WebOrigin: On the spines of the last fourthoracic vertebrae Insertion: Both the spines of the most cranial thoracic vertebrae and the cervical vertebrae Artery: Lateral sacral artery Nerve: Posterior branch of spinal nerve Action: Extends thevertebral column Antagonist: Rectus abdominis muscle Description: The Sacrospinalis (Erector spinae) and ...