to the same side. Because their origins and insertions are not the same, but their innervation and general actions are shared, the correct relation is that they have different origins and shared innervation. The option stating they share origin is not accurate, and the other statements don’t fit the anatomical reality as well.

The pair of Splenius muscles share similar actions and the same nerve supply, but they do not originate from the same places. Splenius capitis starts from the ligamentum nuchae and the spinous processes of C7 through T4, and it inserts on the mastoid part of the temporal bone and the superior nuchal line. Splenius cervicis, on the other hand, originates from the spinous processes of T3 through T6 and inserts on the transverse processes of the upper cervical vertebrae (C1–C3, sometimes C4). Both muscles are innervated by the dorsal rami of the cervical spinal nerves and both act to extend the head and neck when acting together; when acting unilaterally, they rotate and laterally flex the neck to the same side.

Because their origins and insertions are not the same, but their innervation and general actions are shared, the correct relation is that they have different origins and shared innervation. The option stating they share origin is not accurate, and the other statements don’t fit the anatomical reality as well.