Which action is shared by Splenius capitis and Splenius cervicis?

Which action is shared by Splenius capitis and Splenius cervicis?

• A. Extends the head/neck
• B. Flexes the trunk
• C. Elevates the ribs
• D. Rotates the head to opposite side

Answer: (A)

Both Splenius capitis and Splenius cervicis function as neck extensors. Their fibers run from the lower cervical and upper thoracic spine up to the skull (capitis) and upper cervical vertebrae (cervicis). When both muscles contract together, they pull the head and neck backward, producing extension of the head/neck. Unilateral contraction would rotate and laterally flex the head to the same side, but the shared action asked about here is the extension produced by both contracting together. They do not flex the trunk or elevate the ribs, which are actions of other muscle groups.

Both Splenius capitis and Splenius cervicis function as neck extensors. Their fibers run from the lower cervical and upper thoracic spine up to the skull (capitis) and upper cervical vertebrae (cervicis). When both muscles contract together, they pull the head and neck backward, producing extension of the head/neck. Unilateral contraction would rotate and laterally flex the head to the same side, but the shared action asked about here is the extension produced by both contracting together. They do not flex the trunk or elevate the ribs, which are actions of other muscle groups.